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14th International Symposium on

Functional π-Electron Systems

2nd - 7th June 2019

Campus Adlershof I Berlin I Germany www.fpi14.de

Abstracts Oral Presentations

9:00 - 9:45 Plen.

9:45 - 10:30 Plen.

Wista Convention Center Bunsen Hall Wista Convention Center Einstein-Newton-Cabinet Erwin-Schrödinger-Zentrum Conference Room 0'119

10:30 - 11:00 00:30

Emil List-Kratochvil Stefan Hecht Julia Stähler

11:00 - 11:30 Inv.

Chihaya Adachi

Kyushu U

Optical and electrical excitation of organic semiconductor laser diodes

Uwe Bunz

U Heidelberg

N-Heteroacenes and N-Heteroarenes as Novel Materials

Denis Andrienko

MPI Mainz

Molecular understanding of organic-organic interfaces and mixtures

11:30 - 11:50 Contr.

Zuo-Quan Jiang

Soochow U

Highly Efficient Thermally Activated Delayed Fluorescence (TADF) Emission Based on Multi-π-Systems

Robert Twieg

Kent State U

Discotic Liquid Crystals Do NOT Require Tails

Micaela Matta

Northwestern U

Optimization of donors and acceptors for organic photovoltaics guided by molecular simulations

11:50 - 12:10 Contr.

Juoza Vidas Grazulevicius

Kaunas U

Exciplex-forming systems for efficient organic light-emitting diodes

Hironobu Hayashi

NAIST

On-surface light-induced synthesis of higher acenes from α-diketone-type precursors

Hiroyuki Yoshida

Chiba U

Organic-organic interface and energy of charge separation states in the film of donor and acceptor blends

12:10 - 12:30 Contr.

Daniel Congrave

U Cambridge

A design rule for obtaining efficient near-IR TADF emission beyond 1000 nm

Andrej Jancarik

CAS

A practical general method for the preparation of long acenes

Egbert Zojer

Graz U

Embedded dipole SAMs for tuning electrode work functions

12:30 - 14:00 01:30

Uwe Bunz Chihaya Adachi Andreas Opitz

14:00 - 14:30 Inv.

Chunyan Chi

NU Singapore

Acenes and Extended Heterocyclic Quinodimethanes

Paul Blom

MPI Mainz

Predictive Modelling of Charge Transport in Organic Semiconductors

Soo Young Park

Seoul NU

Color-Specific Photoswitching in Dual Color Fluorescent System

14:30 - 14:50 Contr.

Yi Liu

LBNL

Stable para-Quinodimethane Derivatives for Optoelectronics

Hiroko Yamada

NAIST

Engineering Thin Films of a Tetrabenzoporphyrin toward Efficient Charge-Carrier Transport

Robert Göstl

DWI

Tailor-making π-extended optical force probes for stress sensing in materials

14:50 - 15:10 Contr.

Anjan Bedi

U Jerusalem

Helically-Locked Tethered Twistacenes

Karin Zojer

Graz U

Controlling carrier type and contact resistances in organic thin-film transistors

Takashi Nakanishi

WPI-MANA

Alkylated-π Functional Molecular Liquids toward Stretchable Electret Applications

15:10 - 15:30 Contr.

Luca Beverina

U Milan

Bench-top, sustainable access to conjugated materials: how far you can go with tap water, a stirring plate, very little palladium and a little soap

Maria Diaz-Garcia

U Alicante

Novel organic compounds for solution-processed thin film organic lasers

Liqiang Li

Tianjin U

Semiconductor/conductor interface piezoresistive effect for novel pressure sensor with tunable sensitivity

15:30 - 16:00 00:30

Chunyan Chi Stefan Hecht Thuc-Quyen Nguyen

16:00 - 16:30 Inv.

Iain McCulloch

KAUST

Semiconducting Polymers for High Performance OFET and OECT Applications

Ben Zhong Tang

Hong Kong U

Room Temperature Phosphorescence

Natalie Banerji

U Bern

Ultrafast Properties of a Self-Doped Conjugated Polyelectrolyte

16:30 - 16:50 Contr.

Mao Li

CIAC

Electrochemical Synthesis of Functional Polymers

Zhongfu An

Nanjing Tech U

Ultralong Organic Phosphorescence

Philip Chow

Hong Kong U

Charge generation dynamics in efficient non-fullerene organic solar cells

16:50 - 17:10 Contr.

Yousuke Ooyama

Hiroshima U

Synthesis, Optical and Electrochemical Properties of Phenanthrodithiophene (Fused-Bibenzo[c]thiophene) Chromophore

Matthias Stolte

U Würzburg

Ultra-narrow Bandwidth Organic Photodiodes by Exchange Narrowing in Merocyanine H

‑

and J-aggregate Excitonic Systems

Till Biskup

U Freiburg

Electronic structure, morphology, and flexibility of conjugated polymers:Insights from time-resolved electron paramagnetic resonance spectroscopy

17:10 - 17:30 Contr.

Xike Gao

SIOC

Azulene-Based Organic Semiconductors

Peter Strohriegl

U Bayreuth

Crosslinkable conjugated polymers for organic electronics

Yuqian Jiang

NCNST China

Understanding the microscopic mechanisms of carrier and exciton transport in organic semiconductors

17:30 - 17:50 Contr.

Michael Sommer

TU Chemnitz

N-type copolymers for organic solar cells, transistors and thermoelectrics

Jacek Ulanski

Lodz U

Printed Organic Electronics – Problems and Perspectives

Ergang Wang

Chalmers U

Molecular Design and Synthesis towards High-performance All-Polymer Solar Cells

from 18:30

MondayWista Convention Center Bunsen Hall

Coffee Break

Poster Session

Thuc-Quyen Ngyuen

UCSB

Understanding Loss Mechanisms in Bulk Heterojunction (BHJ) Organic Solar CellsSession Chair: Norbert Koch

Klaus Müllen

MPI Mainz

Graphene Nanoribbons are Unique SemiconductorsSession Chair: Stefan Hecht

Coffee Break

Lunch

Session Chairs:

Session Chairs:

Session Chairs:

9:00 - 9:45 Plen.

9:45 - 10:30 Plen.

Wista Convention Center Bunsen Hall Wista Convention Center Einstein-Newton-Cabinet Erwin-Schrödinger-Zentrum Conference Room 0'119

10:30 - 11:00 00:30

Natalie Banerji Luca Beverina Patrick Amsalem

11:00 - 11:30 Inv.

Natalie Stingelin

Georgia Tech

Designing solution-processed photonic light- and heat-management structures for solution-processable and printable organic optoelectronic devices

Peter Bäuerle

U Ulm

Towards complex 3D carbon-sulfur structures

Satoshi Kera

NINS

Evolution of π orbital state upon assembling the molecules on the surface

11:30 - 11:50 Contr.

Han Young Woo

Korea U

Aqueous-processable organic photovoltaic materials and devices

Mihaela Stefan

UT Dallas

Thienopyrrole organic semiconductors for organic field effect transistors (OFETs)

Jianxin Tang

Soochow U

Efficient CsPbBr3 Perovskite Light-Emitting Diodes Enabled by Synergetic Device Architecture

11:50 - 12:10 Contr.

Chuanlang Zhan

Hebei U

Designing Quaternary Blended Organic Solar Cells with Over 13% Efficiencies

Brigitte Holzer

TU Vienna

Mixed Sulfur/Selenium Fused π-Conjugated Materials for Organic Field-Effect Transistors

Yasuo Nakayama

Tokyo U

Valence band dispersion of epitaxial perfluoropentacene on pentacene single crystals

12:10 - 12:30 Contr.

Alexander Kuehne

Ulm U

Bio-degradable conjugated polymer particles as bio-medical imaging probes

Sigurd Höger

U Bonn

Synthesis and Properties of Molecular Spoked Wheels

Anirudh Sharma

U Bordeaux

Tuning the Interfacial Electronic Properties for High-Performance Perovskite Solar Cells

12:30 - 14:00 01:30

Ian McCulloch Giovanni Ligorio Denis Andrienko

14:00 - 14:30 Inv.

Christine Luscombe

U Washington

Polythiophene derivatives as mixed organic ionic and electronic conductors

Jianbin Xu

CU Hong Kong

Adventure of Electroactive/Photoactive Organic Thin Films on Flatland

Zhigang Shuai

Tsinghua U

Modeling electronic processes in organic materials: organic phosphorescence and organic thermoelectrics

14:30 - 14:50 Contr.

Paul Burn

U Queensland

Dielectric constant tuning of organic photovoltaic materials

Jose Segura

U Madrid

Development of Novel Covalent Organic Frameworks

Noboyuki Matsuzawa

Panasonic Corp.

Massive theoretical design of hole conducting organic materials by using cloud computing environment

14:50 - 15:10 Contr.

Anna Österholm

Georgia Tech

Disentangling Redox Properties and Capacitance in Soluble Conjugated Polymers for Electrochemical and Bioelectronic Applications

Benlin Hu

MPI Mainz

The 2D and 3D extension of long pyrene-fused N-heteroacenes

Przemyslaw Data

Silesian U

Thermally Activated Delayed Fluorescence vs Room Temperature Phosphorescence how to control opposite processes in the same molecule and use in OLEDs

15:10 - 15:30 Contr.

Giovanni Costantini

U Warwick

Microstructure and sequence of conjugated polymers revealed by high-resolution scanning probe microscopy

Elena Mena-Osteritz

Ulm U

Thiophene-based S,N-Heteroacenes: Electronic Properties and X-Ray Structure Analysis

Patrick Serafini

PU Milan

Molecular modeling of hybrid sp-sp2 carbon-based nanostructures: structural, electronic and vibrational properties

15:30 - 16:00 00:30

Paul Blom Natalie Stingelin Jianbin Xu

16:00 - 16:30 Inv.

Kilwon Cho

Pohang U

Bias-Stress-Induced Charge Trapping in Organic Transistors: A Molecular Structure Perspective

Elizabeth von Hauff

VU Amsterdam

A dynamic picture of photovoltaic energy conversion

Satish A. Patil

IIsc

Exceeding Shockley–Queisser Limit with Singlet Fission

16:30 - 16:50 Contr.

Takehiko Mori

TI Tech

Transistors of charge-transfer complexes

Itaru Osaka

Hiroshima U

Efficient “Sensitized” Ternary Polymer Solar Cells with Small Photon Energy Loss

David Jones

U Melbourne

Liquid crystallinity as a self-assembly motif for solid state singlet fission materials

16:50 - 17:10 Contr.

Marta Mas-Torrent

ICMAB

Fabrication of reproducible and reliable organic field-effect transistors by solution-shearing employing blended organic semiconductors

Gjergji Sini

U of Cegy-Pontosie

Charge Separation in Organic Solar Cells: Energy Bending versus Energy Disorder

David Rais

IMC

Singlet fission phenomenon: quantifying “dark” triplet states in organic semiconductors

17:10 - 17:30 Contr.

Yunlong Guo

ICCAS

Ultraflexible photodetectors based on organic field-effect transistors

Giulia Grancini

EPFL

2D/3D Hybrid Perovskite Interfaces and Physics therein for Stable and Efficient Solar Cells

Rowen MacQueen

HZB

Hybrid lead halide perovskite as a non-excitonic triplet sensitiser for triplet fusion upconversion

17:30 - 17:50 Contr.

Paschalis Gkoupidenis

MPI Mainz

Neuromorphic synchronization of organic electrochemical devices

Laurence Lutsen

Hasselt U

Towards 2D Layered Hybrid Perovskites With Enhanced Functionality

Isaac Alcon

DTU

Spatial control of electrical currents in nano-porous graphene by chemical engineering

from 18:30

TuesdayWista Convention Center Bunsen Hall

Coffee Break

Poster Session

Antoine Kahn

Princeton U

Paradigm Shift in n-Doping of Low Electron Affinity Organic SemiconductorsSession Chair: Norbert Koch

He Henry Yan

Hong Kong U

Achieving non-fullerene organic solar cells with over 16% efficiency: material design, device optimization and mechanism studySession Chair: Norbert Koch

Coffee Break

Lunch

Session Chairs:

Session Chairs:

Session Chairs:

9:00 - 9:45 Plen.

9:45 - 10:30 Plen.

Wista Convention Center Bunsen Hall Wista Convention Center Einstein-Newton-Cabinet Erwin-Schrödinger-Zentrum Conference Room 0'119

10:30 - 11:00 00:30

Peter Bäuerle Elena Mena-Osteritz Satish Patil

11:00 - 11:30 Inv.

Stefan Mannsfeld

TU Dresden

Solution-shearing: getting more out of an already quite standard coating method for organic field effect transistors

Shigehiro Yamaguchi

Nagoya U

Main-group-containing π-electron materials with structural constraint

Anna Köhler

U Bayreuth

What is the binding energy of a charge transfer state in an organic solar cell?

11:30 -11:50/

12:00

Marcus Halik (invited - 30 min.)

U Erlangen-Nürnberg

The impact of the molecular structure of in-plane self-assembled p-systemson their 2D-molecular order and their transport properties

Michael Mastalerz (contr. - 20 min.)

U Heidelberg

From Simple Anthracene to Structurally Defined Perylene- and Coronene Nanoribbons

Fengling Zhang (contr. - 20 min.)

Linköping U

On Mechanism of hole transfer in Non-fullerene (NF) Organic Solar Cells

11:50/

12:00-

12:10/

12:20Contr.

Xuediao Cai

Shaanxi Normal U

Preparation of fused heterocyclic conjugated polymers by multicomponent one-pot polymerization

Aurelio Mateo-Alonso

POLYMAT

Synthesis of giant monodisperse n-doped nanographenes

Safa Shoaee

U Potsdam

Decoding Charge Recombination Through Charge Generation

12:10/

12:20-

12:30/

12:40Contr.

Yutaka Ie

Osaka U

Development of Organic Semiconductors Containing Fluorine-Substituted Electron-Accepting Units for Organic Photovoltaics

Christoph Lambert

U Würzburg

Changing optical properties stepwise from oligomeric to polymeric squaraine dyes

Ying Wang

TIPC

Experimental Evidence for “Hot Exciton” Thermally Activated Delayed Fluorescence Emitters

12:30 - 14:30 01:30

from 14:30

WednesdayWista Convention Center Bunsen Hall

Social Events

(Berlin City Tour, Guided Tour of Campus Adlershof)

George Malliaras

U Cambridge

Interfacing with the Brain Using Organic ElectronicsSession Chair: Norbert Koch

Lynn Loo

Princeton U

Understanding how hierarchical structure impacts charge transport in molecular and polymeric semiconductorsSession Chair: Norbert Koch

Coffee Break

Lunch

Session Chairs:

Inv.

Contr.

9:00 - 9:45 Plen.

9:45 - 10:30 Plen.

Wista Convention Center Bunsen Hall Wista Convention Center Einstein-Newton-Cabinet Erwin-Schrödinger-Zentrum Conference Room 0'119

10:30 - 11:00 00:30

Felix Hermerschmidt Ben Zhong Tang Karin Zojer

11:00 - 11:30 Inv.

John Reynolds

Georgia Tech

Fade to Black: Color Control in Electrochromic Polymers

Ming Lee Tang

U California

Energy conversion with synergistic combinations of acenes and quantum dots

David Beljonne

U Mons

Modeling charge transport and recombination in conjugated polymer heterojunctions

11:30 -11:50/

12:00

Seth Rasmussen (contr. - 20 min.)

North Dakota State U

Ambipolar-Acceptor Frameworks as a New Design Paradigm in Low Bandgap Polymers

Ken Albrecht (contr. - 20 min.)

Kyushu U

Thermally-Activated Delayed-Fluorescence Dendrimers that Realizes OLEDs with Fully Solution-Processed Organic-Layers

Oliver Hofmann (invited-30 min.)

Graz U

Charge transfer beyond the first monolayer: Fact or Fiction?

11:50/

12:00-

12:10/

12:20Contr.

Masayuki Gon

Kyoto U

Near-Infrared-Emissive Conjugated Polymers Based on Fused Azobenzene Complexes

Shigeyuki Yagi

Osaka U

Phosphorescent organometallic dendrimers for non-doped organic light-emitting diodes

Yuanping Yi

ICCAS

Theoretical Study of the Energy Loss Mechanisms for Organic Photovoltaics

12:10/

12:20-

12:30/

12:40Contr.

Ullrich Scherf

U Wuppertal

Ladder Polymers made of Pentacyclic Building Blocks linked by Exocyclic Double Bonds

Haiming Zhang

Soochow U

On-Surface Synthesis of 8- and 10-Armchair Graphene Nanoribbons

Feng He

SUSTech

Chlorination: A Facile Method for Efficient Solar Conversion

12:30 - 14:00 01:30

John Reynolds Dieter Neher Satoshi Kera

14:00 - 14:30 Inv.

John Anthony

U Kentucky

Small molecule design for organic electronics

Harald Ade

NCSU

Rational Strategies to Stabilize the Morphology of Non-Fullerene Organic Solar Cells

Jana Zaumseil

U Heidelberg

Tuning Transport and Emission Properties of Polymer-Sorted Carbon Nanotube Networks

14:30 - 14:50 Contr.

Guillaume Schweicher

U Cambridge

Chasing the ‘killer’ phonon mode for the rational design of low disorder, high mobility molecular semiconductors

Julien Gorenflot

KAUST

Charge dissociation at organic heterojunctions: interface roughness versus ultrafast delocalization

Giovanni Ligorio

HU Berlin

Modular sensor platform based on electrolyte-gated organic field-effect transistor from biomolecules (glucose and urea) to nitroaromaticexplosive (DNT, TNT) detection

14:50 - 15:10 Contr.

Michael Wolf

U British Columbia

Photofunctional sulfur-bridged oligomers and polymers

Mats Andersson

Flinders U

Morphology and transition temperatures of conjugated polymer blends for solar cells

Yuli Huang

NU Singapore

Selective self-assembly of 2,3-diaminophenazine molecules on MoSe 2 mirror twin boundaries

15:10 - 15:30 Contr.

Toshiki Higashino

AIST

Development of Layered-Crystalline BBBT-based Organic Semiconductor Materials with Long Alkyl Chain

Gitti Frey

Technion

Microscopy Imaging and 3D-tomography of organic solar cell bulk heterojunction

Bert Nickel

LMU

Organic semiconductor film transfer for 3D/2D hybrid devices

15:30 - 16:00 00:30

Stefan Hecht Charlotte Gers-Panther/ Katharina Franke Emil List-Kratochvil

16:00 - 16:30 Inv.

Paolo Samori

Strasbourg U

Taming complexity in polymer opto-electronics: tailoring multifunctional devices and chemical sensors

Marcel Mayor (Wiley Lecture)

U Basel

Chiral Carbon Architectures

Joseph Shinar

Iowa State U

Nature of Photogenerated Defects in Bulk Heterojunction OPVs

16:30 - 16:50 Contr.

Yanli Tang

Shaanxi Normal U

Functional Conjugated Polymers-Based Biosensors and Bioanalysis

Austin Jones

Georgia Tech

Investigating Acceptor Gradient Polymer Donors for Non-fullerene Organic Solar Cells

Claudia Tait

FU Berlin

Insights into p-doping of P3HT by Electron Paramagnetic Resonance

16:50 - 17:10 Contr.

Wojciech Pisula

Lodz U

Interfacial Film Morphology in Ultrathin Organic Field-Effect Transistors

Jaume Veciana

ICMAB

Electronic transport through organic spin-containing molecules and their use for manipulating electronic properties of surfaces

Ellen Moons

Karlstad U

How does photo-oxidation of materials affect solar cell performance?

17:10 - 17:30 Contr.

Deqing Zhang

ICCAS

Optically tunable FETs with semiconducting conjugated polymers entailing azobenzene groups in the side chains

Xiangnan Sun

NCNST

Multipurpose Molecular Spintronic Device

Linda Peteanu

Carnegie Mellon U

Enhanced Photo-stability of Organic Molecules Through Plasmonic Effects

17:30 - 17:50 Contr.

Fengjiao Zhang

Chinese Academy of Science

Construction of Organic Thin-film Transistors for Multiple Sensing Applications

Ferdinand Grozema

Delft U

Quantum Interference Effects in Charge Transfer and Single Molecule Conductance

Bernd Strehmel

Niederrhein U

New NIR-LEDs, NIR Lasers with Line-Shaped Fokus and Functionalized Cyanines Facilitate Synthesis of Tailor Made Polymers and Their Use in Industry 4.0 Related Applications

Session Chairs:

Session Chairs:

Session Chairs:

18:00

from 19:00

ThursdayWista Convention Center Bunsen Hall

Symposium Dinner

Coffee Break

Departure Symposium Dinner

Jean-Luc Bredas (Thieme Lecture)

Georgia Tech

Two-dimensional π-conjugated Covalent Organic Frameworks (COFs): Emergence of high charge-carrier mobilities and magnetic propertiesSession Chair: Michael Mastalerz

Luisa Torsi

U Bari

Single-molecule label-free large-area bioelectronic sensing of clinical biomarkers Session Chair: Claudia Draxl

Coffee Break

Lunch

Inv.

Contr.

Wista Convention Center Bunsen-Hall Wista Convention Center Einstein-Newton-Cabinet Erwin-Schrödinger-Zentrum Conference Room 0'119

Paolo Samori Xiaomin Xu Bert Nickel

9:00 - 9:30 Inv.

Karl Leo

TU Dresden

Conductivity of small-molecule organic semiconductors

Sylke Blumstengel

HU Berlin

Tuning opto-electronic properties of semiconductor surfaces with conjugated molecules

Tomas Torres

U Madrid

Subphthalocyanines and related compounds: Singular aromatic non-planar molecules

9:30 - 9:50 Contr.

Kenichi Nakayama

Osaka U

Carrier mobility measurement by MIS-CELIV method in hole-transport material for organic light-emitting diodes

Yusuke Ishigaki

Hokkaido U

Hyper covalent bond in highly strained hydrocarbon: an expandable C–C single bond with a bond length beyond 1.8 Å

Akihiko Fujii

Osaka U

Epitaxial growth and anisotropic properties of uniaxially oriented thin films utilizing polymorphic alkyl-substituted phthalocyanines

9:50 - 10:10 Contr.

Ross Warren

U Oxford

The Effect of Energy Levels on Doping processes in Organic Semiconductors

Tatiana Martins

Goiás U

Self-Assembled Phe-Phe Dipeptide Doped with Luminescent Compounds: Tunnable Photophysical Characteristics

Fengjiao Zhang

U Illinois

Solution-Processed Nanoporous Organic Thin Film Transistors

10:10 - 10:30 Contr.

James Ponder

Imperial College

Electrical and Thermal Transport Properties of Chalcogenophene Copolymers: Exploring the Effects of Monomers and Dimers from Furan to Tellurophene

Aikaterini Andreopoulou

U Patras

Development of Hybrid Materials based on Organic Semiconductors and Carbon Nanostructures or Inorganic Nanoparticles

Thomas Müller

U Düsseldorf

Dithieno[1,4]thiazines and Bis[1]benzothieno[1,4]thiazines – Redox Activity, Luminescence Characteristics and Antiaromaticity of Novel Congeners of Phenothiazine

10:30 - 11:00 01:30

11:00 - 11:45 Plen.

11:45 - 12:30 Plen.

01:30

13:30 - 15:00Guided tour Synchroton Bessy II

(Helmholtz-Zentrum Berlin)

Wista Convention Center Bunsen-Hall

12:30

Friday

Alberto Salleo

Stanford U

A polymer synapse for low-power neuromorphic computingSession Chair: Norbert Koch/ Stefan Hecht

Seth Marder

Georgia Tech

Development of Redox Dopants for Organic Semiconductors and Interface ModificationSession Chair: Norbert Koch/ Stefan Hecht

Coffee Break

Farewell

Session Chairs:

Functional π-Electron Systems14th International Symposium on

Abstracts Poster Presentation

Plenary Lectures

Monday, June 3rd

Understanding Loss Mechanisms in Bulk Heterojunction (BHJ) Organic Solar Cells

Thuc-Quyen Nguyen

Center for Polymers and Organic Solids and the Department of Chemistry & Biochemistry, University of California, Santa Barbara, CA 93106, USA

E-mail: quyen@chem.ucsb.edu

Organic bulk heterojunction (BHJ) solar cells require energetic offsets between the donor and acceptor to obtain high short circuit currents (JSC) and fill factors (FF). However, it is necessary to reduce the energetic offsets to achieve high open-circuit voltages (VOC). Recently, reports have highlighted BHJ blends which are pushing at the accepted limits of energetic offsets necessary for high efficiency. How the energeticoffset impacts the solar cell characteristics such as charge generation and recombination remains poorly understood. In this talk, I will discuss a comprehensive characterization of the losses in polymer:fullerene and polymer:nonfullerene BHJ blends, that achieve high VOC with low energy losses from the energy of absorbed photons. Despite the low energetic offset, these systems generate charge efficiently. The low electronic disorder in the blend allows efficient electron-hole separation even in the absence of a strong energetic driving force. These results hold promise that given the appropriate morphology, the JSC, VOC, and FF can all be improved, even with very low energetic offsets. I will also discuss the use of impedance-photocurrent device analysis (IPDA) toquantitatively characterize the competition between charge extraction and charge recombination under steady state operational conditions. Answering the fundamental question regarding charge generation/recombination across donor/acceptor interfaces allows for continued development of improved organic solar cell devices and photodetectors.

Graphene Nanoribbons are Unique Semiconductors

Klaus Müllen

Max Planck Institute for Polymer Research, Mainz, Germany

Graphenes and graphene nanoribbons (GNRs), their geometrical cutouts, are exciting additions to

the rich carbon family. Graphenes hold enormous promise, for example, in energy technologies and

non-linear optics. However, before they can be employed in electronics and their high charge-carrier

mobility be utilized in field-effect transistors (FETs), an opening of their band gaps must be achieved.

The best answer to this longstanding problem are GNRs, and this brings precision polymer synthesis

into play. While protocols from lithography or unzipping of carbon nanotubes offer no control over

length, width and edge structure, bottom-up synthesis is the method of choice.

We present unprecedented syntheses proceeding in, both, solution and on-surface. The latter

approach, which can be scaled up by extension from UHV-conditions to chemical vapor deposition,

also allows in-situ monitoring and proof of GNR-formation by scanning tunneling microscopy.

Based on these material breakthroughs, we fabricate FETs from single GNRs and GNR-networks and

compare the performance with that of conventional conjugated polymers. Surprisingly, the design of

GNRs with appropriate combinations of arm-chair and zig-zag edges furnishes robust topological

insulators in 2D as well as spin states with high correlation times. There is hope that these features

provide entries into spintronics and even quantum computing.

Science 2016, 351, 957; Nature 2016, 531, 489; J. Amer. Chem. Soc. 2018, 140, 9104; Angew. Chem. Int. Ed. 2018, 57,

11233; Nature 2018, 557, 557, 691; Nature Commun. 2018, 9(1); Nature 2018, 560, 209; Nature 2018, 561, 507.

Functional π-Electron Systems14th International Symposium on

Abstracts Poster Presentation

Invited Lectures

Monday, June 3rd

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Optical and electrical excitation of organic semiconductor laser diodes

Atula S. D. Sandanayaka1,2, Toshinori Matsushima1,2,3, Fatima Bencheikh1,2, Shinobu Terakawa1,2, William J. Potscavage, Jr.1,2, Chuanjiang Qin1,2, Takashi Fujihara4,5, Kenichi

Goushi1,2,3, Jean-Charles Ribierre1,2, and Chihaya Adachi1–5*

1 Center for Organic Photonics and Electronics Research (OPERA), Kyushu University, 744 Motooka,

Nishi, Fukuoka 819-0395, Japan 2 Japan Science and Technology Agency (JST), ERATO, Adachi Molecular Exciton Engineering Project

3 International Institute for Carbon Neutral Energy Research (WPI-I2CNER) 4 Innovative Organic Device Laboratory, Institute of Systems, Information Technologies and

Nanotechnologies (ISIT), 4-1 Kyudai-shinmachi, Nishi, Fukuoka 819-0388, Japan. 5 Fukuoka i3-Center for Organic Photonics and Electronics Research (i3-OPERA), 5-14 Kyudai-

shinmachi, Nishi, Fukuoka 819-0388, Japan.

-In this study, we investigated the lasing properties of 4,4’-bis[(N-carbazole)styryl]biphenyl

(BSBCz) thin films under optical and electrical pumping. The device architecture incorporated a

mixed-order distributed feedback SiO2 grating in an organic light-emitting diode structure and emitted

blue narrowed emission under the both excitations. We clarified that a BSBCz layer has clear

separation of the lasing wavelength from significant triplet and polaron absorption and design of a

proper feedback structure to suppress optical losses. We believe that this study represents an

important advance in organic semiconductor laser diode (OSLD) technology.

This is the last line of your abstract.

[1] (a) U. H. F. Bunz, J. U. Engelhart, B. D. Li ndner, M . Scha ffr oth, Angew. Chem. 5 2, 381 0-3 821 (2013 ). (b) U. H. F. Bunz, Acc. Che m. Re s. 48, 1 676 (2015 ).[2] H. Reiss, L. Ji, J. Han, S. Koser, O. Tverskoy, J. Freude nberg, F. Hinkel, M. M oos, A. Friedri ch, I. Kr umme nacher, C. La mbert, H. Braunschweig, A. Dreuw, T. Marder, U. H. F. Bunz, Angew. Che m. 57, 9 543 (2018 ).[3] E. C. Rüdiger, M. Müller, S. Koser, F. Romi nger, J. Freudenberg, U. H. F. Bunz, Che m. Eur. J. 24, 10 36 (2018 ). [4]M. Müller, E. Rüdiger, S. Koser, O. Tverskoy, F. Rominger, F. Hinkel, J. Freude nberg, U. H. F. Bunz, Chem. Eur. J. 24, 8087 (201 8).[5] M. Müller, H. Reiss, O. Tversk oy, F. Rominger, J. Freude nberg, U. H. F. Bunz Che m. Eur. J. 24, 1 2801 (201 8).

[6] D. B. Xia, X. G uo, L. Chen, M. Baumgarten, A. Keerthi, K . Müllen, Angew. Che m. 55, 9 41 (2 016 ).

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1 N-Heteroacenes and N-Heteroarenes as Novel Materials 2 3 Uwe H. F. Bunz1 and Jan Freudenberg1

4 5 1Organisch-Chemisches Institut, Ruprecht-Karls-Universität Heidelberg, Im Neuenheimer Feld 270,

6 69120 Heidelberg (FRG)

7 8 N-Heteroacenes and N-heteroarenes [1] are attractive targets both structurally but also as potential 9 materials for organic electronics, particularly if fourfold halogenated. [2] A powerful concept we

10 have recently employed is the addition of four benzo-groups towards the core of acenes and 11 azaacenes. In both cases now azaheptacenes and heptacenes are easily prepared and are fully 12 stable. In cases where there is only one butterfly wing attached to the molecule we obtain a mono-13 butterfly-wing protected acene that shows mobilities of up to 0.2 cm2/Vs. [3]

These materials are all synthesized starting from tetrabromoanthra-cenes or from tetrabromopent-acenes using substituted and unsubstituted Sn,Sn-dimethylstan-nafluorenes, and employing Stille-type Pd-catalysis. [4] For the azaheptacenes[5] the necessary precursor is Müllen’s tetraamino-anthracene,[6 ] which is simply coupled to a suitably substituted phenanthrene-dione to give the butterfly-protected tetraazaacene in one convenient step.

Further developments in the chemistry of larger azaacenes in-clude their topologically diverse

32 assembly into linear, cyclic, and 3D-33 type objects, which have fascinating structural, electronic and potentially useful properties as OLED-34 emitters, for singlet splitting but also as potent non-fullerene electron acceptors in organic 35 photovoltaic cells. 36

37 References

38 [1] (a) U. H. F. Bunz, J. U. Engelhart, B. D. Lindner, M. Schaffroth, Angew. Chem. 52, 3810-3821 (2013). (b) U. H. 39 F. Bunz, Acc. Chem. Res. 48, 1676 (2015).

40 [2] H. Reiss, L. Ji, J. Han, S. Koser, O. Tverskoy, J. Freudenberg, F. Hinkel, M. Moos, A. Friedrich, I. Krummen-41 acher, C. Lambert, H. Braunschweig, A. Dreuw, T. Marder, U. H. F. Bunz, Angew. Chem. 57, 9543 (2018).

42 [3] E. C. Rüdiger, M. Müller, S. Koser, F. Rominger, J. Freudenberg, U. H. F. Bunz, Chem. Eur. J. 24, 1036 (2018).

43 [4]M. Müller, E. Rüdiger, S. Koser, O. Tverskoy, F. Rominger, F. Hinkel, J. Freudenberg, U. H. F. Bunz, Chem. Eur.

44 J. 24, 8087 (2018).

45 [5] M. Müller, H. Reiss, O. Tverskoy, F. Rominger, J. Freudenberg, U. H. F. Bunz Chem. Eur. J. 24, 12801 (2018).

46 [6] D. B. Xia, X. Guo, L. Chen, M. Baumgarten, A. Keerthi, K. Müllen, Angew. Chem. 55, 941 (2016).

47

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Molecular understanding of organic-organic interfaces and mixtures

Denis Andrienko

Max Planck Insttute for Polymer Research, Ackermannweg 10 Mainz 55128, Germany

We show how inclusion of mesoscale order (Figure 1) resolves the controversy between

experimental and theoretcal results for the energy-level profle and alignment in a variety of

photovoltaic systems, with direct experimental validaton [1,2]. We explain how this order and

interfacial roughness generate electrostatc forces that drive charge separaton and prevent carrier

trapping across a donor-acceptor interface [2]. Comparing several of small-molecule donor-fullerene

combinatons, we illustrate how tuning of molecular orientaton and interfacial mixing leads to a

trade-of between photovoltaic gap and charge-splitng and detrapping forces, with consequences

for the design of efcient photovoltaic devices. By accountng for long-range mesoscale felds, we

obtain the ionizaton energies in both crystalline [3] and mesoscopically amorphous systems with

high accuracy [4].

mesoscale

ord

er

acceptor donor

Figure: Disorder at the donor-acceptor interface and its impact on the electrostatc driving force.

References

[1] C. Poelking, M. Tietze, C. Elschner, S. Olthof, D. Hertel, B. Baumeier, F. Wuerthner, K. Meerholz, K.

Leo, D. Andrienko, Nature Materials, 14, 434, 2015

[2] C. Poelking, D. Andrienko, J. Am. Chem. Soc., 137, 6320, 2015

[3] M. Schwarze, W. Tress, B. Beyer, F. Gao, R. Scholz, C. Poelking, K. Ortstein, A. A. Guenther, D.

Kasemann, D. Andrienko, K. Leo, Science, 352, 1446, 2016

[4] C. Poelking, D. Andrienko J. Chem. Theory Comput., 12, 4516, 2016

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R R

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~s--V

Acenes and Extended Heterocyclic Quinodimethanes

Chunyan Chi

Department of Chemistry, National University of Singapore, Singapore

Acene-based molecular materials have been demonstrated to be useful semiconductors and chromophores. For example, pentacene and rubrene are among the top most studied molecules used in active layer in organic field effect transistors (OFETs) with high hole mobilities. Longer acenes can be also used as model compounds to investigate zig-zag edges of graphene. However, one drawback which hampers their general applications is their intrinsic instability. Typical reactions of acenes related to the diene conjugation include addition with singlet oxygen to form endoperoxide and dimerization under light irradiation. In addition, parent acenes usually have poor solubility in common organic solvents. Therefore, we have developed several strategies to stabilize and solubilize acene based molecules, and a few kinds of acene derivatives have been prepared. They include n-type acenes, cyclopenta- fused higher order acenes and acene dimers as well as quinoidal heteroacenes[1-7]. Heteroatom-containing quinoidal acene analogues and their charged forms could serve as good model compounds to understand the electronic properties of the all-carbon acenes. Some examples are shown below.

Figure 1. The chemical structures of some acene analogues and extended heterocyclic

quinodimethanes.

References [1] S. Dong, T. Y. Gopalakrishna, Y. Han, H. Phan, T. Tao, Y. Ni, G. Liu, C. Chi*, J. Am. Chem. Soc. 140, DOI:10.1021/jacs.8b10279. (2019). [2] Q. Jiang, T. Tao, H. Phan, Y. Han, T. Y. Gopalakrishna, T. S. Herng, G. Li, L. Yuan, J. Ding, C. Chi*, Angew. Chem. Int. Ed. 57, 16737-16741. (2018). [3] L. Yuan, Y. Han, T. Tao, H. Phan, C. Chi*, Angew. Chem. Int. Ed. 57, 9023-9027. (2018). [4] Q. Wang, T. Y. Gopalakrishna, H. Phan, T. S. Herng, S. Dong, J. Ding, C. Chi*, Angew. Chem. Int. Ed. 56, 11415-11419. (2017). [5] S. Dong, T. S. Herng, T. Y. Gopalakrishna, H. Phan, Z. L. Lim, P. Hu, R. D. Webster, J. Ding, C. Chi*, Angew. Chem. Int. Ed. 55, 9316-9320. (2016). [6] G. Dai, J. Chang, J. Luo, S. Dong, N. Aratani, B. Zheng, K.-W. Huang, H. Yamada, C. Chi*, Angew.

Chem. Int. Ed. 55, 2693-2696. (2016). [7] X. Shi, W. Kueh, B. Zheng, K.-W. Huang, C. Chi*, Angew. Chem. Int. Ed. 54, 14412-14416. (2015).

Predictive Modelling of Charge Transport in Organic Semiconductors

Naresh Kotadiya, Gert-Jan Wetzelaer, Anirban Mondal, Denis Andrienko, Paul W.M. Blom

Max Planck Institute for Polymer Research, Ackermannweg 10, Mainz, Germany

Charge transport is an important issue with regard to the understanding and optimization of

electronic devices made from organic semiconductors. Conjugated polymers and amorphous

small-molecule hole-transporting materials are commonly used in organic light-emitting diodes.

Characterization of their main functionality, hole transport and electron transport, has been

complicated by the presence of large contact barriers and trapping effects. Using a recently

developed technique to establish Ohmic hole contacts, we investigate the bulk hole transport

in a series of organic semiconductors with a broad range of ionization energies. The measured

charge-carrier mobility dependence on charge concentration, electric field, and temperature is

used to extract the energetic disorder and molecular site spacing. Excellent agreement of these

parameters as well as ionization energies with simulation results paves the way to predictive

charge-transport simulations from the molecular level.

10

20

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50

1 Color-Specific Photoswitching in Dual Color Fluorescent System 2 3 Soo Young Park, Dojin Kim, Ji Eon Kwon 4 5 Department of Materials Science and Engineering, Seoul National University, Seoul (Korea) 6 7 Fluorescence photoswitching system, which can turn on/off fluorescence by light irradiation, is 8 attracting much attention because of its potential in various optoelectronic applications including 9 optical memory, bioimaging, and super-resolution microscopy. In particular, a dual-color fluorescent

photoswitching system holds an additional opportunity due to its capability of ratiometric imaging, 11 which can reduce background cell autofluorescence in bioimaging field, and of multistate switching, 12 which can enable multi-distinguishable emission signals upon a single wavelength excitation. 13 However, dual-color fluorescence photoswtiching is very complicated because it demands elaborate 14 manipulation of intermolecular energy transfers (ET) between fluorophores and photoswitchable 15 chromophores. Two different modes of dual-color fluorescence photoswitching are color-correlated 16 switching and color-specific photoswitching. [1] While the former has been extensively investigated 17 and utilized for various applications, the latter has rarely been explored only with a few papers 18 demonstrating limited success. The essential challenge in the latter case is the total frustration of ET 19 between two emitters. In this presentation, we report innovative strategies to achieve dual-color

photoswitchable systems. The first is the rationally designed color-specific photoswitching system 21 composed of two excited-state intramolecular proton transfer (ESIPT) fluorophores and a color-22 specific photoswitchable diarylethene.[2] Based on its unique photophysical properties, this system 23 demonstrates an entirely new principle of color-specific photoswitching, which includes the 24 frustration of ET between two fluorophores and the selective ET from only one specific fluorophore 25 to the photochromic switch. The second is the two component system comprising the turn-on type 26 fluorescent diarylethene and one ESIPT dye.[3] This system is far excellent compared to the first 27 system in terms of the fluorescence on/off ratio and non-destructive read-out capability. We 28 synthesized water-soluble and biocompatible nanoparticle containing the two components to make 29 fluorescence imaging for bio-system and also to demonstrate the super-resolution microscopic

imaging. 31 32 References 33 [1] D. Kim, S. Y. Park, "Multi-Color Fluorescence Photoswitching: Color-Correlated vs. Color-Specific 34 Switching", Adv. Opt. Mater., 6, 1800678 (2018) 35 [2] D. Kim, J. E. Kwon, and S. Y. Park, "Is Color-Specific Photoswitching in Dual-Color Fluorescence 36 System Possible? Manipulating Intermolecular Energy Transfer among Two Different Fluorophores 37 and One Photoswitch", Adv. Opt. Mater., 4 (5), 790 (2016) 38 [3] D. Kim, J. E. Kwon, and S. Y, Park, Korea Patent, 10-1872922-00-00 (2018) 39

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Semiconducting Polymers for High Performance OFET and OECT Applications

Iain McCulloch

King Abdullah University of Science and Technology, KAUST Solar Center, Thuwal, (Kingdom of Saudi

Arabia)

The evolution of organic electronics has now reached the commercial phase, with the recent market introduction of the first prototypes based on organic transistors and organic solar cell modules fabricated from solution. Understanding the impact of both the organic semiconductor design and processing conditions, on both molecular conformation and thin film microstructure has been demonstrated to be essential in achieving the required optical and electrical properties to enable these devices. Polymeric semiconductors offer an attractive combination in terms of appropriate solution rheology for printing processes, mechanical flexibility for rollable processing and applications, but their optical and electrical performance requires further improvement in order to fulfil their potential. Synthesis of conjugated aromatic polymers typically involves carbon coupling polymerisations utilising transition metal catalysts and metal containing monomers. This polymerisation chemistry creates polymers where the aromatic repeat units are linked by single carbon-carbon bonds along the backbone. In order to reduce potential conformational, and subsequently energetic, disorder due to rotation around these single bonds, an aldol condensation reaction was explored, in which a bisisatin monomer reacts with a bisoxindole monomer to create an isoindigo repeat unit that is fully fused along the polymer backbone. This aldol polymerization requires neither metal containing monomers or transition-metal catalysts, opening up new synthetic possibilities for conjugated aromatic polymer design, particularly where both monomers are electron deficient. Polymers with very large electron affinities can be synthesised by this method, resulting in air stable electron transport, demonstrated in solution processed organic thin film transistors. We present an electrical, optical and morphology characterisation of polymer thin films, illustrating structure-property relationships for this new class of polymers. Organic electrochemical transistors (OECTs) have been shown to be promising devices for amplification of electrical signals and selective sensing of ions and biologically important molecules in an aqueous environment, and thus have potential to be utilised in bioelectronic applications. The sensitivity, selectivity and intensity of the response of this device is determined by the organic semiconducting polymer employed as the active layer. This work presents the design of new organic semiconducting materials which demonstrate significant improvements in OECT performance, through operation in accumulation mode, with high transconductance and low operating voltage. .

Room Temperature Phosphorescence

Ben Zhong Tang*

Department of Chemistry, The Hong Kong University of Science & Technology, Clear Water Bay, Kowloon,

Hong Kong, China

Center for Aggregation-Induced Emission, State Key Laboratory of Luminescent Materials and Devices,

South China University of Technology, Guangzhou, China

tangbenz@ust.hk

Materials with phosphorescence have attracted much attention from both scientists and engineers

owning to their potential applications in electronics, optics and biological area. So far, most of the

phosphorescent luminogens are inorganic and organometallic compounds, which suffer from poor

stability, high cost and rigidity, brittleness, difficulty in large-area processing and limited applications.

Organic materials, on the other hand, enjoy the advantages of wide variety, good biocompatibility,

appreciable stability and good processability. However, they only exhibit phosphoresce at low

temperature and in the absence of oxygen, owning to the high sensitivity and the long lifetimes of their

triplet excitons. In 2010, we discovered a novel phenomenon of crystallization-induced

phosphorescence (CIP) in benzophenone and its derivatives at room temperature.1 Despite the exciting

breakthrough of preparing pure organic materials with RTP properties, the development of efficient

pure organic RTP systems is still challenging and in the early stage. There is still no applicable guideline

for their molecular design, which awaits us to investigate and utilize. Here, we explored organic

chromophoric systems possessing efficient phosphorescence at ambient conditions.2-4

Figure 1. White light emission from single molecular with room temperature phosphorescence.3

References

1. Yuan, W. Z. B. Z. Tang et al. J. Phys. Chem. C. 2010, 114, 6090-6099.

2. W. Zhao, Z. He, B. Z. Tang et al. Chem, 2016, 1, 592-602.

3. Z. He, W. Zhao, B. Z. Tang et al. Nat. Commun. 2017, 8, 416

4. Y. Xiong, B. Z. Tang et al. Angew. Chem. Int. Ed. 2018, 57, 7997-8001.

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Ultrafast Properties of a Self-Doped Conjugated Polyelectrolyte

Demetra Tsokkou1, David Xi Cao2, Guillermo C. Bazan2, Thuc-Quyen Nguyen2, Natalie Banerji1

1University of Bern, Department of Chemistry and Biochemistry, 3012 Bern, Switzerland 2University of California at Santa Barbara, CEPOS, Santa Barbara, CA 93106, USA

The ultrafast optical processes in a self-doped conjugated polyelectrolyte, where any complications

related to dopant diffusion, formation of partial charge transfer complexes or structural disruption by

external dopant molecules are absent, are presented. Conjugated polyelectrolytes have conjugated

backbones with ionic side chains. Their numerous applications include biosensing, cell imaging and

interlayers in electronic devices. The ability to conduct both electronic and ionic charge, as well as

their favorable doping, make conjugated polyelectrolytes particularly interesting. CPE-K is a narrow-

bandgap conjugated polyelectrolyte, which was shown to become self-doped upon dialysis

treatment. The doping is directly evident in the absorption spectrum, where the P2 polaron band

appears around 1200 nm. By carefully determining the extinction coefficient of this band, we

estimate the doping density in the polyelectrolyte doped at different levels. We carried out transient

absorption (TA) spectroscopy in CPE-K solutions and thin films, with pumping in either the neutral S0-

S1 or the polaronic P2 transition. We show that there is electronic coupling of polarons to nearby

neutral sites, which share the same ground state for their optical transitions (both are depleted in

the TA experiments, no matter which transition is excited). Similar, correlated and very short-lived

dynamics are observed at both excitation wavelengths. This result contrasts with the conventional

picture of localized intragap polaron states and warrants a revised model for the electronic structure

and optical transitions in doped organic systems. We also show that inter-site Coulomb interactions

are present (i.e. the positive polarons cause a Stark shift in the transitions of nearby neutral sites).

The electronic coupling and electrostatic effects of the polarons occur independently on doping

concentration and on whether the self-doped material forms a thin film or is in solution. Finally, we

present the terahertz (THz) conductivity of those doped thin films, establishing the local carrier

mobility.

Functional π-Electron Systems14th International Symposium on

Abstracts Poster Presentation

Contributed Lectures

Monday, June 3rd

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1 Highly Efficient Thermally Activated Delayed Fluorescence (TADF) Emission Based on

2 Multi-π-Systems

3

4 Hong-Cheng Li,1

Lin-Song Cui,2

Xun Tang,1

Liang-Sheng Liao,1

Richard H. Friend,2

Zuo-Quan Jiang1

5

6 1Institute of Functional Nano & Soft Materials (FUNSOM), Soochow University, Suzhou (China)

7 2Cavendish Laboratory, University of Cambridge, Cambridge (UK)

8

9 Thermally activated delayed fluorescence (TADF) emitters have attracted considerable attention as

10 the third-generation organic light emitting diodes (OLEDs) materials because of their high

11 electroluminescent (EL) efficiency and the absence of rare metals such as iridium and platinum. Their

12 molecular design greatly depends on the Donor–π–Acceptor (D-π-A) type structure, in this way, the

13 highest occupied and lowest unoccupied molecular orbitals (HOMOs and LUMOs) can be decoupled

14 and the exchange integral between them can be minimized. Resultantly, a sufficiently small singlet–

15 triplet energy gap (ΔEST) can be achievable to make the materials fully harvest the singlet and the up-

16 converted triplet excitons for light emission.

17 After years of efforts, now the D–π–A molecular system is successful in designing highly efficient

18 TADF emitters with several examples exceeding 30% external quantum efficiency (EQE). The chief

19 mechanism of twisted induced charge transfer (TICT) for this system is also widely accepted. Despite

20 prosperous development on D–π–A TADF molecules, the infrastructural studies on other CT emissive

21 paradigms, such as D/A exciplex (intermolecular CT) or unconjugated D/A molecules (intramolecular

22 CT), never stop. Unlike conjugated D–π–A system, the HOMO and LUMO are thoroughly separated at

23 the ground state because of unconjugated D/A system. The absence of virtual conjugated linkage

24 within donor and acceptor also makes the TICT mechanism no longer applicable.

25 Herein, we designed and developed effective TADF materials by manipulating multi-π-systems. As a

26 simple result, our new strategy has novel mechanism to complete ICT process. And the related

27 material all exhibit obvious TADF feature with small ΔEST that can remarkably facilitate reverse

28 intersystem crossing (RISC) process. Along with the high photoluminescence quantum yield around

29 90%, good device performance can be expected, which is underway.

30

31 32 Figure 1. Steady photoluminescence properties

33

34 Reference:

35 [1] Y.-K. Wang, S.-H. Li, S.-F. Wu, C.-C. Huang, S. Kumar, Z.-Q. Jiang, M.-K. Fung, L.-S. Liao, Adv. Funct.

36 Mater. 28, 1706228 (2018).

37 [2] Y.-K. Wang, S.-F. Wu, Y. Yuan, S.-H. Li, M.-K. Fung, L.-S. Liao, Z.-Q. Jiang, Org. Lett. 19, 3155 (2017).

38 [3] Y. Yuan, Y. Hu, Y.-X. Zhang, J.-D. Lin, Y.-K. Wang, Z.-Q. Jiang, L.-S. Liao, S.-T. Lee, Adv. Funct. Mater.

39 27, 1700986 (2017).

Triphenylen (nicht kr. II.)

1 Discotic Liquid Crystals Do NOT Require Tails

2 3 Robert J. Twieg1, Zhe Li1, Kunlun Wang1, Parikshit Guragain1, Scott Bunge1

4 Dena Agra-Koojiman2, Mitchell Powers3, Lewis Sharpnack3, Brett Ellman3, Satyendra Kumar4

5 6 1Kent State University, Department of Chemistry and Biochemistry, Kent, Ohio, USA

7 2Kent State University, Advanced Materials and Liquid Crystal Institute, Kent, Ohio, USA

8 3 Kent State University, Department of Physics, Kent, Ohio, USA

9 4 SUNY Albany, Department of Physics, Albany, New York, USA

10 11 Nearly a century ago Vorländer had the remarkable insight to anticipate mesogenic activity in simple

12 disk-like polynuclear aromatic substances like triphenylene but he found no examples and none have

13 been described since then.[1] Later, Chandrasekhar demonstrated that the addition of multiple

14 flexible tails to even a simple benzene core induced discotic behavior.[2] During the intervening time

15 many thousands of discotic substances with multiple tails have been described and lore has evolved

16 that tails are required to deliver discotic behavior (in spite of evidence otherwise).[3] Well, after all,

17 Vorländer was right and simple triphenylene discotics sans tails do, in fact, exist. In the course of our

18 studies of fluorinated polynuclear aromatics as organic semiconductors synthesized via

19 photocyclodehydrofluorination (PCDHF) we have discovered a remarkable set of triphenylenes

20 bearing small substituents that possess discotic behavior.[4] The materials studied thus far have

21 halogen content (usually fluorine) and sometimes one or more additional small substituents (nitrile,

22 trifluoromethyl, etc., although such substituents are not mandatory). A challenge is to understand

23 the origins of the mesogenic behavior of these systems. Details of the synthesis methodology critical

24 for the preparation of these no-tail discotic materials, their mesomorphic properties and a

25 preliminary evaluation of charge transport in these tail free systems will all be presented. As discotic

26 liquid crystals have already played a significant role in the development and understanding of organic

27 semiconductors, it is anticipated that these new tail free systems will play an important role.

28 Evidence is accumulating that the design principles studied here on triphenylene will also apply to

29 still larger discotic aromatic polynuclear systems and are also relevant to crystalline materials as well.

a) b)

R

F4

R=H; not discotic

R=CF3, F, others; discotic

c)

R=CF3

d)

R=CF3

30 Fig. a) Vorlander’s insight. [1] b) Substituent dependent phase behavior: R=H K 205 I 193 K; R=CF3 K

31 167 D 176 I 174 D 115 K; R=F K 190 D 204 I 202 D 199 K’ 181 K. c) XRD of R=CF3 D phase at 176°C, d)

32 POM texture of R=CF3 D phase at 135°C.

33 [1] D. Vorländer, Chemische Kristallographie der Flüssigkeiten; Akademische Verlagsgesellschaft:

34 Leipzig (1924).

35 [2] S. Chandrasekhar, B. K. Sadashiva, K. A. Suresh, Pramana, 9, 471 (1977).

36 [3] S. Basurto, S. García, A. G. Neo, T. Torroba, C. F. Marcos, D. Miguel, J. Barberá, M. B. Ros, M. R. de

37 la Fuente, Chem. Eur. J., 11, 5362 (2005).

38 [4] Z. Li, R. J. Twieg, Chem. Eur. J., 21, 15534 (2015).

Optimization of donors and acceptors for organic photovoltaics guided by molecular

simulations

Micaela Matta,1,2 Steven M. Swick,1 Thomas J. Aldrich,1 Kevin L. Kohlstedt,1 Ferdinand Melkonian,1

Antonio Facchetti,1 Tobin J. Marks,1 George C. Schatz1

1Department of Chemistry, Northwestern University, Evanston (United States) 2Department of Chemistry, University of Liverpool, Liverpool (United Kingdom)

Organic bulk-heterojunction (BHJ) solar cells made of polymeric donors and small molecule non-

fullerene acceptors (NFA) have been the subject of interest due to their record-high efficiencies.[1]

Tremendous effort is being directed at the development of novel donor and acceptor building blocks,

and the optimization of energetics and morphology of donor/acceptor systems. In this work, we

demonstrate how computational insight from both ab initio ad molecular dynamics can be used to

guide the optimization of both donor and acceptors.

The polymer donor PBTZF4 was characterized using a combination of molecular dynamics (MD)

simulations, X-ray scattering and spectroscopic techniques. MD provided a rationalization for the

observed trends among a series of PBTZF4-R devices with alkyl chains R of different length,

elucidating the subtle equilibrium between the conjugated backbone rigidity and the folding

enhancement provided by longer alkyl chain substituents. The results established a relationship

between the single polymer chain behavior, its aggregation in solution and the subsequent formation

of domains in the BHJ.[2] This study shows how side chain engineering can be used to fine tune the

BHJ morphology without significantly changing the HOMO-LUMO levels of the polymer backbone.

We also performed a systematic investigation of a series of novel ITIC-derived acceptors. We used

both electronic structure methods and molecular dynamics simulations to investigate how changes in

the acceptor molecular structure influence both electronic properties (i.e., the reorganization

energy) and molecular packing, correlating them to their photovoltaic efficiency. In particular, the

effects of fluorination [3] and end-group conjugation extension[4] were studied.

Finally, a series of ITIC-derived[1] NFAs having alkyl chain substituents of different length[5] was also

investigated by means of quantum chemical calculations, MD simulations, X-Ray diffraction and other

spectroscopic measurements. It emerges that the alkyl chain length has a dramatic effect on OPV

performances. Side chains effectively mediate intermolecular interactions by preventing excessive

aggregation and crystallization of the acceptor while allowing efficient π-stacking in the amorphous

and semi-crystalline domains.

[1] J. Hou, O. Inganäs, R. H. Friend, and F. Ga, Nat. Mater. 17, 119-128 (2018).

[2] G. Wang, S. M. Swick, M. Matta, J. L. Logsdon, S. Fabiano, W. Huang, T. J. Aldrich, T. Yang, A.

Timalsina, N. Powers-Riggs, J. Alzola, R. M. Young, M. R. Wasielewski, K. L. Kohlstedt, G. C. Schatz, F.

S. Melkonyan, A. Facchetti, and T. J. Marks, in preparation.

[3] T. J. Aldrich, M. Matta, W. Zhu, S. M. Swick, C. Stern, G. C. Schatz, A. Facchetti, F. S. Melkonyan,

and T. J. Marks, J. Amer. Chem. Soc., submitted.

[4] S. M. Swick, W. Zhu, M. Matta, T. J. Aldrich, A. Harbuzaru, J. T. Lopez Navarrete, R. Ponce Ortiz, K.

L. Kohlstedt, G. C. Schatz, A. Facchetti, F. S. Melkonyan, and T. J. Marks, Proc. Natl. Acad. Sci. U. S. A.

115, E8341-E8348 (2018).

[5] M. Matta, W. Zhu, S. M. Swick, T. J. Aldrich, T. J. Marks, and G. C. Schatz, in preparation.

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Exciplex-forming systems for efficient organic light-emitting diodes

-mandatory blank line-Juozas V. Grazuleviciusa, Galyna Sycha, Oleksandr Bezvikonnyia, Dmytro Volyniuka, Ausra Tomkevicienea, Gintare Grybauskaite-Kaminskiene,a Khrystyna Ivaniuk b, Pavlo Stakhirab

-mandatory blank line-aDepartment of Polymer Chemistry and Technology, Kaunas University of Technology, Radvilenu rd.

19, LT-50254, Kaunas, Lithuania. Email: juozas.grazulevicius@ktu.lt bLviv Polytechnic National University, S. Bandera 12, 79013 Lviv, Ukraine.

-mandatory blank line-Organic exciplex-based systems that display thermally activated delayed fluorescence (TADF) are widely used in organic light-emitting diodes (OLEDs) [1]. Since electrons and holes are positioned on two different molecules, in exciplex-based systems small singlet-triplet splitting (ΔEST~0−0.03 eV) can be realized much easier than in case of single TADF molecules. TADF contribution in exciplex-based OLEDs can be maximized and theoretical internal quantum efficiency of 100% can be achieved [1]. In this presentation, several approaches of application of exciplex-forming systems in high-efficiency OLEDs exhibiting TADF will be demonstrated. Interface exciplex host, was applied for optimization and enhancement of performance of non-doped OLEDs based on new emitters showing aggregation induced emission enhancement [2]. The color-tunable OLEDs with the minimal number of the functional layers were designed and fabricated [3]. The voltage-dependent green-blue electrofluorescence was observed due to unique physical properties of the new ambipolar fluorophore 3,6-di(4,4’-dimethoxydiphenylaminyl)-9-(1-naphthyl)carbazole. Electroluminescence spectra of the devices contained blue fluorescence band, strong interface exciplex emission bands with the emission maximum at ca. 540 nm, and voltage-dependent electroplex emission bands in the region of 550-650 nm [3]. OLEDs based on carbazole and tetraphenylethylene derivatives exhibiting emission from both excitons and exciplexes based on aggregation-induced emission enhancement were designed fabricated and charaterized [4]. Extremely efficient warm-white OLEDs with harmless for the human eyes electroluminescence spectra were obtained [5]. In these OLEDs, sky-blue TADF of a carbazole derivative was combined with the yellow-orange exciplex emission of the derivative of bicarbazole and benzonitrile and a commercial donor. The best device demonstrated very high brightness of 40900 Cd/m2 (at 15 V), current efficiency of 53.8 Cd/A, power efficiency of 19.3 lm/W. Eexternal quantum efficiency of the device reached 18.8 %.

Acknowledgement

This research is/was funded by the European Social Fund according to the activity ‘Improvement of researchers’ qualification by implementing world-class R&D projects’ of Measure No. 09.3.3-LMT-K-712

References:

[1] M. Sarma and K.-T. Wong, ACS Appl. Mater. Interfaces, 2018, 10, 19279–19304. [2] G. Sych, J. Simokaitiene, O. Bezvikonnyi, U. Tsiko, D. Volyniuk, D. Gudeika and J. V. Grazulevicius, J. Phys.

Chem. C, 2018, 122, 14827–14837. [3] T. Deksnys, J. Simokaitiene, J. Keruckas, D. Volyniuk, O. Bezvikonnyi, V. Cherpak, P. Stakhira, K. Ivaniuk, I. Helzhynskyy, G. Baryshnikov, B. Minaev and J. V. Grazulevicius, New J. Chem., 2017, 41, 559–568. [4] D. Volyniuk, J. Sutaite, A. Tomkeviciene, N. Kostiv, G. Buika and J. V. Grazulevicius, J. Lumin., 2017, 192, 534– 540. [5] G. Grybauskaite-Kaminskiene, K. Ivaniuk, G. Bagdziunas, P. Turyk, P. Stakhira, G. Baryshnikov, D. Volyniuk, V. Cherpak, B. Minaev, Z. Hotra, H. Ågren and J.V. Grazulevicius J. Mater. Chem. C, 2018, 6, 1543-1550.

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' hv l Under u~v

= /2

Nonacene

hv l Under UHV

V,= - IV,1=4pA nc-AFM .

- _,,, f,r·-~

,S V, =-IV, I= 4 pA

nc-AFM I

df[Hz)

-2

~ 1~m ' •

On-surface light-induced synthesis of higher acenes from a-diketone-type precursors

1Hironobu Hayashi, 1Hiroko Yamada

1 Division of Materials Science/Nara Instituted of Science and Technology (NAIST), Nara (Japan)

Large aromatic molecules such as large acenes and polycyclic aromatic hydrocarbons are

regarded as promising materials for organic electronic devices. However, it is normally difficult to

synthesize such large aromatic molecules because of the low solubility and stability. On the other

hands, we have developed thermal and photochemical precursor methods to overcome these

problems. Briefly, bicyclo[2.2.2]octadiene(BCOD)-fused acenes can be converted to the corresponding

acenes by the thermally induced retro-Diels-Alder reaction, while a–diketone–type precursors can be

converted simply by photoirradiation [1]. Specifically, irradiation of a–diketone–type precursors at the

n-p* absorption leads to the release of two molecules of CO, and the corresponding acenes can be

prepared quantitatively in solutions or in films. Importantly, these precursor molecules are often more

soluble and stable than the corresponding one.

Here, we report the synthesis of a–

diketone–type dibromoheptacene

precursors. In addition, we also report the

on-surface formation of heptacene

organometallic complexes on Au(111) under

ultrahigh vacuum (UHV) conditions.

Scanning tunneling microscopy (STM) and

non-contact atomic force microscopy (nc-

AFM) revealed the formation of Au-

heptacene complexes via a selective two-

step activation of a-diketone-type

dibromoheptacene precursors [2]. Finally,

we demonstrate the on-surface synthesis of

heptacene and nonacene via visible-light-

induced photodecarbonylation on Au(111)

under UHV conditions. STM and nc-AFM

were used to investigate their chemical

structures (Fig. 1). Furthermore, scanning

tunneling spectroscopy (STS) measurements

experimentally reveal HOMO-LUMO gaps of

these large acenes [3]. These experimental

results together with theoretical calculations

indicate that acenes larger than hexacene

possess an increasing open shell character

on Au(111).

Reference

Figure 1. On-surface formation of heptacene and

nonacene on Au(111) under UHV conditions.

Acknowledgement: Dr. J. I. Urgel, and Prof. R.

Fasel@Empa.

[1] H. Yamada, Y, Yamashita, M. Kikuchi, H. Watanabe, T. Okujima, H. Uno, T. Ogawa, K. Ohara, N. Ono,

Chem.–Eur. J, 11, 6212 (2005).

[2] J. I. Urgel, H. Hayashi, M. D. Giovannantonio, C. A. Pignedoli, S. Mishra, O. Deniz, M. Yamashita, T.

Dienel, P. Ruffieux, H. Yamada, F. Roman, J. Am. Chem. Soc., 139, 11658 (2017).

[3] J. I. Urgel, S. Mishra, H. Hayashi, J. Wilhelm, C. A. Pignedoli, M. D. Giovannantonio, R. Widmer, M.

Yamashita, N. Hieda, P. Ruffieux, H. Yamada, F. Roman, Nat. Commun., in press (2019).

blend PCBM

Evac r o·-r •V LUMO

D A

0

[[">[ ,'<[ "' ~ CD

Organic-organic interface and energy of charge separation states in the film of donor and acceptor blends

Hiroyuki Yoshida1,2, Hiroyuki Ichikwa3, Ai Sugie3, Keiji Sando3, Itaru Osaka4

1Graduate School of Engineering, Chiba University, Chiba (Japan) 2Molecular Chirality Research Center, Chiba University, Chiba (Japan)

3Graduate School of Advanced Integration Science, Chiba University (Japan) 4Graduate School of Engineering, Hiroshima University, Higashi-Hiroshima (Japan)

Organic-organic interface plays a central role in the operation of such organic devices as organic solar cells (OCSs). The energy level alignment between the two organic materials at the interfaces has been extensively examined for the planer junctions; the HOMO and vacuum levels are measured as a function of the film thickness of the second material deposited on top of the first material using ultraviolet photoelectron spectroscopy (UPS). However, in the practical devices, the bulk-heterojunctions are usually employed where the thickness dependent experiments are no longer applicable. Instead of determining one-electron levels such as HOMO and LUMO levels, it is essential to discuss the total energy of each step because it is more rigorous and experimentally accessible. In OSC, for example, a blend film of donor and acceptor types of organic semiconductors are used where the exciton (Ex) generated by the photo-absorption is separated through the charge-transfer (CT) state at the donor/acceptor interface to the hole in the donor and the electron in the acceptor (charge-separation (CS) state) and the charges are collected (CC). While energies of the other states are determined by the optical transition or electrical measurements, the CS state energy has only roughly been estimated because the electron affinity of the acceptor cannot be measured precisely. Previously, we have demonstrated the low-energy inverse photoelectron spectroscopy (LEIPS) [1,2] can examine the LUMO levels with the precision similar to the HOMO levels using UPS. If the HOMO and LUMO of the blend films are contributed from the donor and acceptor, respectively, the CS state energy Ecs can be determined from the HOMO and LUMO energies of the blend film. In this work, we apply this procedure to the blend film of donor polymer, PNOz4T and acceptor molecule, PCBM used in the low energy loss OSC [3] in order to discuss the energy loss process in the OSC. The measured UPS and LEIPS spectra together with the energy level diagram are shown in Fig. 1. From he determined CS energy together with the energies of the other processes [3], it is found the CS energy is higher by 0.1-0.2 eV than the CT energy (Fig. 2). The same method was applied to an ordinary OCS and we found that difference in the energy loss between the ordinary and the low energy loss mainly occurs at the process from the exciton to the CT states.

donor (PNOz4T)

5.48

CS

blend Ex CT

5 37 3 72 CC

1.52 eV 1.53 eV 1.65 eV

0.97 eV 𝐸0

7 6 5 4 3 energy from Evac (eV)

2 Fig. 2: The state energies of low-energy

loss OCS (PNOz4T:PCBM [3]). Fig. 1: UPS-LEIPS spectra and energy diagram.

[1] H. Yoshida, Chem. Phys. Lett. 539-540, 180 (2012). [2] H. Yoshida, J. Electron Spectrosc. Relat. Phenom. 204, 116 (2015). [3] K. Kawashima, Y. Tamai, H. Ohkita, I. Osaka, K.Takimiya, Nature Comm. 6, 10085 (2015).

inte

nsity

(ar

b. u

nits

)

-mandatory blank line-

-mandatory blank line-

-mandatory blank line-

1.0

0.8

_, Q. 0.4

0.2

Thin film room temp PL CA T-1 pure drop-cast

0.0 +----~-.==-.------------1 700 750 800 850 900 950 1000

Wavelength (nm)

A design rule for obtaining efficient near-IR TADF emission beyond 1000 nm

Daniel G. Congrave, Bluebell H. Drummond, Dan Credgington, Hugo Bronstein

Department of Chemistry and Physics, University of Cambridge, United Kingdom

All-organic thermally activated delayed fluorescence (TADF) materials have emerged as next generation dopants in organic light emitting devices (OLEDs). Their emission has been widely tuned across the visible spectrum through modular synthesis, although they lag behind traditional fluorescent emitters in the near-IR region.[1] The longest wavelength TADF emitter reported to-date exhibits a λmax of ca. 800 nm,[2] while fluorescent emitters with λmax in excess of 1000 nm are well documented. Consequently, shifting their emission to comparably low energies is an immediate challenge.

TADF molecules are typically assembled from electron rich donor (D) and electron poor acceptor (A) heterocycles following the general formula Dn –A (n > 1), where an acceptor core is functionalised with numerous donor groups. Emission occurs from an intramolecular charge transfer (ICT) state. To obtain near-IR emission an exceptionally stabilised ICT state is required, which is achieved through ensuring the donor–acceptor interaction is as strong as possible. We reasoned that this requirement is compromised under the common Dn –A (n > 1) design strategy, as any improvement in donor strength afforded by incorporating multiple donors is mirrored by a weakening of the acceptor strength. This is evident from literature reports on red TADF materials,[3–5] where any red shift in emission afforded by additional donors is incremental at best compared to single donor–acceptor (D–A) dyad analogues.

We present the synthesis and photophysical study of two new D–A all-organic near-IR TADF emitters, CAT-1 and CAT-2. Removal of superfluous donor groups to obtain a D–A dyad structure liberates reactive positions on the acceptor unit for functionalisation with more beneficial electron withdrawing groups.[6] This simple design strategy enables TADF in excess of 1000 nm, and will be widely applicable to the development of future near-IR TADF materials.

[1] J. H. Kim, J. H. Yun, J. Y. Lee, Adv. Opt. Mater., 1800255. (2018). [2] H. Ye, D. H. Kim, X. Chen, A. D. S. Sandanayaka, J. U. Kim, E. Zaborova, G. Canard, Y. Tsuchiya,

E. Y. Choi, J. W. Wu, et al., Chem. Mater. 30, 6702–6710. (2018). [3] L. Yu, Z. Wu, G. Xie, W. Zeng, D. Ma, C. Yang, Chem. Sci. 9, 1385–1391. (2018). [4] H. Tanaka, K. Shizu, H. Nakanotani, C. Adachi, Chem. Mater. 25, 3766–3771. (2013). [5] X. Wei, L. Bu, X. Li, H. Ågren, Y. Xie, Dye. Pigment. 136, 480–487. (2017). [6] Y. K. Wang, S. F. Wu, S. H. Li, Y. Yuan, F. P. Wu, S. Kumar, Z. Q. Jiang, M. K. Fung, L. S. Liao, Adv.

Opt. Mater., 1700566. (2017).

' --~--,-~--

' '

/

/

1 A practical general method for the preparation of long acenes

2 -mandatory blank line-

3 Andrej Jancarik,1,2 Gaspard Levet,1 Andre Gourdon1

4 -mandatory blank line-

5 1CEMES-CNRS, Toulouse (France)

6 2Institute of Organic Chemistry and Biochemistry of the CAS, Prague (Czech Republic)

7 -mandatory blank line-

8 Acenes are planar polyaromatic hydrocarbons consisting of linearly fused benzene units and can be

9 considered as the narrowest zig-zag graphene nanoribbons. Acenes are very sensitive (mainly in

10 solution) but on the other hand very interesting organic compounds with unique electronic and

11 magnetic properties.1 Therefore, they have been predicted for use as molecular wires in single

12 molecule electronics, semi-conductors,2 for solar-cells applications,3 organic field-effect transistors,4

13 organic light emitting diodes etc. Although they have been known for decades and can be potentially

14 used in many applications, the absence of simple and practical synthesis hinders them to wider use.

15 The preparation in bulk of acenes beyond pentacene has been described only recently. Hexacene has

16 been prepared in 2012 by T.J. Chow et al.5 by cheletropic thermal decarbonylation of the carbonyl-

17 bridged precursor and heptacene by H.F. Bettinger et al. in 20176 by thermal cleavage of diheptacene

18 in the solid state, more than 70 years after the first attempted synthesis.

19 We developed new improved general methodology for preparation of acenes longer than

20 pentacene.7 The concept is based on the preparation of “carbon monoxide protected” precursors

21 formed by cycloaddition reaction between carbonyl-masked bis(diene) 1 and arynes. It is known that

22 CO bridged compounds 3 are stable and aromatize quantitatively upon heating under vacuum in the

23 solid state, or during sublimation. The generated compounds are pure enough to be used directly in

24 device fabrication.

-CO

A, B

A B

A B

OO

OO

A B

O

1 2

3425

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33 [1] J. P. Malrieu, G. Trinquier et al. J. Phys. Chem. A 120, 9564 (2016).

34 [2] C. Wang, H. Dong, Y. Liu, D. Zhu et al. Chem. Rev. 112, 2208 (2012).

35 [3] T. J. Carey, N. H. Damrauer et al. Org. Lett. 20, 457 (2018).

36 [4] N. A. Lakshminarayana, C. Chi et al. J. Mater. Chem. C 6 , 3551 (2018).

37 [5] M.Watanabe, T. J. Chow et al. Nat. Chem. 4, 574 (2012).

38 [6] R. Einholz, H. F. Bettinger et al. J. Am. Chem. Soc. 139, 4435 (2017).

39 [7] A. Jančařík, A. Gourdon et al. Chem. Eur. J. 10.1002/chem.201805975

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Embedded dipole SAMs for tuning electrode work functions -mandatory blank line-

Giulia Nascimbeni,1 Michael Gärtner,2 Eric Sauter,3 Andreas Petritz,4 Barbara Stadlober,4 Andreas Terfort,2 Michael Zharnikov,3 and Egbert Zojer1

-mandatory blank line-1Institute of Solid State Physics, Graz University of Technology, Graz (Austria)

2Institut für Anorganische und Analytische Chemie, Goethe-University Frankfurt, Frankfurt (Germany) 3Applied Physical Chemistry, Heidelberg University, Heidelberg (Germany)

4MATERIALS-Institute for Surface Technologies and Photonics, Joanneum Research, Weiz (Austria)

-mandatory blank line-The adsorption of polar self-assembled monolayers (SAMs) is a common strategy for modifying electrode work functions. Typically, the employed polar groups are attached as tail-group substituents, which has the disadvantage that they also influence the growth of organic semiconductor layers deposited on top of the SAM during the fabrication of organic electronic devices. To circumvent this problem, we developed conjugated SAM-forming molecules bearing polar elements (in particular pyrimidines[1]) embedded into their molecular backbones.[2,3] The resulting layers have been carefully characterized by a variety of surface-science techniques and their properties were explained using dispersion-corrected density-functional theory calculations. Varying the orientation of the embedded pyrimidines within the molecules allows changing the work function of the modified substrate by ± 0.5 eV compared to a reference nonpolar SAM. The underlying shift in the electrostatic energy at the position of the embedded pyrimidines can be clearly resolved by high-resolution x-ray photoelectron spectroscopy (XPS).[2,3] Employing monolayers consisting of mixtures of molecules with differently oriented polar groups also allows a continuous tuning of the system work function.[4] From the evolution of the electrostatic core-level shifts with the mixing ratio, one can conclude that the resulting films are highly homogeneous, which makes them promising for applications in optoelectronic devices. As the surface of the SAMs is essentially unaffected by the presence of the embedded polar groups, their presence does not modify the growth of organic semiconductor layers on the SAM-modified substrates.[5] Moreover, by properly tuning the length of the molecular backbones, the tunneling currents through the SAMs can be varied by an order of magnitude,[5] with high currents being crucial for the later application of the SAMs in electronic devices.

[1] D. A. Egger, F. Rissner, G. M. Rangger, O. T. Hofmann, L. Wittwer, G. Heimel, and E. Zojer, Phys.

Chem. Chem. Phys. 12, 4291 (2010). [2] T. Abu-Husein, S. Schuster, D. A. Egger, M. Kind, T. Santowski, A. Wiesner, R. Chiechi, E. Zojer, A. Terfort, and M. Zharnikov, Adv. Funct. Mater. 25, 3943 (2015). [3 M. Gärtner, E. Sauter, G. Nascimbeni, A. Petritz, A. Wiesner, M. Kind, T. Abu-Husein, M. Bolte, B. Stadlober, E. Zojer, A. Terfort, and M. Zharnikov, J. Phys. Chem. C 122, 28757 (2018). [4] I. Hehn, S. Schuster, T. Wächter, T. Abu-Husein, A. Terfort, M. Zharnikov, and E. Zojer, J. Phys.

Chem. Lett. 7, 2994 (2016). [5] A. Petritz, M. Krammer, E. Sauter, M. Gärtner, G. Nascimbeni, B. Schrode, A. Fian, H. Gold, A. Cojocaru, E. Karner-Petritz, R. Resel, A. Terfort, E. Zojer, M. Zharnikov, K. Zojer, and B. Stadlober, Adv.

Funct. Mater. 28, 1804462 (2018).

Stable para-Quinodimethane Derivatives for Optoelectronics

Quinoidal structures incorporating expanded para-quinodimethane (p-QM) units have garnered great interest as functional organic electronic, optical and magnetic materials. The direct use of the compact p-QM unit as an electronic building block, however, has been inhibited by the high reactivity associated with its biradical character. Herein, we introduce a stable p-QM variant, namely p-azaquinodimethane (p-AQM) that incorporates nitrogen atoms in the central ring and substituents on the periphery to tune the stability of the quinoidal structure.1 The p-AQM has many appealing features:

1. It can be synthesized via two simple steps with high regio- and stereospecificity from abundantly commercially available source. The thiophene-flanked p-AQMs feature a coplanar structure and rigid conformation with reduced rotational freedom due to intramolecular S•••N interactions.

2. It is the smallest analog of para-quinodimethane, which is stable without the need of ring expansion or installation of extra electron withdrawing groups.

3. The quinoidal characters of p-AQM endow distinctive electronic properties. It is not an electron acceptor based on its high LUMO energy level (~-2.9 eV). When incorporated in the polymer main chain as part of the resonating structure, however, it can effectively lower the polymer’s band gap via minimization of bond-length alternation to give very low band gap polymers reaching 1.3 eV.

4. The study of a series of copolymers employing varying numbers of thiophene units revealed an unconventional trend in band gaps, which is distinct from the widely adopted donor-acceptor approach to tuning the band gaps of conjugated polymers. Detailed theoretical calculations have shed light on the relationship between the band gaps and bond length alternation in the polymer main chains. Combined with side chain engineering, the resulting polymers show structure-dependent crystallinity in thin film devices with high hole transporting mobilities over 1 cm2V-1s-1.2

5. The chemistry is readily tunable, allowing the synthesis of ionic conjugated low bandgap polymers, as well as topochemical polymers.

References: 1. Liu, X.; He, B.; Anderson, C.; Kang, J.; Chen, T.; Chen, J.; Feng, S.; Zhang, L.;

Kolaczkowski, M.; Teat, S.; Brady, M.; Zhu, C.; Wang, L.; Chen, J.;* Liu, Y.* “para-Azaquinodimethane: a Compact Quinodimethane Variant as an Ambient Stable Building Block for High Performance Low Band Gap Polymers”, J. Am. Chem. Soc. 2017, 139, 8355-8363.

2. Liu, X.; He, B.; Ruiz, A. G.; Amparo, N.; Chen, T. L.; Kolaczkowski, M. A.; Feng, S.; Zhang, L.; Anderson, C. A.; Chen, J.*; Liu, Y.* “Unraveling the Main Chain and Side Chain Effects on Thin Film Morphology and Charge Transport in Quinoidal Conjugated Polymers”, Adv. Funct. Mater. 2018, 28, 1801874.

1 Engineering Thin Films of a Tetrabenzoporphyrin toward Efficient Charge-Carrier Transport

2

3 Hiroko Yamada1, Kohtaro Takahashi1, Eunjeong Jeong1, Tatsuya Ito1, Mitsuharu Suzuki2

4

5 1Graduate School of Science and Technology, Nara Institute of Science and Technology, Ikoma (Japan)

6 2Graduate School of Engineering, Osaka University, Suita (Japan)

7

8 Tetrabenzoporphyrin (BP) is a p-type organic semiconductor characterized by the large, rigid p-

9 framework, excellent stability, and good photoabsorption capability. These characteristics make BP

10 and its derivatives prominent active-layer components in organic electronic and optoelectronic devices.

11 However, the control of the solid-state arrangement of BP frameworks, especially in solution-

12 processed thin films, has not been intensively explored, and charge-carrier mobilities observed in BP-

13 based materials have stayed relatively low as compared to those in the best organic molecular

14 semiconductors. This work concentrates on engineering the solid-state packing of BP derivatives

15 toward achieving efficient charge-carrier transport in its solution-processed thin films.

16 First, we prepared a brickwork packing, that has two dimensionally extended p-staking, of 5,15-

17 bis(triisopropylsilylethyny)ltetrabenzoporphyrin (TIPS-BP) by optimizing deposition process, cast

18 solvent, and self-assembled monolayer that constitutes the dielectric surface. The calculated transfer

19 integral (t) for the brickwork motif was 40.0 and 22.2 meV and the dip-coated film showed the

V–1 20 maximum field-effect hole mobility (µh) of 1.1 cm2 s–1 [1]. For further improvement, 5,15-

21 bis(dimethyloctylsilylethynyl)-BP (C8DMS-BP) was synthesized by employing C8DMS groups instead of

22 TIPS substituent. The packing structure was changed from brickwork to herringbone motif with t of

23 79.0 meV and the optimized µh was 3.0 cm2 V–1 s–1 . The insertion of Cu2+ ion in the cavity of BP (C8DMS-

24 CuBP) further improved µh to 5.8 cm2 V–1 s–1 as maximum. The presentation will discuss the relationship

25 among molecular structure, molecular arrangement, and µh characteristics.

26

M = 2H, C8DMS-BP TIPS-BP

22.2 meV 4.1 meV

40.0 meV

Brickwork motif µh = 1.1 cm2 V-1 s-1

79.0 meV

6.8 meV

Herringbone motif C8DMS-BP µh = 3.0 cm2 V-1 s-1

C8DMS-CuBP µh = 5.8 cm2 V-1 s-1

M = Cu, C8DMS-CuBP

28 Fig. 1. Molecular structures, packing structures, calculated transfer integral (t) values and the

29 maximum field effect hole mobilities (µh) of TIPS-BP and C8DMS-BPs.

30

31 [1] K. Takahashi, B. Shan, X. Xu, S. Yang, T. Koganezawa, D. Kuzuhara, N. Aratani, M. Suzuki,* Q. Miao,*

32 and H. Yamada,* ACS Appl. Mater. Interfaces 9, 8211-8218. (2017).

27

33

Tailor-making π-extended optical force probes for stress sensing in materials

Robert Göstl1

1DWI – Leibniz Institute for Interactive Materials, Aachen (Germany)

Comparable to light, heat, or electrical current, mechanical stress is a physicochemical stimulus that can be used to alter the properties of small molecules and materials allowing access to latent functionality. We tailor-make small force-responsive molecules and integrate them into macromolecular architectures with the goal to harvest properties, such as mechanical self-reinforcement or the release of active moieties to perform chemical reactions, on a material level.[1] Besides this productive use, mechanical stress usually serves as a destructive element entailing the development of a wide range of macromolecular materials with outstanding mechanical properties. Using optical molecular force probes that turn “on” their fluorescence under mechanical load, we try to unravel the influences of structural elements in these, oftentimes complex, polymeric architectures.[2,3] For this purpose, we developed a molecular framework based on the force-induced retro Diels-Alder reaction of π-extended anthracenes and maleimide transforming these optically silent, latent force probes into highly sensitive fluorophores. This allows the localization of force scale-invariantly from the macroscopic down to the molecular level by using fluorescence spectroscopy and confocal laser scanning microscopy (CLSM). We parallelize stress sensing by simultaneously using optically complementary force probes emitting light in different regions of the visible spectrum (Figure 1). This helps us to better understand the mechanical properties of complex, non-heterogeneous materials and their interfaces. Moreover, we demonstrate anti-Stokes stress sensing by rendering triplet-triplet annihilation photon upconversion activatable by mechanical force. Eventually, we show that the combination of feedback and functionality is possible by mechanochemically generating persistent, colored radicals that initiate a self-reinforcing secondary network formation within a material.[4]

Figure 1 | Benzothiadiazole force probe (χ = 0.02 mol%) as mechanosensitive crosslinker in a cut PHMA network. a) Overlay of optical microscopy and CLSM of the activated mechanophore (λex = 476 nm). b) Only

optical microscopy. c) Fluorescence microscopy of inactive mechanophore (λex = 405 nm). d) Only CLSM of the

activated mechanophore (λex = 476 nm). e) Overlay of optical microscopy, CLSM of the activated

mechanophore (λex = 476 nm), and fluorescence microscopy of inactive mechanophore (λex = 405 nm).

[1] R. Göstl, J. M. Clough, and R. P. Sijbesma, in Mechanochemistry in Materials, Royal Society of Chemistry, 53–75 (2017).

[2] R. Göstl and R. P. Sijbesma, Chem. Sci., 7, 370–375 (2016). [3] H. Li, R. Göstl, M. Delgove, J. Sweeck, Q. Zhang, R. P. Sijbesma, and J. P. A. Heuts, ACS Macro

Lett., 5, 995–998 (2016). [4] F. Verstraeten, R. Göstl, and R. P. Sijbesma, Chem. Commun., 52, 8608–8611 (2016).

Stable enantiomers Tethered twistacenes Tunable torsion angle 50---------~

w O -~1";1t;:~ :\, <l !.X---------~ ~ ¢== t ~

400 450

1 Helically-Locked Tethered Twistacenes

2 3 Anjan Bedi and Ori Gidron* 4 5 *Institute of Chemistry, The Hebrew University of Jerusalem, Jerusalem, (Israel)

6 7 Acenes, which can be viewed as one-dimensional graphene nanoribbons, are an important class of 8 organic electronic materials. Twisting linear acenes out of planarity affects their electronic and 9 optical properties, and induces axial chirality. However, it is difficult to isolate the effect of twisting

10 from the varying substituents surrounding the acene core. Additionally, many twistacenes (twisted 11 acenes) readily racemize in solution.[1] We envisaged that the dynamic conformation flipping of 12 acene backbone could be locked by molecular tethering, such as was previously applied to achieve 13 bending in larger polyaromatic systems.[2]

14 Here we present a new series of twistacenes having an anthracene backbone diagonally tethered by 15 n-alkyl bridge of different lengths, which induce a backbone twist of various angles.[3] This allows us 16 to systematically monitor the effect of twisting on electronic, optical and chiroptical properties. We 17 find that absorption is bathochromically shifted with increasing twist, while fluorescence quantum 18 efficiency drops dramatically. Enantiomerically pure twistacenes display strong chiroptical properties 19 with no racemization even upon prolonged heating, rendering them as attractive candidates for 20 axially-chiral building units of π-conjugated backbones.[4]

21 22

23 24 Schematic representation of tethered twisted acenes (center). Arrows indicate increasing Cotton

25 effect in ECD spectra (left) and bathochromic shift in absorption spectra (right) upon increasing

26 anthracene twist.

27 28 29 References

30 [1] J. Lu, D. M. Ho, N. J. Vogelaar, C. M. Kraml and R. A. Pascal, J. Am. Chem. Soc. 126, 11168. (2004). 31 [2] P. R. Nandaluru, P. Dongare, C. M. Kraml, R. A. Pascal, L. N. Dawe, D. W. Thompson and G. J. 32 Bodwell, Chem. Commun. 48, 7747. (2012). 33 [3] A. Bedi, L. J. W. Shimon and O. Gidron, J. Am. Chem. Soc. 140, 8086. (2018). 34 [4] A. Bedi and O. Gidron, Chem. Eur. J. DOI:10.1002/chem.201805728. (2019).

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Controlling carrier type and contact resistances in organic thin-film transistors

Markus Krammer,1 James W. Borchert,2 Andreas Petritz,3 Esther Karner-Petritz,3 Gerburg Schider,3

Eric Sauter,4 Michael Gärtner,5 Michael Zharnikov,4 Andreas Terfort,5 Barbara Stadlober3, Hagen Klauk2 and Karin Zojer1

1Institute of Solid State Physics, NAWI Graz, Graz University of Technology, Graz (Austria) 2Max Planck Institute for Solid State Research, Stuttgart (Germany)

3Institute for Surface Technologies and Photonics, Joanneum Research Materials, Weiz (Austria) 4Applied Physical Chemistry, Heidelberg University, Heidelberg (Germany)

5Institut für Anorganische und Analytische Chemie, Goethe‐University,Frankfurt am Main (Germany)

For organic thin-film transistors (TFTs) it is often observed or predicted that top-contact devices outperform their bottom-contact counterparts. Yet, a comparison of device geometries and electric-field distributions suggests that bottom-contact TFTs have the potential for smaller contact resistances. [1] Until recently, this hypothesis had not been confirmed, mainly due to the difficulty of optimizing injection barriers and organic-semiconductor growth in bottom-contact organic TFTs. Recently, bottom-contact TFTs with Au source/drain contacts modified with pentafluorobenzenethiol have been realized that show a contact resistance of 29 Ohm-cm and indeed outperform top-contact TFTs for sufficiently thin gate dielectrics.[2]. To the best of our knowledge, this is the smallest contact resistance reported to date for bottom-gate organic TFTs. As an alternative approach, some of us have recently developed the concept of embedded dipole monolayers to tune the contact work function independent of the organic semiconductor growth.[3] These layers consist of polar molecules whose dipole orientation modifies the contact work function, and since the polar moieties are contained in the molecular backbones, the SAM-semiconductor interface and hence the semiconductor growth are not affected. Employing such SAMs in pentacene and C60-based bottom-contact TFTs, we have recently been able to tune the contact resistance by over three orders of magnitude and realize highly efficient p- and n-channel device operation employing the same contact metal (Au).[4] These results call for a method to accurately and reliably determine the contact resistance directly from the current-voltage characteristics of the TFTs, because traditional methods, such as the transmission-line method, are intrinsically flawed. To overcome the known limitations of these traditional contact-resistance-extraction methods, we suggest a two-step method that addresses two crucial aspects simultaneously: (1) the method extracts contact resistances and charge-carrier mobilities and distinguishes between Ohmic and non-Ohmic resistance contributions due to, e.g., injection barriers, and (2) this method allows, for the first time, to critically check whether the underlying theoretical model of the transistor operation is correct.[5]

[1] J. Brondijk, J. Torricelli, E.C.P Smits, P.W.M. Blom, D. Leeuw, Org. Electron. 13, 1526 (2012); M. Gruber, E. Zojer, F. Schürrer, K. Zojer, Adv. Funct. Mater. 23, 2941-2952 (2013). [2] J. W. Borchert, B. Peng, F. Letzkus, J. N. Burghartz, P. K. L. Chan, K. Zojer, S. Ludwigs, H. Klauk, under revision (2019). [3] T. Abu-Husein, S. Schuster, D. A. Egger, M. Kind, T. Santowski, A. Wiesner, R. Chiechi, E. Zojer, A. Terfort, and M. Zharnikov, Adv. Funct. Mater. 25, 3943 (2015) [4] A. Petritz, M. Krammer, E. Sauter, M. Gärtner, G. Nascimbeni, B. Schrode, A. Fian, H. Gold, A. Cojocaru, E. Karner‐Petritz, R. Resel, A. Terfort, E. Zojer, M. Zharnikov, K. Zojer, B. Stadlober, Adv. Funct. Mater. 28, 1804462 (2018). [5] M. Krammer, J. W. Borchert, A. Petritz, E. Karner-Petritz, G. Schider, B. Stadlober, H. Klauk, K. Zojer, Crystals 9, 85 (2019).

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Soft-chromophoric " Liquid" Porphyrin

"Stretchable Electret"

Alkylated-π Functional Molecular Liquids toward Stretchable Electret Applications

Takashi Nakanishi,1 Avijit Ghosh,1 Manabu Yoshida2

1International Center for Materials Nanoarchitectonics (WPI-MANA), National Institute for Materials

Science (NIMS), Tsukuba (JAPAN) 2Flexible Electronics Research Center (FLEC), National Institute of Advanced Industrial Science and

Technology (AIST), Tsukuba (Japan)

Newly developing functional soft materials, namely functional molecular liquids (FMLs), are recently

focused much attention toward the most promising candidate to be fabricated into

foldable/stretchable electronic devices. In particular, solvent-free alkylated-π liquids exhibit excellent deformability, photo-/thermal- stability and predictable π-unit based optoelectronic functions.[1-4]

Herein, we report unprecedented ‘liquid electret’ devices by using newly designed solvent-free liquid porphyrins which show

mechanoelectrical and electroacoustic functions

as well as their stretchable performance. Our

strategy of shielding π-unit of free-base

tetraphenylporphyrins with insulating flexible

and bulky-alkyl chains are suitable for stably

holding electric charges by the π-unit of liquid-

porphyrins. We believe, this intriguing liquid-

electret’s piezoelectric and electroacoustic device applications will uncover a new paradigm

for alkylated-π liquids in the developments of next generation wearable/stretchable

electronics toward healthcare applications.

of a liquid porphyrin, and stretchable liquid electret device and its mechanoelectric response.

References

[1] S. S. Babu, T. Nakanishi, et al., Nature Commun., 4, 1969 (2013).

[2] M. J. Hollamby, T. Nakanishi, et al., Nature Chem., 6, 690-696 (2014).

[3] F. Lu, T. Takaya, T. Nakanishi, et al., Sci. Rep., 7, 3416 (2017).

[4] F. Lu, T. Nakanishi, et al., Chem. Sci., 9, 6774-6778 (2018).

Fig. Schematic structural model and photograph

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---------o Q 0

"""K /,l I(_~

y

Bench-top, sustainable access to conjugated materials: how far you can go with tap water,

a stirring plate, very little palladium and a little soap.

Sara Mattiello, Alessandro Sanzone, Mauro Sassi, Chiara Ceriani, Adiel Mauro Calascibetta, Luca

Beverina.

Department of Materials Science, University of Milano-Bicocca, Milano (Italy)

Organic (opto)electronics has played a major role in academic and industrial research in the last 30

years, eventually reaching market maturity and holding promises for sizeable further growth. Very

few materials have been produced in industrially relevant scale, and the most performing ones are

not amongst them. Indeed, if on the lab scale the research is still very much focused on

performances, industrialization requires sustainable processes and reduction of pollutants and

hazards to a level compatible with large scale production. Mostly, organic materials are not water

soluble thus requiring the use of more or less flammable/toxic solvents for manufacturing and

handling. As a result, only highly efficient processes featuring high yield, small number of steps and

generally high concentration can satisfactorily go through the “lab to fab” evolutionary process.

Modern organic chemistry methods are increasingly relying on the use of water as the main reaction

medium, unregarding to the water solubility of reagents and products. The key components enabling

such reactions are specifically devised surfactants that, along with water and the water insoluble

reagents, lead to the formation of a range of interface rich systems the like of micellar solutions,

emulsions, microemulsions and dispersions. Provided that such microheterogeneous systems are

correctly handled, a wide variety of synthetically invaluable reactions like the Suzuki-Miyaura, Stille,

Buchwald-Hartwig, Heck, Neghisi, Sonogashira and many more becomes accessible at room

temperature, in water and sometimes even without any special precaution in keeping oxygen out of

the reaction environment.[1] In this contribution we will show how this kind of “benchtop” chemistry

enables the high yield preparation of notable small molecule organic semiconductors of the

diketopyrrolopyrrole, isoindigo, perylenediimides, benzothiadiazole and acenes families as well as

relevant polymers like F8BT and polyfluorene.[2,3] Relevant differences between such water based

over standard organic solvent promoted reactions will be highlighted.

SN N

S

S F F

C6H13 C12H25

S C10H21C10H21Room temperature S O N OC8H17

2 wt % surfactant

No protection from O2 N

O S S C6H135-600 ppm of Pd SC6H13 SO> 90 % yield

N

S C8H17 O N O C10H21 C10H21

S C12H25

C6H13

[1] S. Serrano-Luginbühl, K. Ruiz-Mirazo, R. Ostaszewski, F. Gallou, P. Walde Nat. Rev. Chem. 2, 306-

327. (2018)

[2] A. Sanzone, A. Calascibetta, E. Ghiglietti, C. Ceriani, G. Mattioli, S. Mattiello, M. Sassi, L. Beverina J.

Org. Chem. 83, 15029-15042. (2018)

[3] S. Mattiello, M. Rooney, A. Sanzone, P. Brazzo, M. Sassi, L. Beverina Org. Lett. 19, 654-657. (2017)

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2

Novel organic compounds for solution-processed thin film organic lasers

-mandatory blank line-

María A. Díaz-García1, Rafael Muñoz-Mármol

1, Víctor Bonal

1, Marta Morales-Vidal

1,

José M. Villalvilla1, Mariluz Martínez-Marco

1, Eva M. Calzado

2,

Carmen Vázquez3, Pedro G. Boj

3, José A. Quintana

3

1 Dept. Física Aplicada and IUMA, Universidad de Alicante, Alicante 03080, Spain 2 Dept. Física, Ing. sistemas y teoría señal and IUMA, Universidad de Alicante, Alicante 03080, Spain 3 Dept. Óptica, Farmacología y Anatomía, and IUMA, Universidad de Alicante, Alicante 03080, Spain

During the last years there has been extensive research towards the development of optically-

pumped solution processed thin film organic lasers, due to various advantages, such as chemical

versatility, wavelength tunability, mechanical flexibility and low cost. Probably the most successful

device has been the distributed feedback (DFB) laser, which so far has demonstrated its applicability

in various fields, such as spectroscopy, optical communications, biosensing and chemical sensing.

In this presentation we will discuss recent advances of our research group in the field, focusing

mainly on the use of novel compounds to be used as active laser media. They include

perylenediimide (PDI) dyes dispersed in thermoplastic polymer films [1,2], some of them at doping

rates as high as 50 wt%, being this value significantly larger than the typical ones used with standard

laser dyes (1 - 5 wt%). PDI-based lasers have been used as sensors of various kinds [3,4]. Results on

carbon-bridged oligophenylenevinylenes (COPVn, with n = 1 to 6), dispersed in thermoplastic

polymer films, emitting in a wide range of wavelengths within the visible spectrum at very low

thresholds and with excellent photostability, will be also described [5]. Also, on a novel COPV-

polymer prepared as a neat film with a significantly improved performance [6]. We will also discuss

progress on novel compounds of other families, which are presently being studied.

Additionally, we will describe a successful DFB architecture proposed recently by our group,

consisting on a solution-processed top-layer resonator fabricated by holographic lithography

deposited over an active film of uniform thickness [7]. The combination of this architecture with

good performing dyes has resulted in larger laser efficiencies and similar thresholds than the ones

obtained with resonators fabricated in inorganic substrates. In addition, this approach allows the

fabrication of color tunable devices within a single chip.

We acknowledge support from the Spanish Government (MINECO) and the European Community

(FEDER) through grant MAT2015-66586-R. R. M-M is supported by FPI contract BES-2016-077681.

[1] M.G. Ramírez, S. Pla, P.G. Boj, J.M. Villalvilla, J.A. Quintana, M. A. Díaz-García, F. Fernández-Lázaro

and A. Sastre-Santos, Adv. Optical Mater. 1, 933 (2013).

[2] R. Muñoz-Mármol, N. Zink-Lorre, J. M. Villalvilla, P. G. Boj, J. A. Quintana, C. Vázquez, A. Anderson,

M. J. Gordon, A. Sastre-Santos, F. Fernández-Lázaro and M. A. Díaz-García, J. Phys. Chem. C 122, 43,

24896 (2018).

[3] A. Retolaza, J. Martínez-Perdiguero, S. Merino, M. Morales-Vidal, P.G. Boj, J.A.Quintana, J.M.

Villalvilla and M.A. Díaz-García, Sens. Actuators B 223, 261 (2016).

[4] P. G. Boj, M. Morales-Vidal, J. M. Villalvilla, J. A. Quintana, A. Marcilla and M. A. Díaz-García, Sens. Actuators B 232, 605 (2016).

[5] M. Morales-Vidal, P. G. Boj, J. M. Villalvilla, J. A. Quintana, Q. Yan, Nai-Ti Lin, X. Zhu, N.

Ruangsupapichat, J. Casado, H. Tsuji, E. Nakamura, M. A. Díaz-García, Nat. Commun. 6, 8458 (2015).

[6] M. Morales-Vidal, J.A. Quintana, J.M. Villalvilla, P.G. Boj, H. Nishioka, H. Tsuji, E. Nakamura, G.L.

Whitworth, G.A. Turnbull, I.D.W. Samuel, M.A. Díaz-García, Adv. Optical Mater. 6, 1800069 (2018).

[7] J. A. Quintana, J. M. Villalvilla, M. Morales-Vidal, P. G. Boj, X. Zhu, N. Ruangsupapichat, H. Tsuji, E.

Nakamura and M. A. Díaz-García, Adv. Optical Mater. 5, 1700238 (2017).

Pressure

160 V ~ - IO V Vd ~ -60 V gs s ,,a ••••••••••• •• • ••

... ...... • s~32° KP _, 120 ,. i ..

'I'

••·• a

f 40 ; S~5!4 KPa- 1

f ; ~ 0"

0 500 1000 Pressure (Pa)

1500

1 Semiconductor/conductor interface piezoresistive effect for novel pressure sensor with 2 tunable sensitivity 3 -mandatory blank line-4 Zhongwu Wang, Liqiang Li 5 -mandatory blank line-6 Tianjin Key Laboratory of Molecular Optoelectronic Sciences, Department of Chemistry, Institute of 7 Molecular Aggregation Science, Tianjin University, Tianjin 300072, China 8 -mandatory blank line-9 Piezoresistive pressure sensor, a kind of widely-investigated artificial device to transfer force stimuli

10 to electrical signals, generally consists of one or more kinds of conducting materials. Here, a novel 11 highly sensitive pressure sensor based on semiconductor/conductor interface piezoresistive effect is 12 successfully demonstrated by using organic transistor geometry [1,2]. Because of the efficient 13 combination of piezoresistive effect and field-effect modulation in single sensor, this pressure sensor 14 shows multiple excellent performance such as high sensitivity (514 KPa-1), low limit of detection, 15 short response and recovery time and robust stability. More importantly, the unique gate 16 modulation effect in transistor endows the sensor an unparalleled ability—tunable sensitivity via bias 17 conditions in single sensor, which is of great significance for applications in complex pressure 18 environment. The novel working principle and high performance represent a significant progress in 19 the field of pressure sensors. 20

21 22 Figure 1. The schematic diagram of device structure of pressure sensor (upper panel) and the curve 23 of relative current change versus pressure showing the sensitivity (bottom panel) 24

25 [1] Zhongwu Wang, Shujing Guo, Hongwei Li, Bin Wang, Yongtao Sun, Zeyang Xu, Xiaosong Chen, 26 Kunjie Wu, Xiaotao Zhang, Feifei Xing, Liqiang Li*, and Wenping Hu, Adv. Mater. doi:adma201805630. 27 Published online.

28 [2] Hongwei Li, Kunjie Wu, Zeyang Xu, Zhongwu Wang, Yancheng Meng, and Liqiang Li*, Acs Appl. 29 Mater. Interface, 10, 20826-20834 (2018).

30 31 32

R

R = Alkyl

/ (NH4)2S20s FeCl3 f"'lrN>.--,_ ~ E=1.0V ~ E>1 .2V

~ E > 1.2 V

R

~ -,- ~ n

1 Electrochemical Synthesis of Functional Polymers

2 3 Mao Li,* Shusen Kang, Jian Zhang 4 5 State Key Laboratory of Polymer Physics and Chemistry, Changchun Institute of Applied Chemistry,

6 Chinese Academy of Sciences, Changchun (China)

7 8 9-substituted carbazoles were widely used units in materials science, and their oxidative reactions 9 have been utilizing for polymer synthesis and characterizations. Though the oxidative mechanism of

10 carbazoles was recognized very early for a few decades, the structural definition has been remaining 11 difficult because their polymers are generally insoluble with incomplete characterizations and 12 unknown dependence of electrochemical potentials. The oxidative reactions of 9-substituted 13 carbazoles should be carefully considered under the specific oxidative conditions, otherwise, the 14 structure definitions could be wrong because IR and NMR spectra used previously cannot 15 quantitatively analyze 3,3'-coupling and 6,6'-coupling of carbazoles. In this talk, I would present my 16 best understanding on C(3)-C(3') and C(6)-C(6') oxidative couplings of 9-substituend carbazoles that 17 what can be benefit from these oxidative reactions for synthesis and processes of topology and 18 sequence controlled functional polymers.

19 20 21 References

22 [1] J. Zhang, J. Du, J. Wang, Y. Wang, C. Wei, M. Li,* Angew. Chem. Int. Ed. DOI: 23 10.1002/anie.201809567. (2018) 24 [2] M. Li, S. Kang, J. Du, J. Zhang, J. Wang, K. Ariga, Angew. Chem. Int. Ed. 57, 4936 (2018). 25 [3] M. Li, Chem. Eur. J. DOI: 10.1002/anie.201809567. (2018) Review

26 [4] S. Kang, L. Wang, J. Zhang, J. Du, M. Li, Q. D. Chen, ACS App. Mater. Inter. 9, 32179 (2017). 27 [5] S. Kang, J. Zhang, L. Sang, L. K. Shrestha, M. Li, K. Ariga, ACS App. Mater. Inter. 8, 24295 (2016). 28 [6] Y. X. Gao, J. Qi, J. Zhang, S. Kang, W. Qiao, M. Li, K. Ariga, Chem. Commun. 50, 10448 (2014). 29 [7] M. Li, S. Ishihara, K. Ohkubo, M. Liao, Q. Ji, C. Gu, Y. Pan, X. Jiang, M. Akada, J. Hill, T. Nakanishi, Y. 30 Ma, Y. Yamauchi, S. Fukuzumi, K. Ariga, Small 9, 2064 (2013). 31 [8] M. Li, J. Zhang, H. J. Nie, M. Liao, L. Sang, W. Qiao, Z. Wang, Y. Ma, Y. Zhong, K. Ariga, Chem. 32 Commun. 49, 6879 (2013). 33 [9] C. Gu, Z, Zhang, S. Sun, Y. Pan, C. Zhong, Y. Lv, M. Li, K. Ariga, F. Huang, Y. Ma, Adv. Mater. 24, 34 5727 (2012). 35 [10] M. Li, S. Ishihara, M. Akada, M. Liao, L. Sang, J. Hill, V. Krishnan, K. Ariga, Y. Ma, J. Am. Chem. Soc. 36 133, 7348 (2011). 37 38 39 40 41 42 43 44 45

46

Ultralong Organic Phosphorescence

H-aggregation

1 Ultralong Organic Phosphorescence 1 1,22 Zhongfu An , Wei Huang

3 1Key Laboratory of Flexible Electronics (KLOFE) & Institute of Advanced Materials (IAM), Jiangsu

4 National Synergetic Innovation Center for Advanced Materials (SICAM), Nanjing Tech University

5 (NanjingTech), 30 South Puzhu Road, Nanjing 211816, China

6 2Institute of Flexible Electronics (IFE)

7 Northwestern Poly technical University (NPU), 127 West Youyi Road, Xi'an 710072, China

8 E-mail: iamzfan@njtech.edu.cnof institution/department, Name of University, City (Country)

9

10 Organic phosphorescence materials are generating great excitement over the past decade due to

11 their outstanding optoelectronic features such as ultralong luminescence lifetime, large Stokes shift,

12 and environmental sensitivity, lending them to various applications in organic light-emitting diodes,

13 organic solar cells, bio/chemo-sensors and bioimaging. However, the task of generating excited

14 states with long lifetimes has been met with limited success, due to the ultrafast deactivation of the

15 highly active excited states. Despite substantial success, there still exist a number of formidable

16 challenges.

17 Here we present a rational design rule to tune the emission lifetime of a wide range of luminescent

18 organic molecules, based on effective stabilization of triplet excited states via strong coupling in H-

19 aggregated molecules (Figure 1)[1-5]. Our experimental data revealed that luminescence lifetimes up

20 to 2.45 s, which are several orders of magnitude longer than those of conventional organic

21 fluorophores, can be realized under ambient conditions. These results outline a fundamental

22 principle to design organic molecules with elongated lifetimes of excited states, providing a major

23 step forward in expanding the scope of organic phosphorescence applications.

24

25 26 Figure1 Concept for ultralong organic phosphorescence materials

27 [1] ZF. An, C. Zheng, Y. Tao, RF. Chen*, HF. Shi, T. Chen, ZX. Wang, H. Li, R. Deng, XG. Liu*, W. Huang*,

28 Nat. Mater. 14, 685-690. (2015)

29 [2] SZ. Cai, HF. Shi, JW. Li, L. Gu, Y. Ni, Z. Cheng, S. Wan, WW. Xiong, L. Li, ZF. An*, W. Huang*, Adv.

30 Mater. 29, 1721244. (2017)

31 [3] SZ. Cai, HF. Shi, ZY. Zhang, X. Wang, HL. Ma, N. Gan, Q. Wu, ZC. Cheng, K. Ling, MX. Gu, An, ZF.

32 An*, W. Huang*, Angew. Chem. Int. Ed. 57, 4005-4009. (2018)

33 [4] LF.Bian, HF. Shi, X. Wang, K. Ling, HL. Ma, MP. Li, ZC. Cheng, C. Ma, S. Cai, Q. Wu, N. Gan, ZF. An*,

34 W. Huang* J. Am. Chem. Soc. 140, 10734−10739. (2018)

35 [5] L. Gu, HF. Shi, L. Bian, MX. Gu, K. Ling, X. Wang, HL. Ma, SZ. Cai, W. Ning, L. Fu, F. Huo, Y. Tao, ZF

36 An*, XG. Liu*, W. Huang* Nat. Photon. Accepted. (2019)

37

Charge generation dynamics in efficient non-fullerene organic solar cells

Philip Chow

Department of Chemistry, The Hong Kong University of Science and Technology, Hong Kong (China)

Organic solar cells (OSCs) suffer large photovoltage losses compared to their inorganic counterparts, due to a large energy offset at the donor-acceptor (D/A) heterojunction and non-radiative charge recombination. OSCs based on fullerene acceptors engineered to reduce photovoltage losses show reduced quantum yield of charge generation. Recently, small photovoltage loss and nearly 100% charge generation yield have been achieved in OSCs based on non-fullerene acceptors with small D/A offsets, but the charge dynamics underlying these systems is unclear. In this talk, I will show our experimental results on charge generation dynamics in model non-fullerene systems with low photovoltage loss and near unity charge generation efficiency. By optically probing the time evolution of excited states, we showed that electrons and holes separate at the heterojunction via thermal activation of interfacial charge-transfer excitons (CTEs) on a hundred picosecond timescale, three orders of magnitude slower than typical fullerene systems. Our results show how it is possible to generate free charges from strongly bound excitons in organic semiconductors without the photovoltage losses usually considered to be associated with overcoming the Coulomb interaction and suggest that by cycling between excitons and free charges without energy losses, non-fullerene OSCs operate in a manner akin to non-excitonic inorganic solar cells and therefore have the potential to reach similar efficiencies.

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Synthesis, Optical and Electrochemical Properties of Phenanthrodithiophene (Fused‐Bibenzo[c]thiophene) Chromophore

Yousuke Ooyama

Department of Applied Chemistry, Graduate School of Engineering, Hiroshima University, Higashi‐Hiroshima (Japan)

Development of a new π‐building block has created considerable interest in recent years as a key constituent of emitters, semiconductors and photosensitizers for organic optoelectronic devices, such as organic light‐emitting diodes (OLEDs), organic field‐effect transistors (OFETs), organic photovoltaics (OPVs), and dye‐sensitized solar cells (DSSCs) [1‐3]. For this purpose, recently, we designed and developed a fused‐bibenzo[c]thiophene, namely, 2,9‐bis(tert‐butyldimethylsilyl)phenanthro[9,8‐bc:10,1‐b'c']dithiophene (PHDT‐Si) as a new π‐building block in the emitters, the photosensitizers and the semiconductors for organic optoelectronic devices (Fig. 1) [4]. Based on photophysical (photoabsorption, fluorescence and time‐resolved fluorescence spectroscopy) and electrochemical meaurement (cyclic voltammetry), and density functional theory (DFT) calculation, it was found that the fused‐bibenzo[c]thiophene PHDT‐Si which is prepared by an efficient synthetic method, has a rigid, high planar and expanded π‐conjugation structure, and possesses intense photoabsorption and fluorescence properties (λmax

abs = 598 nm (εmax = 41000 M‒1

cm ‒1) and λmaxfl = 613 nm (Φf = 0.74) in toluene) in long‐wavelength region (Fig. 2) and

electrochemically reversible oxidation process, compared to non‐fused 1,1'‐bis(tert‐butyldimethylsilyl)‐4,4'‐bibenzo[c]thiophene (BBT‐Si). Consequently, it was revealed that the significant red‐shift of the photoabsorption band for PHDT‐Si relative to BBT‐Si is attributed to not only destabilization of the HOMO energy level and but also stabilization of LUMO energy level due to the fused‐bibenzo[c]thiophene skeleton, resulting in a decrease in the HOMO–LUMO band gap. This work demonstrated that PHDT‐Si with the highly π‐conjugated system due to fusion of the two benzo[c]thiophene units possesses a stronger photoabsorption and fluorescence properties in long‐wavelength region, and lower oxidation potential, compared to BBT‐Si with the less π‐conjugated system due to twisting of the two benzo[c]thiophene units. We believe that the fused‐bibenzo[c]thiophene skeleton with the above advantage properties would be used as a π‐building blocks in the emitters, the photosensitizers and the semiconductors for organic optoelectronic devices. (a) (b) 50000

40000

30000

20000

10000

Fluo

resc

ence

Inte

nsity

(a.u

.) BBT-Si PHDT-Si

BBT-Si PHDT-Si

/M

-1cm

-1

0 300 400 500 600 700 800

Wavelength / nm

Fig 1. Chemical structures of fused‐ Fig 2. (a) Photoabsorption and fluorescence spectra bibenzo[c]thiophene PHDT‐Si and non‐ of BBT‐Si and PHDT‐Si in toluene. (b) Color (left) fused 4,4'‐bibenzo[c]thiophene BBT‐Si. and fluorescence color (right) images (under 365

nm irradiation) of BBT‐Si and PHDT‐Si in toluene.

[1] M. E. Cinar and T. Ozturk, Chem. Rev., 115, 3036 (2015). [2] M. Stępień, E. Gońka, M. Żyła and N. Sprutta, Chem. Rev., 117, 3479 (2017). [3] K. Kawabata, I. Osaka, M. Sawamoto, J. Zafra, P. M. Burrezo, J. Casado and K. Takimiya, Chem. Eur. J., 23, 4579 (2017). [4] Y. Ooyama, T. Enoki, S. Aoyama, and J. Ohshita, Org. Biomol. Chem., 15, 7302 (2017).

r AT~t -\. c~! J?I I ... '- s Lt ,> Merocyanine .

:R1- N ~ CN ,' PEDOT:PSS:t6 ::::;;:::::-,t.......J : R2 NC / ITO-,___________________ A

20 H

c~ 30 nm

~o ~ o ~~ ~ .... s"!llio~o~~~ _,_a_oo l/ nm

1 Ultra‐narrow Bandwidth Organic Photodiodes by Exchange Narrowing in Merocyanine 2 H‐ and J‐aggregate Excitonic Systems 3 4 Matthias Stolte,#1,2 Andreas Liess,1,2 Alhama Arjona‐Esteban,1 Astrid Kudzus,2 Julius Albert,2

5 Ana‐Maria Krause,2 Aifeng Lv,2 David Bialas,1,2 Vladimir Stepanenko,1,2 Frank Würthner*1,2

6 7 1Institut für Organische Chemie and 2Center for Nanosystems Chemistry 8 Julius‐Maximilians‐Universität Würzburg, 97074 Würzburg (Germany) 9 #e‐mail: matthias.stolte@uni‐wuerzburg.de

10 *e‐mail: wuerthner@uni‐wuerzburg.de 11 12 The solid‐state packing structure of π‐conjugated organic molecules highly affects the materials’ 13 properties.[1] For merocyanine dyes, usually arranging in an H‐coupled antiparallel fashion,[2] more 14 interesting J‐coupling structures have rarely been reported. Here we show for nine highly dipolar 15 merocyanine dyes with the same π‐scaffold and thus equal monomer properties in solution, that the 16 packing arrangement can be controlled by the bulkiness of the donor substituent, leading to strong 17 exciton coupling within a card stack (H) or zig zag (J) packing.[3]

18 19 Figure 1. Application of merocyanine dyes in planar heterojunction photodiodes with corresponding 20 EQE data of the best devices exhibiting an ultranarrow H‐ or J‐band.

21 Both bands in the blue (H) and NIR (J) spectral ranges arise from a single exciton band and are not 22 just a mere consequence of different polymorphs within the same thin film. By fabrication of organic 23 thin‐film transistors, these dyes are demonstrated to exhibit hole transport behavior in spin‐coated 24 thin films. Moreover, when used as organic photodiodes in planar heterojunctions with C60 fullerene, 25 they show wavelength‐selective photocurrents with external quantum efficiencies up to 11 % and 26 ultra‐narrow bandwidths down to 30 nm.[4] Thus, narrowing the linewidths of optoelectronic 27 functional materials by exciton coupling provides a powerful approach to yield ultra‐narrowband 28 organic photodiodes. 29 30 References 31 [1] M. Irimia‐Vladu, Chem. Soc. Rev. 43, 588 (2014). 32 [2] F. Würthner, Acc. Chem. Res. 49, 868 (2016). 33 [3] A. Liess, A. Lv, A. Arjona‐Esteban, D. Bialas, A.‐M. Krause, V. Stepanenko, M. Stolte, F. Würthner, 34 Nano Lett. 17, 1719 (2017). 35 [4] A. Liess, A. Arjona‐Esteban, A. Kudzus, J. Albert, A.‐M. Krause, A. Lv, M. Stolte, K. Meerholz, F. 36 Würthner, Adv. Funct. Mater. DOI: 10.1002/adfm.201805058 (2019).

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Electronic structure,morphology,andflexibilityof conjugatedpolymers: Insights from time-resolved electron paramagneticresonancespectroscopy

Clemens Matt1,Deborah L. Meyer

1,Michael Sommer

2, Till Biskup1

1Institut für Physikalische Chemie, Albert-Ludwigs-Universität Freiburg, Freiburg (Germany)

2Institut für Chemie,Polymerchemie,Technische Universität Chemnitz,Chemnitz (Germany)

The interplay between electronic structure, morphology, flexibility, and local ordering, while at the heart of structure–function relationship of organic electronic materials, is still barely understood. Time-resolved electron paramagnetic resonance (TREPR) spectroscopy has proven valuable to gain further insight. Here, short-lived light-induced paramagnetic states such as charge-transfer states and triplet excitons, are directly accessible and can be used as a sensitive probe for their immediate molecular environment. This contribution focuses on our recent work on triplet excitons of conjugated polymers and presents a series of showcases for the insights available. Morphology in films is considered one of the crucial parameters of device efficiency, besides electronic structure and energy level matching. Due to their intrinsic anisotropy, triplet states can be used to reveal both, orientation and degree of ordering of a polymer film [1], nicely complementing other methods for structure determination. Here, we could show a rather amorphous polymer (PCDTBT) to exhibit strong orientation and ordering when cast as film on a rigid substrate. The role of triplet states for device efficiency is still highly debated. TREPR spectroscopy, due to its direct access to triplet states, is well suited to probe the origin of these states. This brought a seemingly forgotten route back into focus: spin-forbidden direct S0→T excitation, with potential high impact for device efficiency [2,3]. Exciton delocalization is another parameter crucial for the efficiency of organic semiconductors. Combined with density-functional theory (DFT) calculations, TREPR spectroscopy can be used to discriminate between electronic structure and planarity when it comes to determining factors for exciton delocalisation [4, 5]. Additionally, magnetophotoselection experiments allow to directly probe the mode of exciton delocalisation, be it along the polymer backbone or parallel to the π–π stacking direction [6]. Finally, we show the intrinsically high sensitivity of TREPR spectroscopy to the local environment of the triplet exciton to make it an excellent tool for investigating polymer morphology. The parameters readily available from spectral simulations allow us to probe the available conformational subspace of the polymer backbone and thus the degree of order even in solution and as a function of the solvent [4, 7]. This provides crucial insight into parameters for solution processing of polymers.

[1] T. Biskup, M. Sommer, S. Rein, D. L. Meyer, M. Kohlstädt, U. Würfel, and S. Weber, Angew. Chem. Int. Ed. 54,7707–7710. (2015) [2] D. L. Meyer, F. Lombeck, S. Huettner, M. Sommer, and T. Biskup, J. Phys. Chem. Lett. 8, 1677– 1682. (2017) [3] C. Matt, D. L. Meyer, F. Lombeck, M. Sommer, and T. Biskup, Mol. Phys., doi:10.1080/00268976.2018.1523479. (2018) [4] D. L. Meyer, R. Matsidik, M. Sommer, and T. Biskup, Phys. Chem. Chem. Phys. 20, 2716–2723. (2018) [5] C. Matt, D. L. Meyer, F. Lombeck, M. Sommer, and T. Biskup, Macromolecules 51, 4341–4349. (2018) [6] D. L. Meyer, R. Matsidik, D. Fazzi, M. Sommer, and Till Biskup, J. Phys. Chem. Lett. 9, 7026–7031. (2018) [7] D. L. Meyer, R. Matsidik, S. Huettner, M. Sommer, and T. Biskup, Adv. Electron. Mater. 4, 1700385. (2018)

1 Azulene-Based Organic Semiconductors

2

3 Hanshen Xin, Xike Gao*

4

5 Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences, Shanghai 200032, China

6

7 gaoxk@mail.sioc.ac.cn

8

9 Azulene has earned considerable attention due to its unique chemical structure and unusual

10 properties, including a large dipole moment of 1.08 D, long-wavelength weak absorption (S0→S1)

11 with narrow HOMO–LUMO energy gap, as well as abnormal fluorescence (anti-Kasha’s rule, S2→S0)

12 [1-3]. For all of these reasons, azulene and its derivaties have attracted more and more attention in

13 chemical, biological and material science. In recent years, azulene and its derivatives have gained

14 increasing attention due to their successful applications in organic optoelectronic devices, such as

15 organic thin film transistors (OTFTs) and organic photovoltaics (OPVs) [1]. However, the development

16 of azulene-based organic optoelectronic materials is hampered by the difficulty in molecule design

17 and synthesis. Recently, we developed a class of azulene-based aromatic diimides, 2,2-biazulene-

18 1,1,3,3-tetracarboxylic diimides (BAzDIs), which are quite different from perylene diimides (PDIs) in

19 color and in physicochemical properties, although the difference in the chemical formulas between

20 BAzDIs and PDIs with the same R substituents is two extra hydrogen atoms for BAzDIs [4]. Some

21 latest developed BAzDI-based small molecular and polymeric semiconductors (Figure 1) have shown

22 2 V1high electron mobilities of up to 0.5 cm s1 in OTFTs and great potentialities in OPVs as electron

23 acceptors [5,6].

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26

NO O

NO O

BAzDI

R

R

N

N

O O

O O

R

R

Azulene

27 28

29 Figure 1. Application of azulene to construct BAzDI-based organic optoelectronic materials.

30

31

32

33 References

34 [1] H. Xin and X. Gao, ChemPlusChem. 82, 945-956 (2017).

35 [2] H. Xin, C. Ge, L. Fu, X. Yang, X. Gao, Chin. J. Org. Chem. 37, 711-719 (2017).

36 [3] H. Gao, X. Yang, H. Xin, T. Gao, H. Gong, X. Gao, Chin. J. Org. Chem. 38, 2680-2692 (2017).

37 [4] H. Xin, C. Ge, X. Yang, H. Gao, X. Yang and X. Gao, Chem. Sci. 7, 6701-6705 (2016).

38 [5] H. Xin, J. Li, C. Ge, X. Yang, T. Xue and X. Gao, Mater. Chem. Front. 2, 975-985 (2018).

39 [6] H. Xin, C. Ge, X. Jiao, X. Yang, K. Rundel, C. R. McNeill and X. Gao, Angew. Chem. Int. Ed. 57, 1322-

40 1326 (2018).

41

•

1 Crosslinkableconjugatedpolymersfororganicelectronics 2 3 Peter Strohriegl1,Christina Saller1, Sonja Dziewior1, Christian Beck1,Anna Köhler2,Frank-Julian Kahle2

4 5 1

Macromolecular Chemistry I, University of Bayreuth, Germany 6 2

Soft Matter Optoelectronics, University of Bayreuth, Germany 7 8 Semiconducting polymers have gained large interest during the last decades due to potential 9 applications in organic solar cells (OSCs), organic light emitting diodes (OLEDs), and electronic circuits

10 based on organic field effect transistors (OFETs). Among these materials low bandgap polymers have 11 been successfully used as active layers in bulk heterojunction organic solar cells (OSCs) reaching above 12 12% efficiency. Bulk heterojunction solar cells usually have one active layer consisting of a blend of a 13 low bandgap donor polymer and a low molar mass acceptor like PCBM. An alternative concept to 14 efficient OSCs are multilayer cells prepared by successive vacuum deposition of organic donor and 15 acceptor materials which have meanwhile reached efficiencies of 13%. The preparation of such 16 multilayer OSCs is currently a domain of vacuum evaporable low molar mass materials. 17 Our approach to solution processable multilayer OSCs and to the stabilization of BHJ solar cells is the 18 synthesis of low bandgap polymers like PCDTBT with crosslinkable units [1]. In the talk, the synthesis 19 of crosslinkable low bandgap polymers as well as the crosslinking process will be presented in detail. 20 Furthermore we will present a multilayer organic solar cell with a crosslinked exciton blocking layer 21 [2], and discuss the influence of crosslinking on the diffusion of C60 in conjugated polymers [3,4]. A 22 quantitative study on the effects of chemical crosslinking on the fluorescence and the charge carrier 23 mobility in a series of polyfluorenes will be presented [5]. 24

O O

O O

S N N

S S n

(Initiator)

C6H13 C6H13

polymerisable groups crosslinks

Conjugated polymer with Densely crosslinked polymer Chemical structure of PCDTBTOx crosslinkable side groups network

soluble insoluble 25 26 Recently, we have extended the concept of crosslinking to perovskite solar cells and synthesized 27 crosslinkable derivatives of the hole transport materials poly(bis-(4-phenyl(2,4,6-trimethyl-

28 phenyl)amine) (PTAA) and Spiro-OMeTAD in order to suppress the diffusion of low molar mass dopants 29 in the hole transport layer. 30 31 [1] F.-J. Kahle, C. Saller, A. Köhler, P. Strohriegl, Adv. Energy Mater. 1700306 (2017) 32 [2] T. Hahn, C. Saller, M. Weigl, I. Bauer, T. Unger, A. Köhler, P. Strohriegl, Phys. Stat. Solidi, A 212,2162 (2015) 33 [3] F. Fischer, T. Hahn, H. Bässler, I. Bauer, P. Strohriegl, A. Köhler, Adv. Funct. Mater. 24,6172 (2014) 34 [4] C. Saller, F.-J. Kahle, T. Müller, T. Hahn, S. Tscheuschner, D. Priadko, P. Strohriegl, H. Bässler, A. Köhler, 35 ACS Appl. Mater. Interfaces 10,21499 (2018) 36 [5] F.-J. Kahle, I. Bauer, A. Köhler, P. Strohriegl, J. Polym. Sci. B, Polym. Phys. 55,112 (2017)

Understanding the microscopic mechanisms of carrier and exciton transport in organic 1

semiconductors 2

3

Yuqian Jiang1, Zhigang Shuai2 4

5 1 Laboratory for Nanosystem and Hierarchy Fabrication, CAS Center for Excellence in Nanoscience, 6

National Center for Nanoscience and Technology, Beijing 100084, People’s Republic of China 7 2 MOE Key Laboratory of Organic OptoElectronics and Molecular Engineering, Department of 8

Chemistry, Tsinghua University, Beijing 100084, People’s Republic of China 9

10

As the most important electronic processes in organic semiconductors, the underlying mechanisms in 11

charge transport and exciton transport are still in controversy. For understanding the microscopic 12

transport properties of carrier [1] and exciton [2], different methods covered from Semiclassical 13

Marcus theory, to quantum nuclear tunneling hopping model, to time-dependent wavepacket 14

(TDWPD) method have been comparably employed. In both carrier and exciton transport, Marcus 15

theory excluding the nuclear quantum effect can underestimate transport abilities, while quantum 16

hopping model and TDWPD method can both result to excellent predictions compared to 17

experiments by including the quantum effect of nuclear motion. For the system with relatively strong 18

carrier/exciton delocalization effect, TDWPD will predict much higher mobility or longer exciton 19

diffusion length than quantum hopping model. To this point, TDWPD method should be more 20

preferred for either carrier or exciton transport. Besides, the application of acoustic phonons 21

dominated band-like model on charge transport demonstrates that the fully delocalized picture can 22

greatly overestimate the carrier mobility, even for the systems with high mobility, such as rubrene, 23

DNTT, DATT, pentacene [1]. Therefore, we take the view that quantum nuclear tunneling effect 24

dominates both carrier and exciton transport in organic semiconductors. Moreover, we have 25

predicted that the negative isotope effect on charge transport can become the direct manifestation 26

of the nuclear quantum effect [3, 4]. 27

28

[1] Yuqian Jiang, Xinxin Zhong, Wen Shi, Qian Peng, Hua Geng, Yi Zhao, Zhigang Shuai*, Nanoscale 29

Horiz., 1, 53-59 (2016). 30

[2] Yuqian Jiang*, Zhigang Shuai*, Minghua Liu, J. Phys. Chem. C, 122, 18365-18375 (2018). 31

[3] Yuqian Jiang, Qian Peng, Hua Geng, He Ma, Shuai, Zhigang*, Phys. Chem. Chem. Phys., 17, 3273-32

3280 (2015). 33

[4] Yuqian Jiang, Hua Geng, Wen Shi, Qian Peng, Xiaoyan Zheng, Zhigang Shuai*, J. Physical Chem. 34

Lett., 5, 2267-2273 (2014). 35

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N-type copolymers for organic solar cells, transistors and thermoelectrics

R. Matsidik1, F. Nübling1, Y. Shin2, A. Luzio3, K. Deshmuk4, C. McNeill4, M. Caironi3, M. Sommer2

1Universität Freiburg, Makromolekulare Chemie, Stefan-Meier-Str. 31, 79104 Freiburg;

Germany 2Technische Universität Chemnitz, Institut für Chemie, Straße der Nationen 62, 09111

Chemnitz; Germany 3Center for Nano Science and Technology @PoliMi, Istituto Italiano di Tecnologia, Via Pascoli

70/3, 20133, Milano, Italy 4Department of Materials Science and Engineering, Wellington Road, Clayton, Victoria, 3800,

Australia

Recent years have witnessed great progress of n-type conjugated polymers in terms of structural diversity and modification, processing and application in all sub-areas of organic electronics. However, with step-growth polycondensation still being the dominant reaction mechanism, molecular weight (MW) control remains a major drawback, which complicates comparability of individual studies. Another issue pertains to the role of prevalent chemical defects that eventually form during direct arylation polycondensation (DAP) of aromatic monomers. Here we present high performance, defect-free n-type copolymers that can be made via DAP with a minimum of reaction steps and controlled MW weight[1-3] to address the predominant MW dependence on properties usually observed for short chain systems. Using selected examples of naphthalene diimide and diketopyrrolopyrrole copolymers, application in all-polymer organic photovoltaics[4,5], n-channel transistors and thermoelectrics[6,7] are presented, and the role of the mentioned molecular parameters is discussed.

[1] R. Matsidik R. Matsidik, H. Komber, A. Luzio, M. Caironi, M. Sommer, J. Am. Chem. Soc. 2015, 137,

6705–6711 [2] S. Broll, F. Nübling, A. Luzio, D. Lentzas, H. Komber, M. Caironi, M. Sommer, Macromolecules

2015, 48, 7481–7488. [3] R. Matsidik, H. Komber, M. Sommer, ACS Macro Lett. 2015, 4, 1346–1350. [4] K. D. Deshmukh, R. Matsidik, S. Prasad, N. Chandrasekaran, A. Welford, L. Connal, A. Liu, E. Gann, L. Thomsen, D. Kabra, J. Hodgkiss, M. Sommer, C. McNeill, ACS Applied Materials & Interfaces 2018, 10, 955-969. [5] K. D. Deshmukh, R. Matsidik, S. K. Prasad, A. C. Y. Liu, E. Gann, L. Thomsen, J. M. Hodgkiss, M. Sommer, C. R. McNeill, Adv. Funct. Mater. 2018, 28, 1707185. [6] Y. Shin, A. Welford, H. Komber, R. Matsidik, T. Thurn-Albrecht, C. McNeill, M. Sommer, Macromolecules 2018, 51, 984-991. [7] D. Nava, Y. Shin, M. Massetti, X. Jiao, T. Biskup, J. Sangarashettyhalli, C. Madan, A. Calloni, L. Duò, G. Lanzani, C. McNeill, M. Sommer, M. Caironi. ACS Appl. Energy Mater. 2018, 1, 4626-4634.

Printed Organic Electronics – Problems and Perspectives

Beata Luszczynska1, Krzysztof Matyjaszewski1,2 , Jacek Ulanski1

1Department of Molecular Physics, Lodz University of Technology , 90-924 Lodz (Poland) 2Department of Chemistry, Carnegie Mellon University, Pittsburgh, PA 15213 (USA)

Possibility of printing organic electronic devices has been a driving force for the intensive research on organic electronics, nevertheless it still remains as an unfulfilled promise. In spite of tremendous progress in synthesis of new soluble and high performance organic semiconductors, the technology of printing electronics cannot overcome laboratory scale. In this talk we will present briefly the selected main obstacles limiting scale up of printed organic electronics, related to synthesis and processing of solution processable components, such as: - difficulties in high precision synthesis of organic semiconductors on large scale; - problems with controlling morphology of active layers in a reproducible way; - insufficient understanding of mechanisms of generation and transport of charge carriers and excitons and correlation of these mechanisms with chemical structure and morphology of active layers; - lack of high quality, solution processable and printable functional components, such as: dielectrics, elastic and transparent electrodes with desired work function, or high performance barrier materials; - difficulties in fabrication by solution based techniques multilayer structures, comprising also interlayers facilitating injection of charge carriers with desired sign and blocking injection of charge carriers with opposite sign; - lack of efficient, industrial scale technology of assembling organic and hybrid components into working, functional electronic devices. We will present perspectives of overcoming these problems, basing on critical analysis prepared by leading specialists in the field of organic electronics, published in the book “Solution-Processable Components for Organic Electronics”, B. Luszczynska, K. Matyjaszewski and J. Ulanski, Eds., Wiley-VCH, 2019.

Acknowledgments: The authors acknowledge support by the grants TANGO2/340019/NCBR/2017 and NCN Maestro UMO-2014/14/A/ST5/00204 (Poland), and by European grant 674990 EXCILIGHT -H2020-MSCA-ITN-2015.

PTB7-Th

0 N O CaHnY

···················1

C10H21 0 N 0 CaH11y

PNOI-T10 c,,H,, Large-area PSC

1 Molecular Design and Synthesis towards High-performance All-Polymer Solar Cells

2 -mandatory blank line-

3 Ergang Wang

4 -mandatory blank line-

5 Department of Chemistry and Chemical Engineering, Chalmers University of Technology, Gothenburg,

6 Sweden

7 -mandatory blank line-

8

9 All-polymer solar cells (all-PSCs) have attracted great interests in the past few years due to their

10 advantages over conventional fullerenes-based PSCs. Among a few successful all-PSCs that have been

11 reported, one of the key limiting factor is the low open-circuit voltage (Voc) (normally < 1 V), which is

12 strongly correlated with the energy level alignment of the donor and acceptor combinations. We

13 used a combination of a new donor polymer with an acceptor polymer PNDI-T to realize high-

14 performance all-PSCs with a high Voc of 1.10 V and a decent power conversion efficiency (PCE) of 8%,

15 which are even higher than the performance of the corresponding PCBM-based PSCs. In the further

16 work, a ternary all-PSC containing 3 polymers with complementary absorption spectra was

17 developed, which presents a high PCE of 9%. Power conversion efficiencies (PCEs) of 8.61% and high

18 fill factors of 0.71 are achieved by doctor-blading under a simple and energy-effective processing

19 conditions. Moreover, it was found the fluorination of the acceptor polymers can increase the

20 dielectric constant of the blends and thus the photocurrent of the all-PSCs. This could be a facile

21 method to further improve the performance of all-PSCs.

22

23 24 Figure 1. The chemical structures of the polymers and the device architecture and processing.

25

26

27 References

28 [1] X. Xu, Z. Li, W. Zhang, X. Meng, X. Zou, D. Di Carlo Rasi, W. Ma, A. Yartsev, M. R. Andersson, R. A. J.

29 Janssen, E. Wang, Adv. Energy Mater. 8, 1700908. (2018)

30 [2] Z. Li, W. Zhang, X. Xu, Z. Genene, D. Di Carlo Rasi, W. Mammo, A. Yartsev, M. R. Andersson, R. A. J.

31 Janssen, E. Wang, Adv. Energy Mater. 7, 1602722. (2017).

32 [3] Z. Li, X. Xu, W. Zhang, X. Meng, Z. Genene, W. Ma, W. Mammo, A. Yartsev, M. R. Andersson, R. A.

33 J. Janssen, E. Wang, Energy & Environ. Sci. 10, 2212. (2017).

34 [4] Y. Lin, S. Dong, Z. Li, W. Zheng, J. Yang, A. Liu, W. Cai, F. Liu, Y. Jiang, T. P. Russell, F. Huang, E.

35 Wang, L. Hou, Nano Energy 2018, 46, 428-435.

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40 This is the last line of your abstract.

Functional π-Electron Systems14th International Symposium on

Abstracts Poster Presentation

Plenary Lectures

Tuesday, June 4th

Paradigm Shift in n-Doping of Low Electron Affinity Organic Semiconductors

Antoine Kahn

Department of Electrical Engineering, Princeton University, Princeton, NJ 08544, USA

The controlled introduction of dopants in organic semiconductors enhances bulk conductivity,

improves carrier mobility and lowers contact resistance, enabling the design of high-performance

devices. Considerable progress has recently been made on the synthesis of high performance

molecular redox agents, allowing efficient n- and p-doping of organic semiconductors with a broad

range of electron affinities (EA) and ionization energies (IE). Of particular interest is the

development of relatively air-stable n-dopants. Traditional one-electron reductants able to n-dope

semiconductors used in a variety of applications must have low ionization energy, and are

therefore easily oxidized and unstable in ambient. We focus here on a series of new dopants

based on dimers of highly reducing organometallic species, whereby the air-stable dimer reacts to

yield two monomer cations and two electrons [1]. We discuss the process of photo-activation that

leads to dimer cleavage and n-doping of low EA semiconductors. We then focus on three

applications: (i) bulk n-doping of a series of OLED electron transport materials [2]; (ii) surface n-

doping of graphene for electron injection in organic semiconductors; and (iii) solution doping of

several low EA polymers.

[1] G. Song, S.-B. Kim, S. Mohapatra, Y. Qi, T. Sajoto, A. Kahn, S. R. Marder, S. Barlow, Adv.

Mat. 24, 699 (2012)

[2] X. Lin, B. Wegner, K. M. Lee, M. A. Fusella, F. Zhang, K. Moudgil, B. P. Rand, S. Barlow, S.

R. Marder, N. Koch and A. Kahn, Nature Materials 16, 1209 (2017)

Achieving non-fullerene organic solar cells with over 16% efficiency: material

design, device optimization and mechanism study.

He Yan

Department of Chemistry

Hong Kong University of Science and Technology

Non-fullerene organic solar cells offer several advantages over conventional fullerene

devices. Among them, one attractive feature of non-fullerene organic solar cells is the

low voltage loss from the optical bandgap of the active layer to the open circuit

voltage of the cell. In our research, we have developed material systems that can

achieve highly efficient charge separation with a small energy offset between the

donor acceptor materials. Such material systems can achieve low voltage loss of about

0.5 to 0.55 V, which, in theory, could enable non-fullerene organic solar cell near 20%

efficiency. In the first aspect of our study, we use transient absorption spectroscopy to

understand why non-fullerene organic solar cells can work well with small energy

offsets. Our results show that the key factor is the long CT life-time that allows for

efficient charge separation despite of a small energy offset. In the other aspect, we

study structure-property relationship of high-performance donor and non-fullerene

acceptor materials and reveal the key structure features that enable highly efficient

non-fullerene organic solar cell devices with over 16% efficiency. With these

understandings of mechanism and structure-property relationship, it is feasible to

further increase the efficiency of organic solar cells to the range of 18 to 20% in near

future.

Functional π-Electron Systems14th International Symposium on

Abstracts Poster Presentation

Invited Lectures

Tuesday, June 4th

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Designing solution-processed photonic light- and heat-management structures for solution-processable and printable organic optoelectronic devices

Natalie Stingelin

School of Materials Science & Engineering and School of Chemical & Biomolecular Engineering,

Georgia Institute of Technology, Atlanta (USA)

An ever increasing interest in the development and application of innovative optical and optoelectronic devices places greater emphasis for the advancement of new smart and functional materials that are readily processable. Significant progress has already been realized in the fields of organic light-emitting diodes (OLEDs) and photovoltaic cells (OPVs) through development of novel semiconducting materials. Here we discuss developments and advancements in materials design towards photonic structures that aid and improve light management in organic and inorganic/organic hybrid devices, with focus on solar cells. We cover systems targeted for use in light in-coupling structures, anti-reflection coatings, and beyond. Extension to architectures for heat management, important for a broad range of photovoltaic device platforms, including inorganic, inorganic/organic hybrid and organic devices, will also be presented.

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Towards complex 3D carbon-sulfur structures

E. Mena-Osteritz, P. Bäuerle

Institute of Organic Chemistry II and Advanced Materials / University of Ulm / Ulm (Germany)

Oligothiophenes represent an important class of compounds in the field of organic semiconductors and organic electronics. On the basis of thiophenes, we are currently synthesizing and investigating novel conjugated architectures and shapes, such as linear, macrocyclic, dendritic, and fused.

In particular, we have recently developed series of novel S,N-heteroacenes up to a 13-mer which combine the stability of oligothiophenes and the planar extended -system of (phen)acenes.[1] Conjugated materials with highly interesting optoelectronic properties,[2] small bond length alterna-tion, planarity, and good charge transport properties result in interesting structure-property relation-ships.

Opposite to these typically flat and extended -conjugated structures, we currently develop and syn-thesize 3-dimensional and sterically crowded thienylene-phenylenes in order to elucidate how in-creasing steric congestion influences the electronic properties.

Both classes of compounds were implemented in highly efficient organic [3] or perovskite solar cells.[4]

[1] C. Wetzel, E. Brier, A. Vogt, A. Mishra, E. Mena-Osteritz and P. Bäuerle, Angew. Chem. Int. Ed., 54, 12334 (2015). [2] C. Wetzel, A. Vogt, A. Rudnick, E. Mena-Osteritz, A. Köhler and P. Bäuerle, Org. Chem. Front., 4, 1629 (2017). [3] T. Leitner, A. Vogt, D. Popović, E. Mena-Osteritz, K. Walzer, M. Pfeiffer and P. Bäuerle, Mater. Chem. Front., 2, 959 (2018). [4] D. Bi, A. Mishra, P. Gao, M. Franckevicius, C. Steck, S. M. Zakeeruddin, M. K. Nazeeruddin, P. Bäuerle, M. Grätzel and A. Hagfeldt, ChemSusChem, 9, 433 (2016).

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Evolution of orbital state upon assembling the molecules on the surface

Satoshi Kera

Institute for Molecular Science, Okazaki (Japan), SOKENDAI, The Graduate University for Advanced Studies, Okazaki (Japan), Chiba University, Chiba (Japan)

Functional organic molecule (FOM) has recently attracted considerable attention both on

fundamental research and device applications because of peculiar properties not found in inorganics

and small molecules. However the mechanisms and its origin of various device characteristics are still

under controversial. Scientific mysteries would be raised because people have believed that

electronic structure of FOM would be conserved or at least approximated as in an isolated molecule

for solid state due to weak van der Waals interaction. To reveal characteristics of FOM the key

investigation would be on precise experiments on the electronic structure at various interfaces,

including organic-organic and organic-inorganic (metal/semiconductor) contacts.

High-resolution angle-resolved photoelectron spectroscopy of organic monolayer and bilayer films of

perfluoropentacene (PFP) prepared on Ag(111) and graphite substrates are performed to reveal the

impact of weak electronic interaction and strong electron-phonon coupling on the molecular orbital

states [1]. By comparing two weakly interacting interfaces, we confirm the localization of wave-

function spread of each state at the physisorbed interface and shed light on the character of an

electron cloud, namely delocalization of wavefunction of pi orbital, in functional molecular materials.

Recent results taken by the momentum microscopy which allows to give a global view of an electron

cloud in very short experimental time, which is quite important parameter in measuring the

electronic states of FOM due to irradiation damages, will be shown to discuss.

[1] S. Kera, N. Ueno, J. Electron. Relat. Phenom. 204, 2 (2015)

Polythiophene derivatives as mixed organic ionic and electronic conductors

Christine Luscombe,1,2 Jon Onorato1

1Materials Science and Engineering Department, University of Washington, Seattle, WA 98195-2120,

USA 2Institute of Molecular Engineering and Sciences, University of Washington, Seattle, WA 98195-1652,

USA

Mixed organic ionic and electronic conductors are being explored for a wide range of applications,

from bioelectronics to neuromorphic computing, artificial muscles and energy storage applications.

These materials exploit the simultaneous transport properties of ionic and electronic carriers to

enable novel device functions. Recently, polymer semiconductors have received significant amounts

of attention because of their flexibility, biological compatibility and ease of fabrication. These

materials, particularly thiophene-based polymers such as poly(3,4-ethylenedioxythiophene)-

poly(styrenesulfonate) (PEDOT:PSS) and related derivatives, have demonstrated significant

enhancements in performance in a relatively short amount of time, with transconductance values of

PEDOT:PSS transistors surpassing those achieved even with graphene.

Through our NSF Designing Materials to Revolutionize and Engineer our Future (DMREF) award with

researchers at Cornell University and the University of Chicago, we have been investigating the

synthesis of ethylene-glycol functionalized polythiophenes, their thin film morphology, and their

ionic and electronic conductivities, and comparing against theoretical predictions. Specifically, two

repeat unit structures were synthesized, one with an oxygen atom directly conjugated to the

polythiophene backbone (P3EGT), and one with a methylene spacer between the initial oxygen atom

and the polythiophene backbone (P3MEGT). Using molecular dynamics (MD) simulations, we

demonstrate that the crystalline version of P3MEGT has a lower ionic conduction than P3EGT. This

occurs because P3MEGT shows Li+ ion caging, whereas P3EGT side-chains don’t possess this caging

due to a reduced range-of-motion. To investigate their structural evolution with Li+ introduction, the

polymers were blended with lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) and studied using

grazing incidence wide angle X-ray scattering (GIWAXS). From this, it was determined that

introduction of LiTFSI results in both a reduction in crystallinity and expansion of the side-chain

stacking direction. Further, it is shown that lithium is present in both the crystalline and amorphous

regions at low loadings, though the crystalline region saturates at high loadings. The ionic conduction

was measured using electrochemical impedance spectroscopy, determining that ionic conduction

occurs predominantly in the amorphous domains for both polymers. Further, the measurements

show that P3MEGT has a higher ionic conduction for all conditions, a result consistent with MD

simulations. Collectively, this work provides a means to control and study the influence of polymer

backbone chemistry on the ionic conductivity of conjugated polymers [1].

[1] R. Giridharagopal, L. Q. Flagg, J. S. Harrison, M. E. Ziffer, J. Onorato, C. K. Luscombe, D. S. Ginger,

Nature Materials 16, 737. (2017).

Adventure of Electroactive/Photoactive Organic Thin Films on Flatland

Jianbin Xua, c, † and Qian Miaob, c, †

aDepartment of Electronic Engineering and Materials Science and Technology Research CenterbDepartment of Chemistry, and Materials Science and Technology Research Center

The Chinese University of Hong Kong, Hong Kong SAR cInstitute of Molecular Functional Materials†

Xinran Wangd

dNational Laboratory of Solid State Microstructures, School of Electronic Science and Engineering, and Collaborative Innovation Center of Advanced Microstructures, Nanjing University

Nanjing 210093, China

Wei Jie

eDepartment of Physics and Beijing Key Laboratory of Optoelectronic Functional Materials & Micro-nano Devices, Renmin University of China, Beijing 100872, China

jbxu@ee.cuhk.edu.hk

ABSTRACT

In this talk, we will present the recent progress in electroactive/photoactive organic thin films towards 2-dimensional (2D) limit. We will show our understanding of the electronic and optoelectronic properties of the ultrathin films on atomically flat substrates. Charge transport and photoluminance properties will be the primary topics to be elaborated. 2D-limit samples include epitaxially grown molecules, namely pentacene, 2,7-Dioctyl[1]benzothieno[3,2-b][1]benzothiophene (C8-BTBT), and N, N-ditridecylperylene-3,4,9,10-tetracarboxylic diimide (PTCDI-C13). The strategy here is applicable for various other electroactive and photoactive molecules.

ACKNOWLEDGEMENT

This work is made possible in collaboration with Drs. L. Shan, D. W. He, Y. H. Zhang, Z. F. Chen, Mr. X. Xu, et al. The work is in part financially supported by Research Grants Council of Hong Kong, particularly, via Grant Nos. AoE/P-03/08, 14204616, 14203018, N_CUHK438/18, and CUHK Group Research Scheme, CUHK Postdoctoral Fellowship.

[1] L. Shan, et al., Advanced Materials 27 (22), 3418 (2015) [2] Y. H. Zhang, et al., Physical Review Letters 116, 016602 (2016) [3] D. W. He, et al., Science Advances 3 (9), e1701186 (2017) [4] X. L. Liu, et al., Advanced Materials 28 (26), 5200 (2017) [5] X. R. Wang, et al., submitted; X. Xu, et al., submitted (2019)

†Areas of Excellence Scheme, University Grants Committee (Hong Kong), Grant No. AoE/P-03/08.

Modeling electronic processes in organic materials: organic

phosphorescence and organic thermoelectrics

Zhigang Shuai1

1 Tsinghua University, Department of Chemistry, Beijing, China

Electronic processes govern the optoeletronic properties for the pi-conjugated

systems. Through computational investigations, we present our basic understandings

for the aggregation-induced room temperature organic phosphorescence and present a

theoretical descriptor for the efficiency and afterglow lifetime which is helpful for

molecular design. Secondly, we present a study on the molecular design strategy for

efficient n-type thermoelectric organic coordination polymers. We find the

polaron band formation splitted from conduction leads not only to elevated seebeck

coefficient and thermopower, but also non-monotonic temperature behavior.

Bias-Stress-Induced Charge Trapping in Organic Transistors:

A Molecular Structure Perspective

Kilwon Cho

Pohang University of Science and Technology / Dept. of Chemical Engineering

Pohang, Korea

Operational instability of organic field-effect transistors (OFETs) is one of the most critical obstacles to their practical use and commercialization. Prolonged operation of OFETs under an applied bias can cause a significant drop in the channel current and a continuous shift in the threshold voltage, which prohibit the normal operation of an electronic device. The bias-stress-driven electrical instabilities are attributed to charge carrier trapping inside the device. In this talk I will discuss the challenges and our progresses in understanding of charge trapping phenomena in OFETs. First, I will briefly introduce the charge trapping phenomenon and discuss how to improve it under using of polymer gate dielectrics. Effects of material characteristics of gate-dielectric polymers on the OFET operation will be focused. Next, I will introduce several approaches for analyzing charge traps at the semiconductor-dielectric interface. The latter part includes our recent studies using photoexcited charge collection spectroscopy, a novel experimental method to probe charge traps. The new spectroscopic method has been applied to investigate the relationships between charge traps and the chemical/physical structure of materials. Especially, I will overview the recently reported polymer semiconductors with high charge mobility yet low crystalline ordering, and present our recent results on bias-stress induced charge trapping for this type of polymer semiconductors. All these systematic study results on the bias instability of OFETs would contribute to unveiling the charge trapping mechanisms and to realizing the robust and practical OFETs eventually.

A dynamic picture of photovoltaic energy conversion

Elizabeth von Hauff

VU Amsterdam Department of Physics and Astronomy De Boelelaan 1081, 1081HV Amsterdam The Netherlands

e.l.von.hauff@vu.nl

Organic and hybrid semiconductors offer many advantages for energy conversion, saving and storage applications. However, the process of separating photo-generated charge carriers in organic photovoltaics (OPV) is generally less efficient than in conventional inorganic PV technologies due to the large binding energy of the photogenerated excitons and the spatially localized charge carriers in molecular semiconductors. This has motivated intense research into the basic processes that govern charge separation in OPV devices. An increasing number of experimental and theoretical reports show a correlation between molecular vibrational modes, charge delocalization, and the separation of photogenerated excitons. As a result, many researchers have recognised that the electrostatic band diagram of the donor-acceptor system is not sufficient to explain charge separation in OPV.

In this talk, evidence demonstrating dynamic charge separation in emerging photovoltaic devices, such as OPV and perovskite solar cells is discussed more generally in light of recent results from the theory of open quantum systems. These theoretical results point to the need for a self-oscillating internal degree of freedom, acting as a microscopic piston in order to explain how a solar cell behaves as a heat engine, producing an inexhaustible photovoltage and photocurrent under illumination. The dynamic picture of photovoltaic energy conversion opens up new possibilities for the design and development of efficient new energy transducers.

References should be listed as below [1] R. Alicki, D. Gelbwasser-Klimovsky, A. Jenkins, E. von Hauff, A dynamic picture of energy conversion in photovoltaic devices; arxiv:1901.10873

Exceeding Shockley–Queisser Limit with Singlet Fission Satish Patil

Solid State and Structural Chemistry Unit Indian Institute of Science, Bangalore

E-mail: spatil@iisc.ac.in

Multiexciton generation through singlet fission has the potential of exceeding Shockley– Queisser limit in photovoltaic devices. However, only very few materials suitable for singlet fission are available at present and the mechanism of inter- and intra-molecular singlet fission are not fully understood. Detailed knowledge regarding the processes is crucial for developing new materials. In this talk, I will present the molecular design and synthesis strategies to meet the exchange energy and morphology criteria for molecules to undergo singlet fission.

References:

1. Molecular Design Strategies for Efficient Intramolecular Singlet Exciton Fission, K.C.

Krishnapriya et al. ACS Energy Lett. 2019, 4, 192-202

2. Spin density encodes intramolecular singlet exciton fission in pentacene dimers, Nat. Comm. 2019, 10, 33

3. Is the Chemical Strategy for Imbuing “Polyene” Character in Diketopyrrolopyrrole-

Based Chromophores Sufficient for Singlet Fission? Tushita Mukhopadhyay et al. J.

Phys. Chem. Lett. 2017, 8, 984-991

4. Ultrafast bridge planarization in donor-!-acceptor copolymers drives

intramolecular charge transfer, Palas Roy et al. Nat. Comm. 2017, 8, 1716

Functional π-Electron Systems14th International Symposium on

Abstracts Poster Presentation

Contributed Lectures

Tuesday, June 4th

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1 Aqueous-processable organic photovoltaic materials and devices 2 3 Han Young Woo 4 5 Department of Chemistry, Korea University, Seoul 02841, Republic of Korea.

6 E-mail) hywoo@korea.ac.kr

7 8 Over the past few decades, organic solar cells (OSCs) have made a significant progress, showing their 9 great potential for low-cost, flexible, light weight, portable and large-area energy-harvesting devices.

10 In this contribution, we report the development of a desirable aqueous process for eco- and human-11 friendly fabrication of efficient and stable organic field-effect transistors (eco-OFETs) and polymer 12 solar cells (eco-PSCs). Intriguingly, the addition of a typical anti-solvent, water, to ethanol was found 13 to remarkably enhance the solubility of oligoethylene glycol (OEG) side chain-based electroactive 14 materials (e.g., the highly crystalline conjugated polymer PPDT2FBT-A and the fullerene monoadduct 15 PC61BO12). A water–ethanol cosolvent with up to 40 vol% of water provided an increased solubility 16 of PPDT2FBT-A from 2.3 to 42.9 mg mL−1 and that of PC61BO12 from 0.3 to 40.5 mg mL−1 . Owing to 17 2 V−1the improved processability, efficient eco-OFETs with a hole mobility of 2.0 × 10−2 cm s−1 and eco-18 PSCs with a power conversion efficiency of 2.05% were successfully fabricated. In addition, the eco-19 PSCs fabricated with water–ethanol processing were highly stable under ambient conditions, 20 showing the great potential of this new process for industrial scale application. To better understand 21 the underlying role of water addition, the influence of water addition on the thin film morphologies 22 and the performance of the eco-OFETs and eco-PSCs were studied in detail.[1,2]

23 24 Fig. 1 Aqueous-processable donor and acceptor molecules.

25 26 27 [1] T. L. Nguyen, C. Lee, H. Kim, Y. Kim, W. Lee, J. H. Oh, B. J. Kim, H. Y. Woo, Macromolecules 50, 4415 (2017).

28 [2] C. Lee, H. R. Lee, J. Choi, Y. Kim, T. L. Nguyen, W. Lee, B. Gautam, X. Liu, K. Zhang, F. Huang, J. H. Oh, H. Y.

29 Woo, B. J. Kim, Adv. Energy. Mater. 1802674 (2018).

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1 Thienopyrrole organic semiconductors for organic field effect transistors (OFETs) 2 3 Chandima Bulumulla, Ruwan Gunawardhana, Lakmal Gamage, Michael C. Biewer, Mihaela C. Stefan 4 5 Department of Chemistry and Biochemistry, The University of Texas at Dallas, Richardson, Texas, 6 75080 (USA) 7 8 Pyrrole is an excellent building block for the synthesis of organic semiconductors. However, 9 the synthesis of pyrrole based organic semiconductors is challenging because pyrroles are prone to

10 oxidation. The smallest S, N‐heteroacene, thieno[3,2‐b]pyrrole is a good building block for organic 11 semiconductors due to the high electron density, asymmetry, and easily modifiable NH group. 12 Moreover, we have shown that organic semiconductors from thieno[3,2‐b]pyrrole display “nearly‐13 ideal” OFET characteristics without compromising charge carrier mobilities or threshold voltages. [1] 14 We have varied the structure and topology to investigate the relatively under‐explored banana shape 15 thieno[3,2‐b]pyrrole ole semiconductors and the influence of the heteroatom. [1‐3] 16 Banana shaped donor‐acceptor molecules with benzothiadiazole, fluorinated 17 benzothiadiazole acceptors and thieno[3,2‐b]pyrrole donor (TP‐BT2T‐BT and TP‐FBT2T‐TP) have 18 been reported by our group (Figure 1), and the OFET parameters were evaluated in a bottom‐19 gate/bottom‐contact (BGBC) OFET architecture. Hole mobility of 0.08 cm2 V‐1 s‐1 was measured for 20 the molecule (TP‐BT2T‐BT) with benzothiadiazole as the acceptor. [1] The molecule containing 21 fluorinated benzothiadiazole (TP‐FBT2T‐BT) showed hole mobility of 1.57×10‐3 cm2 V‐1 s‐1. [2] 22 Lengthening conjugation by synthesizing conjugated polymers was employed to facilitate the 23 hole transport and to obtain comparatively stable semiconductors. Our group reported the donor‐24 acceptor polymer containing thienopyrrole donor and diketopyrrolopyroole acceptor, P(DPP‐TP) 25 (Figure 1), and the OFET parameters were evaluated with bottom‐gate/top‐contact (BGTC) OFET 26 architecture. An increase in hole mobility to 0.12 cm2 V‐1 s‐1 was observed for the polymer (P(DPP‐27 TP)) as compared to the conjugated small molecules. [4] 28 We will also report the synthesis and characterization of three organic semiconductors 29 containing terminal thieno[3,2‐b]pyrrole moieties and central aryl‐vinylene‐aryl units phenyl‐30 vinylene‐phenyl (PVP), furan‐vinylene‐furan (FVF) and thiophene‐vinylene‐thiophene (TVT). By 31 changing the aromatic group in the central unit, optical and electrochemical properties can be 32 systematically varied.

33 34 35 36 [1] C. Bulumulla, R. Gunawardhana, R.N. Kularatne, M.E. Hill, G.T. McCandless, M.C. Biewer, and M.C. 37 Stefan, ACS Applied Materials & Interfaces, 10, 11818‐11825. 2018. 38 [2] C. Bulumulla, R. Gunawardhana, S.H. Yoo, C.R. Mills, R.N. Kularatne, T.N. Jackson, M.C. Biewer, 39 E.D. Gomez and M.C. Stefan, Journal of Materials Chemistry C, 6, 10050‐10058. 2018. 40 [3] C. Bulumulla, R. Gunawardhana, P.L. Gamage, R.N. Kularatne, M.C. Biewer, and M.C. Stefan, 41 Synlett. 2018. 42 [4] C. Bulumulla, R.N. Kularatne, R. Gunawardhana, H.Q. Nguyen, G.T. McCandless, M.C. Biewer, and 43 M.C. Stefan, ACS Macro Letters, 7, 629‐634. 2018.

Figure 1. Pyrrole based donor‐acceptor small molecules and polymers for OFETs

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Efficient CsPbBr3 Perovskite Light-Emitting Diodes Enabled by Synergetic Device Architecture

Jianxin Tang

Institute of Functional Nano & Soft Materials (FUNSOM), Soochow University, Suzhou (China)

The development of solution-processed inorganic metal halide perovskite light-emitting diodes (PeLEDs) is currently hindered by low emission efficiency due to morphological defects and severe non-radiative recombination in all-inorganic perovskite emitters. In this talk, we weill introduce our recent progress on bright PeLEDs, where were obtained by synergetic morphology control over cesium lead bromide (CsPbBr3) perovskite films with the combination of two additives. The phenethylammonium bromide (PEABr) additive enables the formation of mixed-dimensional CsPbBr3

perovskites featuring the reduced grain size (<15 nm) and efficient energy funneling, while the dielectric polyethyleneglycol (PEG) additive promotes the formation of highly compact and pinhole-free perovskite films with defect passivation at grain boundaries. Consequently, green PeLEDs achieve a current efficiency of 37.14 cd/A and an external quantum efficiency of 13.14% with the maximum brightness up to 45990 cd/m2 and high color purity. Furthermore, this method can be effectively extended to realize flexible PeLEDs on plastic substrates with a high efficiency of 31.0 cd/A.

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1 Designing Quaternary Blended Organic Solar Cells with Over 13% Efficiencies 2

3 Chuanlang Zhan 4

5 1 College of Chemistry and Environmental Science, Hebei University, Baoding 071002, China.

6 2 CAS Key Laboratory of Photochemistry, Institute of Chemistry, Chinese Academy of Sciences,

7 Beijing 100190, China. 8

9 Bulk-heterojunction (BHJ) polymer solar cells (PSCs) which employ nonfullerene small-molecule as 10 the blended electron acceptor material are of particular interest in the field of solar energy applications. 11 Blending multi materials together such as ternary blended active layer extends light absorption and 12 optimizes electronic process, thus it is an alternative successful approach to promote the cell 13 performance by improving either short-circuit current-density (JSC), open-circuit voltage (VOC), or fill-14 factor (FF), which ultimately leads to a larger power conversion efficiency (PCE). The ternary 15 approach is normally achieved by mixing two donors either small-molecule or polymer with one 16 acceptor or one donor with two acceptors either two nonfullerene, or two fullerene, or the mixing of 17 fullerene and nonfullerene. Success on the design and synthesis of fused-ring electron acceptors 18 (FREAs) has led to a rapid advance in the fullerene-free PSCs. Though the ternary cases employing 19 FREA in its photo-active layer have proven the success in the JSC, VOC, FF and PCE, the enhancement 20 on the device PCE via employing the ternary approach approach has been limited within 10-20% for 21 most cases. Finding new mechanisms are therefore warranted. In this talk, we will show you our 22 concept, selection, and success in fabricating quaternary blended photo-active layer, so called 23 quaternary organic solar cells. 24

25 26

27

28 References 29 1. W. Liu, J. Yao, C. Zhan, Chin. J. Chem. 2017, 35 (12), 1813-1823. 30 2. W. Liu, W. Li, J. Yao and C. Zhan, Chin. Chem. Lett. 2018, 29 (3), 381-384. 31 3. D. Yan, W. Liu, J. Yao and C. Zhan, Adv. Energy Mater., 2018, 8, 1800204. 32 4. W. Li, D. Yan, F. Liu, T. Russell, C. Zhan and J. Yao, Sci. Chin. Chem. 2018, 61 (12), 1609-1618. 33 5. D. Yan, J. Xin, W. Li, W. Ma, J. Yao and C. Zhan, Acs Appl. Mater. & Interfaces, 2019, 34 10.1021/acsami.8b17246. 35 6. F. Shen, D. Yan, W. Li, H. Meng, J. Huang, X. Li, J. Xu and C. Zhan, Mater. Chem. Front., 2019, 36 10.1039/C8QM00571K.

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Mixed Sulfur/Selenium Fused π-Conjugated Materials for Organic Field-Effect Transistors

Brigitte Holzer,1 Berthold Stöger,2 Daniel Lumpi,1 Ernst Horkel,1 and Johannes Fröhlich1

1Institute of Applied Synthetic Chemistry, TU Wien (Vienna University of Technology), Vienna (Austria) 2X-Ray Centre, TU Wien (Vienna University of Technology), Vienna (Austria)

Organic semiconductors gained considerable scientific and commercial interest in recent years

due to various advantages compared to their inorganic counterparts. In particular fused thiophene-

based materials proved to be benchmark p-type organic semiconductors owing to their unique

electronic properties associated with their π-electron topology.[1] Essentially, the molecular packing

and intermolecular interactions of neighboring π-conjugated molecules crucially impact on the device

performance, which may be even enhanced by the integration of electron donating and highly

polarizable selenium. However, the development of reliable synthetic pathways toward selenium-

based materials is still matter of ongoing research owing to a lack of available starting materials.

Recently, several promising organic semiconductors based on benzothieno[3,2-b]thiophene 1a

[2] and benzothieno[2,3-b]thiophene subunits 2a [3, 4] (Figure 1, A) yielding charge carrier mobilities

up to 1 cm2V-1s-1 have been investigated. Based on these structural moieties, the topic of this

contribution focusses on the integration of selenium in these fused π-conjugated compounds leading

to semiconductors 1b-1d and 2b-2d (Figure 1). Reliable protocols towards regioisomeric selenophene-

based fused acenes will be presented starting from commercially available building blocks like

benzothiophene and benzoselenophene.

Figure 1: A Mixed thiophene/selenophene fused target compounds, B absorption spectra and

molecular structure of 1b.

Furthermore, photo-physical and electro-chemical properties of these target materials will be

probed by cyclic voltammetry, UV-Vis spectroscopy, and X-ray diffraction (Figure 1, B). The molecular

structures of all compounds will be investigated, and the molecular interactions will be correlated to

materials properties. Selected compounds will be characterized as OFET materials.

[1] Q. Meng, H. Dong, W. Hu, D. Zhua, J. Mater. Chem. 21, 11708 (2011).

[2] H. Chen, Q. Cui, G. Yu, Y. Guo, J. Huang, M. Zhu, X. Guo, Y. Liu, J. Phys. Chem. C 115, 23984 (2011).

[3] T. Mathis, Y. Liu, L. Ai, Z. Ge, D. Lumpi, E. Horkel, B. Holzer, J. Froehlich, B. Batlogg, J. Appl. Phys.

115, 043707 (2014).

[4] Y. Liu, Z. Liu, H. Luo, X. Xie, L. Ai, Z. Ge, G. Yu, Y. Liu, J. Mater. Chem. C 2, 8804 (2014).

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::i -e (1)

hv = 21.22 eV

-4

$ = oo

$ = +41 °

PFP(102) (_i)

' PFP(002) ::j)

. .. - . . .

Z C r i --------;1Y

emission angle 8

20°

o·

-3 -2 -1 0 Binding energy I eV

Valence band dispersion of epitaxial perfluoropentacene on pentacene single crystals

Yasuo Nakayama1, Ryohei Tsuruta1, Naoki Moriya1, Masataka Hikasa1, Matthias Meissner2,

Takuma Yamaguchi2, Yuta Mizuno3, Toshiyasu Suzuki2, Tomoyuki Koganezawa4, Takuya Hosokai5,

Takahiro Ueba2, Satoshi Kera2,3

1Department of Pure and Applied Chemistry, Tokyo University of Science, Noda (Japan) 2Institute for Molecular Science, National Institutes of Natural Sciences, Okazaki (Japan)

3Graduate School of Advanced Integration Science, Chiba University, Chiba (Japan) 4Japan Synchrotron Radiation Research Institute (JASRI), SPring-8, Sayo (Japan)

5National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba (Japan)

Delocalization of charge carriers is a key requirement for pursuit of efficient organic electronics as

this leads to a increase in magnitude for charge carrier mobility through realization of the ‘’band

transport’’. Highly ordered molecular assembly is a necessary condition for the formation of

delocalized electronic bands. Hence, in the cases of organic optoelectronic devices with embedded

donor-acceptor (p-n) heterojunctions, molecular heteroepitaxy potentially opens one promising

possibility for the development of high-mobility devices. In fact, our group has unveiled that n-type

C60 molecules epitaxially assemble into sub-micrometer-wide crystallites on the single crystal

surfaces of p-type pentacene [1-3] or rubrene [4]. In

the present study, perfluoropentacene (PFP, C22F14)

was also revealed to form epitaxial overlayers on the

pentacene (C22H14) single crystals (Pn-SCs) to construct

a highly ordered organic ‘’complementary’’ p-n

heterojunction. Precise crystallographic structures at

the interface and the valence band dispersion were

demonstrated by means of grazing-incidence X-ray

diffraction (GIXD) and angle-resolved ultraviolet

photoelectron spectroscopy (ARUPS), respectively.

Figure 1 shows two-dimensional GIXD patterns

of a Pn-SC sample covered with PFP. The orientation of

the PFP lattice with respect to that of the Pn-SC

surface is uniquely determined from the sample

azimuthal angles where the PFP-derived diffraction

spots appeared. Figure 2 shows ARUPS spectra of the

epitaxial PFP on Pn-SC. Peaks attributed to the HOMO

of PFP exhibited clear variation depending on the

photoelectron emission angle θ, demonstrating the

existence of the energy dispersion of the valence

bands. As widely-dispersed valence bands was proven

also for the Pn-SC substrate [5,6], the present results

suggest that the charge carriers can delocalize on both

side of this donor-acceptor molecular interface.

[1] Y. Nakayama, et al., ACS Appl. Mater. Interf. 8,

13499. (2016) [2] R. Tsuruta, et al., J. Cryst. Growth

468, 770. (2017) [3] Y. Nakayama, et al., Adv. Mater.

Interf. 5, 1800084. (2018) [4] R. Tsuruta, et al., J. Phys.:

Cond. Matter 31, in press. (2019) [5] Y. Nakayama, et

al., J. Phys. Chem. Lett. 8, 1259. (2017) [6] Y. Nakayama,

et al., J. Mater. Res. 33, 3362. (2018)

Fig. 1: 2D-GIXD patterns of a Pn-SC sample covered with 20 nm-thick PFP taken at two different in-plane azimuthal angles φ.

Fig. 2: ARUPS spectra of a 4 nm-thick PFP on Pn-SC. The measured direction in the surface Brillouin zone of PFP is indicated in the inset.

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Bio-degradable conjugated polymer particles as bio-medical imaging probes -mandatory blank line-Alexander J.C. Kuehne -mandatory blank line-

Institute of Macromolecular and Organic Chemistry, Ulm University, Ulm (Germany)

-mandatory blank line-Conjugated polymer particles represent high potential imaging probes for biomedical analysis and diagnosis due to their high contrast in fluorescence and photoacoustic tomography and their low cytotoxicity. Furthermore, conjugated polymer particles are practically non-bleaching, they can be tuned in their resonance frequency depending on the respective imaging modality and the can be functionalized with biological recognition motifs for specific targeting towards pathological tissue. However, conjugated particles are not biodegradable, which prevents their clinical application as the particles would accumulate in the body and cause undesired side effects. I will present the synthesis of highly fluorescent particles, which consist of fully π-conjugated imidazole copolymers. The imidazole can be oxidized, which leads to degradation of the conjugated polymer particles into small water soluble molecules.[1] I will show that this oxidative degradation can be performed by activated macrophages, immune cells which collect foreign particles in the body. The particles can be surface functionalized using simple click chemistry allowing targeting of cells specifically. The small degradation products are small enough to be excreted renally, making this approach a first step towards clinical applications of conjugated polymer particles as theranostic probes. Futhermore, biodegradable conjugated polymer are interesting for other applications in transient organic electronics and optoelectronics at the biointerface.

[1] T. Repenko, A. Rix, S. Ludwanowski, D. Go, F. Kiessling, W. Lederle, and A. J. C. Kuehne, Nat.

Commun. 8, 470. (2017)

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Synthesis and Properties of Molecular Spoked Wheels

Sigurd Höger1

1Kekulé‐Institut für Organische Chemie und Biochemie, Rheinische Friedrich‐Wilhelms‐Universität,

Bonn (Germany)

Rigid conjugated macrocycles are available by oxidative acetylene coupling leading to butadiynylene units in the ring or by Yamamoto coupling leading to pure phenylene rings. However, the shape‐persistence of these macrocycles is limited due to the finite persistent length of the underlying constitutional building blocks. More rigid circular objects are so‐called molecular spoked wheels, where conjugated spokes inside the macrocycle stiffen the object [1, 2]. Connecting the spoke‐rim segments to a central hub and subsequent rim formation leads to wheels with a diameter of up to 10 nm [3]. Apart from defined structure and conformation, spoked wheels self‐assemble at the surface of HOPG to form extended 2D‐structures. Moreover, they exhibit interesting optical properties as determined by single molecule spectroscopy [4].

[1] D. Mössinger, D. Chaudhuri, T. Kudernac, S. Lei, S. De Feyter, J.M. Lupton, S. Höger, J. Am. Chem. Soc. 132, 1410 (2010). [2] A. Idelson, C. Sterzenbach, S.‐S. Jester, C. Tschierske, U. Baumeister, S. Höger, J. Am. Chem. Soc. 129, 1254 (2017). [3] R. May, S.‐S. Jester, S. Höger, J. Am. Chem. Soc. 136, 16732 (2014). [4] V. Aggarwal, A. Thiessen, A. Idelson, D. Kalle, D. Würsch, T. Stangl, F. Steiner, S.‐S. Jester, J. Vogelsang, S. Höger, J. M. Lupton, Nat. Chem. 5, 964 (2013).

+

r= h+ I

e-

l Substrate

~ ·2 ::,

a)

-€ Spiro+ PVBl :TFSI ' ~

~ C ::,

8 Spiro

3.5 4.5 Kinetic Energy (eV)

5.5 3 2 1 0 -1 Binding Energy (eV)

Tuning the Interfacial Electronic Properties for High-Performance Perovskite Solar Cells

Anirudh Sharma,1 Camille Geffroy,1 Samy Almosni,2 Fumiyasu Awai,2 Takeru Bessho,2 Eric Cloutet,1

Thierry Toupance,3 Hiroshi Segawa,2 Georges Hadziioannou.1

1Laboratoire de Chimie des Polymères Organiques (LCPO), University of Bordeaux, Pessac (France) 2Research Center for Advanced Science and Technology, University of Tokyo, Tokyo (Japan)

3Institut des Sciences Moléculaires, University of Bordeaux, Talence (France)

The emergence of perovskite solar cells (PSC) and the tremendous research efforts [1] in this field has led

to PSCs with power conversion efficiencies (PCEs) of over 22%. [2] This progress is largely attributed to

the development of new perovskite material design and that of charge transport layers (CTLs). While the

high PCEs of PSCs bring them a step closer to commercialization, high cost and poor air-stability of these

devices need urgent attention to make this technology commercially viable. CTLs and their electronic

properties play a significant role in not only facilitating charge extraction but also in determining the

stability of PSCs. [3, 4]

In this work, we use photoelectron spectroscopy to elucidate the interfacial properties of hole transport

layer (HTL)-perovskite interfaces. An ionic liquid polymer poly(1-butyl-3-vinylimidazolium

bis(trifluoromethylsulfonyl)imide) (PVBI-TFSI) is demonstrated as a promising substitute for LiTFSI, which

is commonly used as a dopant for Spiro-OMeTAD. PVBI:TFSI was found to successfully p-dope Spiro-

OMeTAD and tune its electronic properties. Unlike LiTFSI, p-doping of Spiro-OMeTAD using PVBI:TFSI was

achieved without air exposure, enabling controlled fabrication of PSC devices which outperformed their

LiTFSI counterparts.

Lastly, an easy to synthesize poly(9-vinylcarbazole) (PVK) based hole transport material is presented as a

substitute for Spiro-OMeTAD. Electronic properties of the PVK based HTL-perovskite interfaces will also

be discussed.

Figure 1: (left) Schematic representation of a PSC device structure and (right) UPS spectra showing the

changes in the electronic properties of Sprio-OMeTAD when doped with PVBI:TFSI.

1. Y. Chen, L. Zhang, Y. Zhang, H. gao, and H. Yan, RSC Adv. 8, 10489. (2018) 2. W. S. Yang, B. W. Park, E. H. Jung, N. J. Jeon, Y.C. Kim, d. U. Lee,, S. S. shin, J. seo, E. K. Kim, J. H. Noh,

and S. I. Seok, Science. 356, 1376. (2017) 3. S. Wang, T. Sakurai, w. Wen, and Y. Qi, Adv. Mater. Interfaces. 1800260. (2018) 4. Z. Hawash, L. K. Ono, Y. Qi, Adv. Mater. Interfaces 5, 1700623. (2018)

Dielectric constant tuning of organic photovoltaic materials

Paul Burn, Hui Jin, Aaron Raynor

Centre for Organic Photonics & Electronics, The University of Queensland, Brisbane (Australia)

Photocurrent generation in organic photovoltaic (OPV) devices is driven by the creation and

subsequent separation of excitons into free electrons and holes. Materials with low exciton binding

energies are able to efficiently separate into free charge carriers and limit recombination pathways.

The binding energy of an exciton is dependent on a number of factors, including being proportional to

the inverse square of the dielectric constant. Additionally, according to the Clausius-Mossotti relation,

the dielectric constant of a material can be related to its density, with increased density providing a

higher dielectric constant. As a result, it is expected that increasing the dielectric constant of a material

will enhance the exciton dissociation rate, and improve OPV performance.

At present, there have been limited studies on how to increase the dielectric constant of organic

semiconductors. However recent work has shown that the inclusion of triethylene glycol monomethyl

ether chains can dramatically increase the dielectric constant at low frequency, while maintaining both

the optical and electronic properties of their alkylated derivatives. Additionally, it has been shown

that the inclusion of glycolated units has the ability to increase the molecular packing density of the

film, enhancing the high (optical) frequency dielectric constant.

Based on these considerations, this presentation will describe a family of glycolated materials that

have been engineered with the aim of increasing the dielectric constant to decrease exciton binding

energy. Additional considerations such as broad absorption within the visible light spectrum, solution

processability, and engineered energy levels will be discussed. Finally, the applicability of dielectric

constant manipulation will be reported in the context of homojunction OPV device fabrication and

performance.

Aza-Fused n-Conjugated Framework that Catalyzes the Production of Hydrogen Peroxide

Uracil grafted imine-based covalent organic framework for nucleobase recognition

Acs Cata/. 2017, 7, 1015 Chem. Commun. 54, 8729 (2018)

r~ .. :r~~ ~ ~

Thiol Grafted lmine-Based Covalent Organic Framework for Water Remediation Through Selective Removal of Hg(II) J. Mater. Chem. A, 2017,5, 17973-17981

1 Development of Novel Covalent Organic Frameworks

2

3 J.L. Segura,1

S. Royuela,1,3

A. de la Peña, 1

M.J. Mancheño,1

M. Alonso,1,3

P. García Arroyo,1

F. Zamora,2

4 C. Seoane, 1

M.M. Ramos3

5

6 1Dept. of Organic Chemistry. Faculty of Chemistry, Complutense Univ. of Madrid, 28040 Madrid

7 (Spain). Email: segura@ucm.es

8 2 Dept of Inorganic Chemistry. Faculty of Sciences, Autonoma Univ. of Madrid, 28049 Madrid (Spain).

9 3Chemical and Environmental Technology Department. Univ. Rey Juan Carlos, 28933 Madrid (Spain)

10

11 Covalent organic frameworks (COFs) comprise an emerging class of materials based on the atomically

12 precise organization of organic subunits into two- or three-dimensional porous crystalline structures

13 connected by strong covalent bonds with predictable control over composition, topology and

14 porosity.[1] They offer an efficient strategy of controlling the covalent bond beyond molecules and

15 demonstrate how this control results in expansion of the scope of covalent organic solids and their

16 properties.

17 Although they have been first explored for applications related with gas adsorption and

18 storage, the suitable incorporation of new functional building blocks has opened up new

19 potential uses as advanced materials. The aim of this communication is to show selected

20 examples of applications based on COFs synthesized in our research group including among

21 others (i) water remediation through selective removal of Hg/II), (ii) selective nucleobase

22 recognition or (iii) the electrocatalytic production of hydrogen peroxide.

23

24 [1] Segura, J.L.; Mancheno, M.J.; Zamora, F. Covalent organic frameworks based on Schiff-base

25 chemistry: Synthesis, properties and potential applications. Chem. Soc. Rev. 2016, 45, 5635–5671.

4.0 • • ~ 3.5 - ... 8 3.0 • <=1 a 2_5 ~ 2.0 "' 1.5

0 .!:;<LO ~ 0.5 •

0.0 0.00 0.10 0.20 0.30 0.50

Hole Reorganization Energy (eV)

Massive theoretical design of hole conducting organic materials by using cloud computing

environment

Nobuyuki N. Matsuzawa1, Hideyuki Arai

1, Masaru Sasago

1, Eiji Fujii

1, Alexander Goldberg

2,

Thomas J. Mustard2, H. Shaun Kwak

2, David J. Giesen

2, James Watney

2, Fabio Ranalli

2, Volker Eyrich

2,

Mathew D. Halls2

1Engineering Division, Automotive & Industrial Systems Company, Panasonic Corp., Osaka, Japan.

2Schröodinger Inc., San Diego, CA, USA.

Materials exhibiting higher mobilities than conventional organic semiconducting materials such as

fullerenes and fused thiophenes are in high demand for applications such as printed electronics. For

hole conducting materials, derivatives of [1]benzothieno[3,2-b][1]benzothiophene (BTBT) are known

to exhibit the highest hole mobility [1], yet their carrier transfer performance is still not satisfactory.

In order to discover new molecules in the benzothiophene family that might show improved charge

mobility, a massive theoretical screen of hole conducting properties of molecules was performed by

using cloud computing environment. Over 7,000,000 structures of fused furans, thiophenes and

selenophenes were generated and 250,000 structures were randomly selected to perform DFT

(Density Functional Theory) calculations of hole reorganization energies and dipole moments.

Calculated dipole moments are plotted against calculated reorganization energies in Fig. 1. Among

the 250,000 compounds, we chose 130 compounds as exemplary candidates, whose hole

reorganization energies were lower than others. Finally we calculated hole mobilities of the 130

compounds in the amorphous state by combining molecular dynamics simulations with quantum

chemical calculations. The amorphous phase of candidate molecules was obtained by applying

molecular dynamics calculations using the program Desmond [2], and transfer integrals were

calculated for pairs of molecules in the obtained amorphous state using the DFT program Jaguar [3].

Marcus theory in combination with the percolation treatment as derived by Evans et al. [4] was then

applied to obtain estimated carrier mobilities of molecules. In total, more than 3,000,000 DFT

calculations were performed by using the cloud computing environment with gross total time being

only 16 days. New candidate molecules having fused selenophene structure were extracted that

might show higher mobilities than conventional BTBT derivatives. Further details will be presented

on directions of improvement of mobilities for the fused aromatic molecules with hetero atoms.

[1] K. Takimiya, I. Osaka, T. Mori, M. Nakano, Acc. Chem. Res. 47, 1493. (2014).

[2] K. J. Bowers, E. Chow, H. Xu, R. O. Dror, M. P. Eastwood, B. A. Gregersen, J. L. Klepeis, I. Kolossvary,

M. A. Moraes, F. D. Sacerdoti, J. K. Salmon, Y. Shan, D. E. Shaw, Proc. 2006 ACM/IEEE Conf. on

Supercomputing, 84. (2006).

[3] A. D. Bochevarov, E. Harder, T. F. Hughes, J. R. Greenwood, D. A. Braden, D. M. Philipp, D. Rinaldo,

M. D. Halls, J. Zhang, R. A. Friesner, Int. J. Quantum Chem. 113, 2110. (2013).

[4] D. R. Evans, H. S. Kwak, D. J. Giesen, A. Goldberg, M. D. Halls, M. Oh-e, Org. Electronics, 26, 50.

(2016).

Fig. 1. Calculated hole reorganization energy and dipole moment for the 250,000 compounds.

0.2

·0.7 IE

Side Chain

0.2 0.4 0 .6 0.8

Potential vs Ag/Ag· M

g 0.75

~ ""'- ~ o~ d j o.so

~ ·· 0 0 y 08

000

1 DisentanglingRedoxPropertiesandCapacitanceinSolubleConjugatedPolymers for 2 ElectrochemicalandBioelectronicApplications 3 4 Anna M. Österholm1,Lisa R. Savagian2, James F. Ponder Jr.1,3, John. R. Reynolds1,2

5 6 1

School of Chemistry and Biochemistry, 2School of Materials Science and Engineering, 7 Georgia Institute of Technology, Atlanta (USA) 8 3

Department of Chemistry, Imperial College, London (UK) 9

10 11 The ability to effectively transport both ions and electrons, have made conjugated polymers attractive 12 candidates for a range of redox active devices such as biosensors and ion pumps, electrochemical 13 transistors, energy storage and conversion, and electrochromic displays, to name a few. The recent 14 revival of organic bioelectronics, in particular, has demonstrated that there needs to be a better 15 understanding of mixed ion and electron transport in these materials. By using a backbone motif where 16 the solubilizing groups are not directly attached to the conjugated backbone, we demonstrate how 17 numerous redox properties, including onset of oxidation, capacitance, and conductance profile, of 18 dioxythiophene-based copolymers can be manipulated by changing the nature of the solubilizing 19 groups (Figure 1, top & bottom left). [1] We also show how a range of readily accessible 20 electrochemical and spectroscopic techniques can offer a great deal of insight into trends and acquire 21 a better understanding of the ion and charge transport in materials that do not have the necessary 22 long range order to be characterized using X-ray techniques. Finally, we will demonstrate how 23 functionalizing the same dioxythiophene backbone with oligoether chains affords a material that is 24 highly electroactive in aqueous electrolytes (Figure 1, top right), allowing it to be seamlessly integrated 25 into high-performing electrochemical transistors with competitive on/off current ratios and high 26 gravimetric capacitance (Figure 1, bottom right).[2] By using a propylenedioxythiophene backbone, 27 the presented copolymers can be synthesized using direct arylation polymerization, to afford polymers 28 with high solubility and molecular weights allowing them to be solution-processed into homogeneous 29 electroactive films at room temperature.

30 31 32 33 Figure 1. Varying the side 34 chains to control onset of 35 oxidation (top left) and 36 potential dependent 37 conductance (bottom left). 38 Oligoether side chains afford 39 reversible redox switching in 40 salt water and accumulation 41 mode OECTs with competitive 42 mobility, high volumetric 43 capacitance, moderate 44 transconductance, as well as 45 an ION/OFF current ratio of 105. 46

47 48 [1] A. M. Österholm, J. F. Ponder Jr., M De Keersmaecker, D. E. Shen, J. R. Reynolds, submitted 49 [2] L. R. Savavian, A. M. Österholm, J. F. Ponder Jr., K. J. Barth, J. Rivnay, J. R. Reynolds, Adv. Mater. 30, 50 1804647. (2018)

.. . ~···· tTIPS

N N 1- '< .- .-1

$

TIPS TIPS TIPS

1 The 2D and 3D extension of long pyrene-fused N-heteroacenes

2 -mandatory blank line-

3 Benlin Hu1, Martin Baumgarten

1

4 -mandatory blank line-

5 1Max Planck Institute for Polymer Research, Ackermannweg 10, D-55128, Germany

6 -mandatory blank line-

7 We designed and synthesized 2D and 3D thiadiazoloquinoxaline containing long N-Nanorribbons with

8 a size approaching 11 nm. Crystal structure analysis demonstrated in-plane extension through close

9 contacts of thiadiazoles and layered packing enabling in-plane and interlayer electron transport.

10 Organic field-effect transistor devices provided electron mobilities, which supply a potential way to

11 enhance the charge transport in long N-heteroacenes.

12

13 14

15 References:

16 [1]. B. Kohl, F. Rominger, M. Mastalerz, Angew. Chem. Int. Ed. 2015, 54, 6051-6056

17 [2]. B.-L. Hu, K. Zhang, C. An, D. Schollmeyer, W. Pisula, M. Baumgarten. Angew. Chem. Int. Ed. 2018,

18 57, 12375-12379.

19 [3]. B.-L. Hu, K. Zhang, C. An, W. Pisula, M. Baumgarten, Org. Lett. 2017, 19, 6300-6303.

20 [4]. D. Cortizo-Lacalle, J. P. Mora-Fuentes, K. Strutynski, A. Saeki, M. Melle-Franco, A. Mateo-Alonso,

21 Angew. Chem. Int. Ed. 2018, 57, 703-708.

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Thermally Activated Delayed Fluorescence vs Room Temperature Phosphorescence how to

control opposite processes in the same molecule and use in OLEDs

-mandatory blank line-Przemyslaw Data1,2,3, Heather Cole3, Youhei Takeda4

-mandatory blank line-1Department of Physical Chemistry and Technology of Polymers, Silesian University of Technology,

Gliwice (Poland) 2Centre of Polymer and Carbon Materials, Polish Academy of Sciences, Zabrze (Poland)

3Department of Physica, Durham University, Durham, (United Kingdom) 4Department of Applied Chemistry, Osaka University, Osaka (Japan)

-mandatory blank line-The discovery of electroluminescence of organic molecules is one of the ground-breaking and promising breakthroughs in the last century. Owing to it and to the progress in the field of organic electronics over the last half-century, nowadays, we are surrounded by organic light-emitting diodes (OLEDs) products. In addition to lightness, flexibility, and low production cost, the major advantage of using organic emitters for OLEDs is the possibility to tailor their properties by designing and modifying their molecular structures. From the viewpoint of emission mechanisms, there are two types of emitters: fluorescence and phosphorescence emitters. Fluorescence emitters are the first generation of electroluminescence emitters for OLEDs, but they are fatally restricted by the upper limit of internal quantum efficiency (IQE) of 25%, due to spin statistics. The second generation emitter, phosphorescence emitters, are more efficient and for this reason, are commonly used in OLED-based displays. However, nothing is perfect: phosphorescence emitters that are currently used in organic electronics are organometallic complexes comprising of very expensive and rare heavy metals such as Ir and Pt. To overcome this problem, the search for all-organic TADF (Thermally Activated Delayed Fluorescence) and RTP (Room Temperature Phosphorescence) emitters is conducted. Herein we present a new approach to the design of metal-free organic thermally activated delayed fluorescence and room temperature phosphorescence emitters for organic light-emitting diodes. The subtle tuning of the energy difference between the singlet and triplet excited states allows for tailored emission properties and switching of emission channels between thermally activated delayed fluorescence and room temperature phosphorescence. Moreover, we have realized an efficient and heavy atom-free room temperature phosphorescence organic light-emitting diodes using the developed emitter.

Acknowledgement P.D. kindly acknowledges the support received from the First Team program of the Foundation for Polish Science co-financed by the European Union under the European Regional Development Fund, project no. First TEAM 2017-4/32.

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1 Microstructure and sequence of conjugated polymers revealed by 2 high-resolution scanning probe microscopy 3 4 Giovanni Costantini

6 Department of Chemistry, University of Warwick, Coventry, CV4 7AL, UK 7 8 9

The structure of a conjugated polymer and its solid-state assembly are without a doubt the most 11 important parameters determining its properties and performance in (opto)-electronic devices. A 12 huge amount of research has been dedicated to tuning and understanding these parameters and 13 their implications in the basic photophysics and charge transporting behaviour. The lack of reliable 14 high-resolution analytical techniques constitutes however a major limitation, as it hampers a better

understanding of both the polymerisation process and the formation of the functional thin films used 16 in devices. 17 Here, by combining vacuum electrospray deposition and high-resolution scanning tunnelling 18 microscopy (STM) we demonstrate the ability of imaging conjugated polymers with unprecedented 19 detail, thereby unravelling structural and self-assembly characteristics that have so far been

impossible to determine. 21 Applying this novel technique to prototypical conjugated polymers, we show that sub-molecular 22 resolution STM images allow us to precisely identify the monomer units and the solubilising alkyl 23 side-chains in individual polymer strands. Based on this, it becomes possible to determine the 24 molecular number distribution of the polymer by simply counting the repeat units. More

importantly, we demonstrate that we can precisely determine the 26 nature, locate the position, and ascertain the number of defects in 27 the polymer backbone [1]. This unique insight into the structure of 28 conjugated polymers is not attainable by any other existing 29 analytical technique and represents a fundamental contribution to

the long-discussed issue of defects as a possible source of trap 31 sites. Furthermore, the analysis of our high-resolution images 32 univocally demonstrates that one of the main drivers for backbone 33 conformation and polymer self-assembly is the maximization of 34 alkyl side-chain interdigitation. On this basis, we investigate the 2D

assembly of a series of conjugated polymers with varying backbone 36 chemical compositions to explore the range of applicability of a 37 simple model for linear alkyl side-chain interdigitation based on 38 the maximisation of van der Waals interactions [2]. 39

41 [1] D.A. Warr, L.M.A. Perdigão, H. Pinfold, J. Blohm, D. Stringer, A. Leventis, H. Bronstein, A. Troisi, 42 G. Costantini, Sci. Adv. 4, eaas9543 (2018). 43 [2] D.A. Warr, et al., in preparation. 44

46 47 48 49

High resolution STM image of poly(C14DPPF-F) on Au(111).

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Thiophene-based S,N-Heteroacenes: Electronic Properties and X-Ray Structure Analysis

E. Mena-Osteritz, P. Bäuerle

Institute of Organic Chemistry II and Advanced Material, Ulm University,Ulm (Germany)

Thiophene-based S,N-heteroacenes have been synthesized recently [1] and attracted strong interest in the field of organic electronics as key-component semiconductors.[2-3] The versatility of such organic molecules to form novel stable topological conjugates opens a broad, highly interesting spectrum of electronic and photophysical properties to be studied.

In this contribution, the photophysical behavior of series of linear S,N- and Se,N-heteroacenes showing a planar π-delocalized system will be discussed. With the help of theoretical calculations the electronic properties of those systems will be correlated with experimental findings.

Furthermore, X-Ray structure analysis on brand new three-dimensional thienylene-phenylene structures and their electronic properties will be presented.

[1] C. Wetzel, E. Brier, A. Vogt, A. Mishra, E. Mena-Osteritz, and P. Bäuerle, Angew. Chem. Int. Ed. 54, 12334 (2015). [2] C. Wetzel, A. Vogt, A. Rudnick, E. Mena-Osteritz, A. Köhler, and P. Bäuerle, Org. Chem. Front. 4, 1629-1635 (2017). [3] T. Leitner, A. Vogt, D. Popović, E. Mena-Osteritz, K. Walzer, M. Pfeiffer, and P. Bäuerle, Mater.

Chem. Front., 2, 959-968 (2018).

Molecular modeling of hybrid sp-sp2 carbon-based nanostructures: structural, electronic and vibrational properties

Patrick Serafni1, Alberto Milani1, Matteo Tommasini2, Chiara Castiglioni2, Carlo E. Bottani1

and Carlo S. Casari1

1Dipartimento di Energia, Politecnico di Milano,via Ponzio 34/3, Milano, Italy 2Dipartimento di Chimica, Materiali e Ing. Chimica, Politecnico di Milano, P.zza L. da Vinci

32, Milano, Italy

1D carbon atom wires (CAWs) and hybrid sp-sp2 carbon 2D structures, such as graphynes (GY) and graphdiynes (GDY), are polyconjugated materials that show very peculiar properties and are gathering more and more interest in materials science. CAWs are fnite-length monoatomic chains of sp-hybridized carbon atoms, while the second are 2D crystals, similar to graphene, in which phenyl rings are connected through monoacetylenic (GY) or diacetylenic (GDY) units. The electronic and optical properties of these systems are strongly dependent on their structure, that can be properly designed to obtain an insulating, semiconducting or metallic behavior [1,2]. To what extent these properties can be tuned by controlling π-electron conjugation and by modulating both intramolecular and intermolecular interactions is still an open issue. In this work, molecular modeling is adopted to investigate the electronic and vibrational properties of diferent CAWs and hybrid sp-sp2 carbon-based nanostructures. By means of Density Functional Theory, the efect of diferent end-groups in driving the semiconductor-to-metal transition is investigated on a series of CAWs: through an analysis of the HOMO-LUMO gap and of the Raman response, calculations reveal that the increase of conjugation alone is not enough to endow a full tunability of properties, that can be obtained instead by controlling charge transfer or by proper chemical design [3,4].The same analysis is then extended to the computational investigation of γ-graphdiyne (γ-GDY): by using a bottom-up approach, molecular models of increasing size and complexity are employed to investigate the efect of topology and of the chemical connectivity on the band gap. These results are compared with the gap of infnite 1D polymers and 2D GDY, as computed by DFT calculations in periodic boundary conditions carried out with CRYSTAL code. The analysis of confnement efects is then completed by analyzing the band structure of γ-graphdiyne nanoribbons, shedding light on the efect of the diferent edges on both the band gap and the Raman response. These results provide guidelines for the interpretation and characterization of the peculiar physicochemical efects occurring in CAWs-based or GDY-based materials, but also for the molecular design of novel sp−sp2 carbon nanostructures, where the capability to tune the response is appealing for an all-carbon-based science and technology.

[1] C.S. Casari, M. Tommasini, R. R. Tykwinski and A. Milani Nanoscale 8, 4414, 2016.[2] C.S Casari, A. Milani MRS Comm. 8, 207, 2018.[3] Alberto Milani, Matteo Tommasini, Valentino Barbieri, Andrea Lucotti, Valeria Russo, Franco Cataldo and Carlo S. Casari J. Phys. Chem.C 121, 10562, 2017. [4] A. Milani et al. Sci. Rep. 2019, in press.

Transistors of charge-transfer complexes

T. Mori1, R. Sato1, R. Sanada1, K. Iijima1, D. Yoo1, and T. Kawamoto1

1Tokyo Institute of Technology, Department of Materials Science and Engineering, Tokyo, Japan. E-mail: mori.t.ae@m.titech.ac.jp

Recently, charge-transfer complexes composed of donor (D) and accepter (A) molecules have been investigated extensively in order to study the doping effect [1], as well as to study conduction mechanism of high-performance DA polymers using well-defined analogous systems. Along this line, we have investigated transistors of mixed-stack charge-transfer complexes. Though these complexes contain both D and A units, they usually show only n-type characteristics. This is because the D HOMO and the A LUMO are orthogonal, and the D next HOMO mediates the electron transport [2,3]. Unoccupied orbitals and the A orbitals below HOMO do not work as bridge orbitals respectively due to the many-node structures and due to the deep energy levels, so that pure hole transport is never attained in DA cocrystals. If the D HOMO and the A LUMO are not orthogonal, ambipolar transport is expected, but we demonstrate several examples in which contributions of second bridge orbitals lead to practically monopolar transport. In (perylene)(DBrDCNQI), hole-dominant ambipolar transport is observed (Fig. 1(a)) because the second bridge orbital (HOMO−4) reduces the electron transport (Fig. 1(b)). In 1,5-dibromo-2,6-naphthoquinhydrone, the D HOMO and the A LUMO are practically the same, but the second bridge orbital (HOMO−1) enhances the electron transport but cancels the hole transport (Fig. 1(d)). Accordingly, only electron transport is observed (Fig. 1(c)) [4].

References [1] I. Salzmann, Acc. Chem. Res. 2016, 49, 370. [2] K. Iijima, ACS Adv. Mater. Interface 2018, 30, 10262. [3] R. Sato, J. Mater. Chem. C doi: 10.1039/c8tc05190a. [4] R. Sato, Chem. Lett. 2019, 48, .

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1 Efficient “Sensitized” Ternary Polymer Solar Cells with Small Photon Energy Loss

2 -mandatory blank line-

3 Itaru Osaka,1 Masahiko Saito,1 Yasunari Tamai,2 Hideo Ohkita,2 Hiroyuki Ichikawa,3 Hiroyuki Yoshida3

4 -mandatory blank line-

5 1Department of Applied Chemistry, Graduate School of Engineering, Hiroshima University, Higashi-

6 Hiroshima (Japan)

7 2Department of Polymer Chemistry, Graduate School of Engineering, Kyoto University, Kyoto (Japan)

8 3Graduate School of Engineering, Chiba University, Chiba (Japan)

9 -mandatory blank line-

10 Significant improvement of the power conversion efficiency has been made in polymer-based

11 solar cells. Ternary blend cells, in which three organic semiconductors are blended to efficiently

12 absorb broad range of the incident light, have shown to be an excellent strategy for improving the

13 efficiency. Here, we show that a ternary system composed of a thaizolothiazole-thiophene polymer

14 (PTzBT, Figure 1) [1], with a relatively wide bandgap of 1.85 eV, and PCBM along with a very small

15 amount (ca. 6 wt%) of a non-fullerene acceptor (ITIC, Figure 1), with a narrower bandgap of 1.6 eV,

16 as the third component greatly improved the efficiency up to 10.3% compared to that of the

17 PTzBT:PCBM binary system (7.5%). The optimal active layer thickness of the PTzBT:PCBM:ITIC ternary

18 blend cells was as thick as 370 nm. Interestingly, although this ternary blend system included only 6

19 wt% of ITIC, the external quantum efficiency at the ITIC absorption was as high as that at the polymer

20 absorption. More importantly, the ternary system had a VOC similar to the binary system, due to the

21 well cascaded frontier energy levels, while it had an extended absorption range, resulting in the

22 significantly reduced photon energy loss/voltage loss. We believe that the sensitized ternary system

23 is a promising approach for improving the efficiency of polymer solar cells.

24

PTzBT ITIC25 26 Figure 1. Chemical structures of PTzBT and ITIC

27

28 [1] I. Osaka, M. Saito, T. Koganezawa, K. Takimiya, Adv. Mater. 26, 331 (2014).

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Liquid crystallinity as a self-assembly motif for solid state singlet fission materials

Saghar Masoomi-Godarzi,1 Maning Liu,3 Yasuhiro Tachibana,3 Valerie D. Mitchell,1 Lars Goerigk,2

Kenneth P. Ghiggino,2 Trevor A. Smith2 and David J. Jones1

1School of Chemistry/Bio21 Institute, University of Melbourne, Melbourne (Australia) 2School of Chemistry, University of Melbourne, Melbourne (Australia)

3School of Engineering, RMIT University, Bundoora (Australia)

S1 1(TT) 2xT1

Multiple exciton generation (MEG) through singlet fission (SF) is a spin allowed process whereby a

singlet excited state is split into two triplet excitons. Inclusion of MEG chromophores into solar cells

raises the maximum theoretical efficiency of a solar cell from the Schockly-Queisser Limit of 33% to

around 45% by effectively harvesting the energy from high energy photons. SF has been reported

and extensively studied in crystalline acenes, and more recently acene dimers to better understand

the fundamental photophysics and materials requirements for SF. Incorporation of these SF materials

in to functional solar cells, although demonstrating modest efficiency enhancements, has had limited

success. In our efforts to produce higher efficiency printed organic solar cells we had the desire to

incorporate solution processible SF materials in printed organic solar cells, however most of the

reported SF materials are highly crystalline and either do not promote SF in the solid state or

controlling crystallisation is difficult.

Here we report our studies of new solid-state singlet fission materials using liquid crystallinity to

promote self-assembly and to pre-organise triplet host chromophores. Using design criteria outlined

by Busby et al. [1], suggesting an Acceptor-Donor-Acceptor (A-D-A) structure may support SF, we

have used strong p-p interactions of a fluorenyl-substituted hexabenzocoronene (FHBC) donor to

promote strong self-assembly, coupled with thienyl-substituted diketopyrrolopyrrole (TDPP) as the

triplet host. We needed to design our intra-molecular SF host, with i) a singlet energy around 2.0 eV

if TDPP was to be our triplet host, ii) strong self-association through the core, and iii) solution

processability. Thin films of the discotic liquid crystalline FHBC(TDPP)2 material forms hexagonally

packed columns and has a singlet energy level of 2.00 eV [2]. SF studies on FHBC(TDPP)2 demonstrate

a triplet yield of 150% in amorphous thin films, increasing to 170% in thermally annealed films.[3]

This constitutes a new class of singlet fission materials.

[1] Busby, E.; Xia, J.; Wu, Q.; Low, J. Z.; Song, R.; Miller, J. R.; Zhu, X. Y.; Campos, L. M.; Sfeir, M. Y Nat.

Mater., 14, 426-33. (2015)

[2] Wong, W. W. H.; Subbiah, J.; Puniredd, S. R.; Purushothaman, B.; Pisula, W.; Kirby, N.; Muellen, K.;

Jones, D. J.; Holmes, A. B., J. Mater. Chem. 22 (39), 21131-21137. (2012)

[3] Saghar Masoomi-Godarzi, Maning Liu, Yasuhiro Tachibana, Valerie D. Mitchell, Lars Goerigk,

Kenneth P. Ghiggino, Trevor A. Smith and David J. Jones submitted manuscript

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----Fabrication of reproducible and reliable organic field-effect transistors by solution-

shearing employing blended organic semiconductors

Antonio Campos, Inés Temiño, Adrian Tamayo, Sergi Riera-Galindo, Qiaoming Zhang, Raphael

Pfattner, Francesca Leonardi, Stefano Casalini, Freddy Del Pozo, Marta Mas-Torrent

Institut de Ciència de Materials de Barcelona (ICMAB-CSIC), Campus UAB, Bellaterra (Spain)

Organic-based devices are attracting great attention for applications requiring low-cost and

flexibility. Engineering processing techniques that could give rise to highly crystalline and

homogenous semiconducting films resulting in reproducibly high mobility and reliable devices is a

current challenge. We report here the bar-assisted meniscus shearing of organic semiconductor

blends based on small semiconducting molecules and an insulating polymer.[1-2] This technique

results in highly crystalline thin films that show ideal OFET characteristics. Further, we investigated

the influence of the deposition parameters and solution formulation on the thin film morphology and

polymorphism, which in turn, has a crucial impact on the device performance.[3] In particular, we

found that the use of insulating binding polymers is key to fabricate more reliable n-type OFETs

(Figure 1). The best devices have also been successfully applied in water and solid electrolyte gated

OFETs exhibiting a very high performance and great potential for the development of sensors.[5-7]

Performance

enhancement

Figure 1. Deposition by bar-assisted meniscus shearing of a PDI derivative with and without polymer binder.

[1] F. G. Del Pozo, S. Fabiano, R. Pfattner, S. Georgakopoulos, S. Galindo, X. Liu, S. Braun, M. Fahlman,

J. Veciana, C. Rovira, X. Crispin, M. Berggren, M. Mas-Torrent, Adv. Funct. Mater. 26 , 2379 (2016).

[2] I. Temiño , F.G.Del Pozo, A.Murugan, S. Galindo, J. Puigdollers, M. Mas-Torrent, Adv. Mater.

Technol. 1, 1600090 (2016).

[3] S. Galindo, A. Tamayo, F. Leonardi, M. Mas-Torrent, Adv. Funct. Mat. 27,1700526 (2017).

[4] A. Campos, S. Riera-Galindo, J. Puigdollers, M. Mas-Torrent, ACS Appl. Mater. Interfaces 10, 15952

(2018).

[5] F. Leonardi, S. Casalini, Q. Zhang, S. Galindo, D. Gutiérrez, M. Mas-Torrent, Adv. Mater. 28, 10311

(2016).

[6] Q. Zhang, F. Leonardi, S. Casalini, M. Mas-Torrent, Adv. Funct. Mater. 27, 1703899 (2017).

[7] Q. Zhang et al. submitted results.

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1 Charge Separation in Organic Solar Cells: Energy Bending versus Energy Disorder

2

3 Gjergji Sini

4

Chemistry Departement, University of Cergy-Pontoise, Cergy-Pontoise, (France)

6

7 Abstract:

8 In the domain of organic solar cells (OSC), the long-lasting dominance of fullerene-based acceptors

9 has been recently overcome. Different mechanisms that could explain this enormous boost in solar

cell efficiency have been suggested. Recent theoretical studies highlight the dominant role that the

11 energy disorder and the entropy play on the charge separation efficiency at the donor-acceptor (D-A)

12 interface. [1-2] However, implicit contributions from driving forces other than the energy disorder

13 make unclear the individual impacts of different factors. Comparative studies between the impacts of

14 each mechanism are thus still missing but highly desirable for the design of new materials.

Aiming to obtain deeper insights on the mechanisms impacting the charge separation efficiency at

16 the D-A interface, here we focus on the relative impact of two driving forces: the energy bending (EB)

17 and the energy disorder. We firstly discuss results obtained by means of density functional theory

18 (DFT) methods, allowing to (i) demonstrate the presence of a substantial driving force (EB) between

19 the donor-acceptor interface and the pure donor- and acceptor domains; (ii) identify the reasons for

this driving force (geometric deformations and direct-contact intermolecular polarization). [3] In a

21 second time, we compare the impact of the EB and of the energy disorder on the charge separation

22 efficiency by means of Kinetic Monte-Carlo (KMC) simulations. Our results suggest large impact of

23 the EB on the charge separation efficiency, which is much stronger than the effect of the energy

24 disorder. [4]

References:

26 [1] D. A. Vithanage, et al. Nature Communications, 4, 2334, (2013)

27 [2] Hood, S. et al. J. Phys. Chem. Lett. 7, 4495, (2016)

28 [3] Sini, G., et al., Adv. Energy Mater. 1702232, (2018)

29 [4] L. Sousa, V. Coropceanu, D. A. da Silva Filho, G. Sini. Manuscript in preparation

Singlet fission phenomenon: quantifying “dark” triplet states in organic semiconductors

David Rais,1 Jiří Pfleger,1 Petr Toman,1 Miroslav Menšík,1 Yaduram Panthi,1 Udit Acharya, 1 Alexander

Figure 1: Ultrafast singlet

fission in a metallo-

supramolecular polymer.

Zhigunov,1 Martin Vala,2 Jozef Krajčovič,2 Stanislav Stříteský,2 Martin Weiter2

1Institute of Macromolecular Chemistry, Czech Academy of Sciences, Prague (Czech Republic)

2Materials Research Centre, Brno University of Technology, Brno (Czech Republic)

The triplet (high-spin) excitons play an important role in photophysical processes occurring in the organic materials. It stems from the uniquely long lifetime of the triplets that is made possible by the weak spin-orbit coupling together with spin-forbidden transition to the ground state. Control of their formation and annihilation plays a key role not only in the industry to achieve high external quantum yield of electroluminescence in current commercial organic light-emitting devices [1], but also at much larger scale in the nature – e.g. for photo-protection in plants [2].

We focus on the phenomenon of singlet fission (SF), i.e. generation of a pair of triplet excitons (2T1) out of one photogenerated singlet exciton (S1) in organic semiconductors:

2S0 + hν → S0+S1 → 1(TT) → 2T1

It was envisaged as a way to increase the theoretical limit of energy conversion in solar photovoltaic cells [3], since both triplets can possibly undergo a charge separation and thus contribute the photocurrent with two charge carriers instead of only one. The main obstacle in SF phenomenon research is to distinguish it from the intersystem crossing, an alternative process of the triplet state formation, which results in only one triplet exciton from one photoexcited singlet state.

We will report on our effort to expand the basis of SF materials. Using time-resolved transient absorption and fluorescence spectroscopies to probe the photophysical processes, we identified SF in a metallo-supramolecular polymer formed by the coordination of Zn2+ ions to bis(terpyridine-4′-yl)terthiophene ligand [4]. In this case, since S1 is energetically lower than the coupled triplet-pair state, the system requires photoexcitation to a higher excited state (Sn, instead of S1) in order to be able to undergo fission into two triplets (2T1).

Our effort continued with synthesis of two derivatives of 3,6-di(thiophen-2-yl)-2,5-dihydropyrrolo[3,4-c]pyrrole-1,4-dione (TDPP) [5]. By varying the chemical structure and film preparation method, we influenced the resulting rate constant for triplet formation. We observed behavior that is consistent with the SF phenomenon, i.e. an ultrafast formation of triplet states and a strong dependence on solid phase structure [3].

References:

[1] M. A. Baldo, D. F. O'Brien, Y. You, A. Shoustikov, S. Sibley, M. E. Thompson and S. R. Forrest, Nature 395, 151. (1998). [2] A. V. Ruban, R. Berera, C. Ilioaia, I. H. M. van Stokkum, J. T. M. Kennis, A. A. Pascal, H. van Amerongen, B. Robert, P. Horton and R. van Grondelle, Nature 450, 575. (2007). [3] M. Smith, and J. Michl, Chemical Reviews 110, 6891. (2010). [4] D. Rais, J. Pfleger, M. Menšík, A. Zhigunov, P. Štenclová, J. Svoboda and J. Vohlídal, J. Mater.

Chem. C 5, 8041. (2017). [5] C. M. Mauck, P. E. Hartnett, E. A. Margulies, L. Ma, C. E. Miller, G. C. Schatz, T. J. Marks and M. R. Wasielewski, J. Am. Chem. Soc. 138, 11749. (2016).

Acknowledgement: The work was supported by the Czech Science Foundation, grant No. 17-02578S.

1 Ultraflexible photodetectors based on organic field-effect transistors 2 -mandatory blank line-3 Yunlong Guo 4 -mandatory blank line-5 Organic Solid Laboratory, Institute of Chemistry, Chinese Academy of Sciences. 6 Beijing, 100190 P. R. China 7 8 -mandatory blank line-9 The growing demands of artificial intelligence, smart robotics, and human prosthetics urge for visual

10 systems, pressure/mechano, and thermo/temperature sensors identical to biological sensory 11 receptors.1 Among these purposes, artificial visual systems are indispensable for night surveillance 12 and medical imaging applications. For artificial visual system, photodetectors with organic 13 semiconductors are very attractive due to the unique properties of band-gap designing, solution 14 processable, intrinsic flexible and light weight, as well as low cost.1

15 Recently, we integrate prepared ultrathin and high sensitive detectors based on organic electronics. 16 The magnification effect of organic transistors enhances ratio of light/dark current from 104 to 108.2

17 When we functionalized the organic transistors with memory ability. A retina-like photosensor 18 transduces NIR (850 nm) into nonvolatile memory and acts as a dynamic photoswitch under green 19 light (550 nm). In doing this, a filter-free but color-distinguishing photosensor is demonstrated that 20 selectively converts NIR optical signals into nonvolatile memory.3 Very recently, we proposed a 21 ferroelectric/ electrochemical modulated organic synapse, attaining three prototypes of plasticity: 22 STP/LTP by electrochemical doping/de-doping and ferroelectric-LTP from dipole switching. The 23 device supplements conventional electrochemical transistors with 10000-second-persistent non-24 volatile plasticity and unique threshold switching properties. As a proof of- concept for an artificial 25 visual-perception system, an ultraflexible, light-triggered organic neuromorphic device (LOND) is 26 constructed by this synapse. The LOND transduces incident light signals with different frequency, 27 intensity, and wavelength into synaptic signals, both volatile and non-volatile.4

28 29 Figure 1. Synapse based on organic electronics. 30 References 31 [1] Y. Guo, G. Yu, Y. Liu, Adv. Mater. 22, 4427-4447 (2010). 32 [2] H. Wang , H. Liu , Q. Zhao , C. Cheng , W. Hu , Y. Liu, Adv. Mater. 28, 624–630 (2016). 33 [3] H. Wang, H. Liu, Q. Zhao, Z. Ni, Y. Zou, J. Yang, L. Wang, Y. Sun, Y. Guo, W. Hu, Y. Liu Adv. Mater., 34 29, 1701772(2017). 35 [4] H. Wang, Q. Zhao, Z. Ni, Q. Li, H. Liu, Y. Yang, L. Wang, Y. Ran, Y. Guo, W. Hu, Y. Liu, Adv. Mater., 36 30, 1803961 (2018). 37 38 39 40 41 This is the last line of your abstract.

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2D/3D Hybrid Perovskite Interfaces and Physics therein for Stable and Efficient Solar Cells

Valentin I. E. Queloz1, Albertus A. Sutantu,1 Marine Bouduban2, Inès Garcia-Benito1, Mohammad

Nazeeruddin1, Claudio Quarti3, David Beljonne3, Giulia Grancini1,*

1 Group for Molecular Engineering of Functional Materials, Institute of Chemical Sciences and

Engineering, EPFL Valais Wallis, Rue de l’Industrie 17, CP 440, CH-1951 Sion, Switzerland 2Photochemical Dynamics Group, EPFL, 1015 Lausanne, Switzerland

3 Laboratory for Chemistry of Novel Materials, University of Mons, Place du Parc 20, B-7000 Mons,

Belgium

Solar energy can lead a “paradigm shift” in the energy sector with a new low-cost, efficient, and

stable technology. Nowadays, three-dimensional (3D) methylammonium lead iodide perovskite solar

cells are undoubtedly leading the photovoltaic scene with their power conversion efficiency (PCE)

>23%, holding the promise to be the near future solution to harness solar energy [1]. Tuning the

material composition, i.e. by cations and anions substitution, and functionalization of the device

interfaces have been the successful routes for a real breakthrough in the device performances [2].

However, poor device stability and still lack of knowledge on device physics substantially hamper

their take-off. Here, I will show a new concept by using a different class of perovskites, arranging into

a two-dimensional (2D) structure, i.e. resembling

natural quantum wells. 2D perovskites have

demonstrated high stability, far above their 3D

counterparts [3]. However, their narrow band

gap limits their light-harvesting ability,

compromising their photovoltaic action.

Combining 2D and 3D into a new hybrid 2D/3D

heterostructure will be here presented as a new

way to boost device efficiency and stability,

together. The 2D/3D composite self-assembles

into an exceptional gradually organized interface

with tunable structure and physics. To exploit new synergistic function, interface physics, which

ultimately dictate the device performances, is explored, with a special focus on energy and charge

transfer dynamics, as well as charge recombination and trapping processes happening over a time

scale from fs to ms. As shown in Fig.1, when 2D perovskite is used on top of the 3D, charge transfer

happens, while electron hole recombination at the perovskite/hole transporter interface is

prevented. This results in improved device efficiency. In concomitance, the stable 2D perovskite is

used as a sheath to physically protect the 3D underneath, with the aim to enhance the device

stability. The joint effect leads to PCE=20% which is kept stable for 1000 h [3,4]. Incorporating the

hybrid interfaces into working solar cells is here demonstrated as an interesting route to advance in

the solar cell technology bringing a new fundamental understanding of the interface physics at multi-

dimensional perovskite junction. The knowledge derived is essential for a deeper understanding of

the material properties and for guiding a rational device design, even beyond photovoltaics.

References

[1] http://www.nrel.gov/ncpv/images/efficiency_chart.jpg.

[2] J.-P. Correa-Baena et al., Science 358, 739–744 (2017).

[3] I. Garcia-Benito et al. Chem. Mater., 30 (22), 8211–8220 (2018).

[4] K. Taek Cho et al. Nano Lett. 18, 5467–5474 (2018).

Fig. 1. 20% Efficient Solar cell based on 3D/2D

interface and charge dynamics therein.

Hybrid lead halide perovskite as a non-excitonic triplet sensitiser for triplet fusion

upconversion

Frederik Eistrup1, Klaus Schwarzburg2, Sergiu Levcenco3, Klaus Lips1, Eva Unger4,5 , Rowan MacQueen1

1Institute for Nanospectroscopy, Helmholtz-Zentrum Berlin, Germany 2Department Nanoscale Structures and Microscopic Analysis, Helmholtz-Zentrum Berlin, Germany

3Department Structure and Dynamics of Energy Materials, Helmholtz-Zentrum Berlin, Germany 4Young Investigator Group Hybrid Materials Formation and Scaling, Helmholtz-Zentrum Berlin,

Germany 5Chemical Physics and NanoLund, Lund University, Lund, Sweden

Sensitised triplet fusion upconverters are photonic systems based on organic chromophores, which

output significantly anti-Stokes shifted photoluminescence at potentially mild excitation densities.

Triplet fusion occurs upon the encounter of two triplet excitons diffusing within the upconverting

medium, which is usually a dense film or solution of polycyclic aromatic hydrocarbon derivatives [1].

Populating the triplet manifold of the system is the task of the triplet sensitiser. This is invariably a

nanomaterial, such as a metal-organic complex or a metal chalcogenide nanocrystal, in which the

excited state photophysics are exciton-dominated. Exciton mobility is thus a central concern in

sensitised triplet fusion upconversion. The low exciton mobility of many organic materials can be an

impediment to producing efficient systems [2].

In a new approach for photonic upconversion, we found that photoexcited carriers in thin film

methylammonium lead iodide perovskite (MAPI) could generate triplet excitons in a surface coating

of rubrene, a common triplet fusion upconverter. The triplet sensitisation mechanism does not rely

on the existence of an exciton in the sensitiser material, proceeding instead by the sequential

transfer of nongeminate charge carriers. The result is that highly mobile photoexcited charge carriers

in MAPI are harnessed to drive the exciton-reliant process of triplet fusion upconversion in rubrene.

The process enables an energy-funneling effect, sidestepping the exciton mobility problems endemic

to nanomaterial triplet sensitisers. Optimised versions of the MAPI-organic dye upconverters

reported here should therefore permit efficient upconversion conditions to be obtained at very low

irradiance. The efficient interconversion of excitons and charges at the MAPI-organic dye interface is

also of potential interest for other optoelectronic applications, such as lasing [3].

[1] T.F. Schulze, T.W. Schmidt, Energy Environ. Sci., 8, 103-125. (2015).

[2] K. Sripathy, R.W. MacQueen, Y.Y. Cheng, M. Dvorak, D.R. McCamey, N.D. Treat, N. Stingelin, T.W.

Schmidt, Journal Mat. Chem. C, 3, 616-622. (2014).

[3] F. Mathies, P. Brenner, G. Hernandez-Sosa, I.A. Howard, U.W. Paetzold, U. Lemmer, Optics

Express, 26, A144-A152. (2018).

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Neuromorphic synchronization of organic electrochemical devices

Dimitrios A. Koutsouras,1 Themis Prodromakis,2 George G. Malliaras,3 Paul W. M. Blom,4

Paschalis Gkoupidenis1

1Max Planck Institute for Polymer Research, Ackermannweg 10, 55128 Mainz (Germany)

2Electronic Materials & Devices Research Group, Zepler Institute, University of Southampton,

University Road, SO17 1BJ Southampton (United Kingdom) 3Electrical Engineering Division, Department of Engineering, University of Cambridge, 9 JJ Thomson

Ave, Cambridge CB3 0FA (United Kingdom)

Nowadays, there is an imperative need for novel computational concepts for managing the enormous data volume produced by the contemporary Information Technologies. The inherent capability of the brain to cope with this kind of signals constitutes the most efficient computational paradigm for biomimicry. Emulating the information processing functions of the brain at the device or circuit level, constitutes the main scope of neuromorphic computing. [1] Organic materials for neuromorphic computing have been recently emerged. [2-8] The main pathway in neuromorphic devices is the emulation of various synaptic plasticity mechanisms at the single device level. In biological neural networks, these mechanisms express a form of structural connectivity. In addition to structural connectivity, higher - order phenomena also exist in biological networks that promote a functional type of connectivity between neural populations. [9] For example, global voltage oscillations induce synchronization of neural populations giving thus rise to a form of functional connectivity between them, since synchronized populations share common temporal information. [10] In this work we show how an array of organic electrochemical devices that share a common electrolyte, can be synchronized with a global voltage oscillation. Synchronization is induced in a specific phase window of the global oscillation, which is reminiscent of oscillations in biological networks. These results provide a pathway toward the emulation of more biologically plausible phenomena in neuromorphic device architectures, such as functional connectivity through global oscillations.

[1] C. Mead, Proc. IEEE 78, 1629-1636 (1990). [2] P. Gkoupidenis, N. Schaefer, B. Garlan and G. G. Malliaras, Adv. Mater. 27, 7176-7180 (2015). [3] P. Gkoupidenis, N. Schaefer, X. Strakosas, J. A. Fairfield and G. G. Malliaras, Appl. Phys. Lett. 107, 263302 (2015). [4] P. Gkoupidenis, D. A. Koutsouras, T. Lonjaret, J. A. Fairfield, and G. G Malliaras, Sci. Rep. 6, 27007 (2016). [5] P. Gkoupidenis, S. Rezaei-Mazinani, C. M. Proctor, E. Ismailova and G.G. Malliaras, AIP Adv. 6, 111307 (2016). [6] P. Gkoupidenis, D. A. Koutsouras and G. G. Malliaras, Nat. Commun. 8, 15448 (2017). [7] D. A. Koutsouras, G. G. Malliaras, P. Gkoupidenis, MRS Commun. 8, 493-497 (2018). [8] Y. van de Burgt, E. Lubberman, E. J. Fuller, S. T. Keene, G. C. Faria, S. Agarwal, M. J. Marinella, A. A. Talin and A. Salleo, Nat. Mater. 16, 414 (2017). [9] F. Varela, J.P. Lachaux, E. Rodriguez and J. Martinerie, Nat. Rev. Neurosci. 2, 229 (2001). [10] G. Buzsáki, and A. Draguhn, Science 304, 1926-1929 (2004).

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1 Towards 2D Layered Hybrid Perovskites With Enhanced Functionality. 2 3 L. Lutsen1, D. Vanderzande2, 1, W. Van Gompel2, R. Herckens2, P. - H. Denis2, M. Mertens2, T. 4 Aernouts3, J. D'Haen4, B. Ruttens4, K. Van Hecke5

6 1 IMEC, Imomec, Diepenbeek (Belgium) 7 2 Hasselt University, WET/OBPC/HyMat, Diepenbeek (Belgium) 8 3 IMEC, Leuven (Belgium) 9 4 Hasselt University, IMO, Diepenbeek (Belgium)

5 Gent University, Department of Chemistry, Gent (Belgium) 11 12 Recently organic-inorganic perovskite hybrid materials have been developed for solar cell

13 applications reaching record efficiencies of more than 23%. Furthermore, these materials allow

14 to move from a fundamentally 3D structure using small organic molecules to essentially 2D layered

structures using larger organic molecules. This opens an avenue towards a quite new class of organic-

16 inorganic nanocomposites in which the inorganic perovskite sheet acts as a template for the self-

17 assembly of organic chromophores confined between the sheets of the inorganic layer. Thus the

18 complexity of the organic interlayer in organic-inorganic hybrid perovskites can be increased by

19 introducing additional secondary interactions between different organic components, e.g. pi-

interactions. A fluent transition of electro-optical properties can be achieved of the inorganic part

21 from confined 2D structures to strongly delocalized quasi-3D structures. The use of carbazole

22 ammonium salts in 2D hybrid perovskites leads to materials for solar cells with enhanced

23 photoconductivity and stronger resistance toward moisture yielding solar cells with enhanced

24 stability [1]. Also, the use of pyrene ammonium salts to synthesize 2D hybrid perovskites has been

explored and initial results on the structure and optoelectronic properties will be discussed [2]. In

26 combination with the introduction of extra secondary interactions in the organic layer, a material is

27 obtained with an exceptionally low bandgap.

28 29 [1] Multi-layered hybrid perovskites templated with carbazole derivatives: optical properties,

enhanced moisture stability and solar cell characteristics. Roald Herckens, Wouter T. M. Van Gompel, 31 Wenya Song,bc Maria C. Gelvez-Rueda, Arthur Maufort, Bart Ruttens, Jan D'Haen, Ferdinand C. 32 Grozema, Tom Aernouts, Laurence Lutsen and Dirk Vanderzande. J. Mater. Chem. A, 2018, 6, 22899. 33 DOI: 10.1039/c8ta08019d. 34 [2] Low-dimensional Hybrid Perovskites Containing an Organic Cation with an Extended Conjugated

System: Tuning the Excitonic Absorption Features Wouter T.M. Van Gompel, Roald Herckens, Kristof 36 Van Hecke, Bart Ruttens, Jan D’Haen, Laurence Lutsen and Dirk Vanderzande. ChemNanoMat 2019, 37 5. Accepted. DOI: 10.1002/cnma.201800561.

b)

Electron Transfer para

No Electron Transfer

c)

Spatial control of electrical currents in nano-porous graphene by chemical engineering

Isaac Alcón,1 Gaetano Calogero,1 Nick R. Papior,1 Mads Brandbyge1

1Centre for Nanostructured Graphene, Department of Physics, Technical University of Denmark (DTU),

Lyngby (Denmark)

The electronic properties of pi-conjugated systems may be controlled via structural means such as torsion angles [1] or meta/para connectivities through benzene rings [2]. For instance, it has been experimentally shown that an added negative charge in para-connected pi-conjugated bi-radicals may extend from one extreme of the molecule to the other (grey areas in Fig. 1a) whereas it remains localized in one of the extremes if the pi-conjugated connection is meta (Fig. 1b) [3]. Very recently, the first atomically precise nano-porous graphene (NPG) has been experimentally prepared through a bottom-up approach, featuring graphene nano-ribbons (GNRs) connected in para

to each other, as shown in Fig. 1c [4]. Via multi-scale density-functional theory (DFT) and tight-binding (TB) calculations, it has been demonstrated that electrons injected locally in the synthesized NPG spread over the structure, as shown in Fig. 1d with the associated bond currents [5]. In this work we demonstrate that such an electronic delocalization effect is caused by the para-connection between GNRs and propose a new type of NPG with GNRs connected in meta. Based on multi-scale simulations we demonstrate that such meta-connection leads to full localization of electronic currents in single GNR channels, as shown in Fig 1e, which opens the door for the design of full carbon nano-circuitry. Experimental realization of GNRs bonded with meta-connections have recently been reported [6], which highlights the experimental feasibility of our proposed structures.

Fig. 1. (a) Para-connected and (b) meta-connected mixed-valence compounds where the negative

charge may, and may not, delocalize between both extremes of the molecule, respectively. (c) STM

image of the bottom-up prepared nano-porous graphene (NPG) composed of laterally bonded

graphene nano-ribbons (see inset), from [4]. Injected electron currents (small red dot) within (d) para-

NPG (injection in middle region) and (e) meta-NPG (injection in bottom region) modelled using tight-

binding transport simulations.

[1] L. Venkataraman, J. E. Klare, C. Nuckolls, M. S. Hybertsen and M. L. Steigerwald, Nature, 442, 904– 907 (2006) [2] C. R. Arroyo, S. Tarkuc, R. Frisenda, J. S. Seldenthuis, C. H. M. Woerde, R. Eelkema, F. C. Grozema and H. S. J. van der Zant, Angew. Chemie Int. Ed., 52, 3152–3155, (2013) [3] C. Rovira, D. Ruiz-Molina, O. Elsner, J. Vidal-Gancedo, J. Bonvoisin, J.-P. Launay and J. Veciana, Chem. - A Eur. J., 7, 240–250 (2001) [4] C. Moreno, M. Vilas-Varela, B. Kretz, A. Garcia-Lekue, M. V. Costache, M. Paradinas, M. Panighel, G. Ceballos, S. O. Valenzuela, D. Peña and A. Mugarza, Science, 360, 199–203 (2018) [5] G. Calogero, N. R. Papior, B. Kretz, A. Garcia-Lekue, T. Frederiksen and M. Brandbyge, Nano Lett., DOI:10.1021/acs.nanolett.8b04616 (2018) [6] M. Shekhirev, P. Zahl and A. Sinitskii, ACS Nano, 12, 8662–8669 (2018)

Functional π-Electron Systems14th International Symposium on

Abstracts Poster Presentation

Plenary Lectures

Wednesday, June 5th

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Interfacing with the brain using organic electronics

George Malliaras

Department of Engineering, University of Cambridge, Cambridge (UK)

One of the most important scientific and technological frontiers of our time is the interfacing of electronics with the human brain. This endeavour promises to help understand how the brain works and deliver new tools for diagnosis and treatment of pathologies including epilepsy and Parkinson’s disease. Current solutions, however, are limited by the materials that are brought in contact with the tissue and transduce signals across the biotic/abiotic interface. Recent advances in organic electronics have made available materials with a unique combination of attractive properties, including mechanical flexibility, mixed ionic/electronic conduction, enhanced biocompatibility, and capability for drug delivery. I will present examples of novel devices for recording and stimulation of neurons and show that organic electronic materials offer tremendous opportunities to study the brain and treat its pathologies.

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Understanding how hierarchical structure impacts charge transport in molecular and

polymeric semiconductors

Kaichen Gu,1 Geoffrey Purdum,1 Yueh-Lin Loo1,2

1Department of Chemical and Biological Engineering, Princeton University, Princeton (USA) 2Andlinger Center for Energy and the Environment, Princeton University, Princeton (USA)

Thin films comprising molecular semiconductors and conjugated polymers are structurally complex;

these structural heterogeneities can pose significant impediments to macroscopic charge transport.

This talk will focus on two ways in which structural development impacts charge transport in such

polycrystalline thin films, with the first and second examples highlighting the roles tie chains and

polymorphism, respectively, play in supporting charge transport.

While tie chains that connect crystallite domains are generally acknowledged as critical for

macroscopic charge transport in conjugated polymers, direct visualization, let alone quantification, of

their role has been challenging. Extending the Huang-Brown model, a framework commonly used to

elucidate the structural origins of mechanical properties of polyolefins, to examining charge

transport in model P3HT thin films, we found a threshold tie-chain fraction of 10-3 , below which

intercrystallite connectivity limits macroscopic charge transport. Structural characterization of these

films suggests intracrystallite disorder to be the bottleneck that in turn limits charge transport when

the tie-chain fraction is above percolation and the crystallites are interconnected. This study affirms

the importance of connectivity between crystalline domains, with the Huang-Brown model

implicating long polymer chains with rigid backbone to be more conductive to macroscopic charge

transport [1].

The weak intermolecular forces inherent to organic semiconductors give rise to polymorphism, or

the ability for these materials to adopt multiple solid-state packing arrangements. And since the

details of intermolecular packing can substantively influence charge transport, the ability to predict

which of the polymorphs available is preferentially accessible and stable should shed light on charge

transport characteristics. In the second half of my talk, I will discuss a simple framework that directly

correlates the presence of short intermolecular contacts with polymorphic stability.

Quantification starts with assessing whether intermolecular contacts within a crystal structure are

smaller than the sum of the van der Waals radii of the same atoms. Polymorphs with such short

intermolecular contacts are substantially more resistant to polymorphic transformation while those

without exhibit an added degree of freedom for molecular rearrangement; the said polymorph can

thus be easily destabilized with post-deposition processing. Starting with a series of core-chlorinated

naphthalene diimide derivatives, we show this framework to be widely applicable to a wide range of

molecular semiconductors, and even extending to pharmaceutics and biological building blocks. In

this era of machine learning and materials by design, this framework can help refine computational

predictions by identifying the polymorphs that are practically stable [2].

[1] Kaichen Gu, Chad R. Snyder, Jonathan Onorato, Christine K. Luscombe, August W. Bosse, Yueh-Lin

Loo, ACS Macro Letters 7, 1333. (2018).

[2] Geoffrey E. Purdum, Nicholas G. Telesz, Karol Jarolimek, Sean M. Ryno, Thomas Gessner, Nicholas

D. Cavy, Antohny J. Petty, II, Yonggang Zhen, Ying Shu, Antonio Facchetti, Gavin E. Collis, Wenping

Hu, Chao Wu, John E. Anthony, R. Thomas Weitz, Chad Risko, Yueh-Lin Loo, J. Am. Chem. Soc. 140,

7519. (2018).

Functional π-Electron Systems14th International Symposium on

Abstracts Poster Presentation

Invited Lectures

Wednesday, June 5th

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49

Distance from 8ceq

f ~

1: ~

i EG,mln - --

Shearing Speed

Solution-shearing: getting more out of an already quite standard coating method for organic field effect transistors

-mandatory blank line-Katherina Haase1,2, Cecilia Teixeira da Rocha1,2, Mike Hambsch1,2, Stefan C.B. Mannsfeld1,2

-mandatory blank line-1Center for Advancing Electronics Dresden (cfaed), Technische Universität Dresden, Dresden, Germany

2Department of Electrical and Computer Engineering, Technische Universität Dresden, Dresden,

Germany

-mandatory blank line-Solution-shearing and many other meniscus-guided coating methods have become fairly popular, in particular in the OFET community, ever since its use yielded record-performance devices for soluble semiconductor materials such as TIPS-pentacene or 2,7-dioctyl[1]benzothieno[3,2-b] benzothiophene (C8-BTBT) in which the carrier mobilities significantly surpassed those obtained with vacuum-deposited or spin-coated films. In this presentation we cover some of our recent results that focus on further refining and improving various aspects of the solution-shearing method for OFET devices, not only for the active layer but also for the dielectric material and even electrodes.

In the first part, we discuss how the engineering of the solution-shearing ink through blending of the small organic semiconductor materials with polymers additives improves the thin film morphology, reproducibility and OFET device performance. At the optimized conditions, gate voltage-independent charge carrier mobilities as high as 12 cm²/Vs are achieved for the organic semiconductor C8-BTBT. For TIPS-pentacene, such blended inks also produce very high mobility values of even over 10 cm²/Vs, rivalling the previous records we had in the past obtained from coating single crystalline films with the much more complex FLUENCE method.[1] While solution-shearing has so far been mainly employed for the deposition of soluble organic semiconducting materials, it is an excellent method to produce ultra-thin, homogenous films over large areas in general. Despite that, its application to the coating of gate dielectric layers has been very limited to date. In the second part of this talk, we describe how solution-shearing can be used for the coating of dielectric films that are not only ultra-smooth and exhibit exceptionally high capacitance, but can also serve as substrates for subsequent active layer solution coating steps. Using this approach, we fabricated OFETs that operate at very low voltages (< 1V) that still have very high carrier mobilities of up to 6.9 cm²/Vs, improved subthreshold characteristics and on-off ratios, but also exhibit environmental and operational stability. In the final portion of this talk, we discuss very recent results that involve a modification to the solution-coating method: the introduction of high frequency vibrations. We show by that incorporating such vibrations in the coating head assembly we are able to mitigate contact line instabilities that frequently occur during the deposition of polymer semiconductor films due to stick-and-slip instabilities. Using optimized frequencies and vibration amplitudes, the resulting OFET carrier mobilities are improved and more importantly, the window of coating speeds that produce closed films of common donor-acceptor polymers for OFETs is more than doubled.

[1] Y. Diao, B. C.K. Tee, G. Giri, J. Xu, D. H. Kim, H. A. Becerril, R. M. Stoltenberg, T. H. Lee, G. Xue, S.C.B. Mannsfeld, Z. Bao, et. Al, Nature Materials 12, 665–671 (2013)

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13 14 HN)_NH B C N 0 F

Al Si p s Cl \

a Ge As Se Br

In Sn Sb Te

Main-group-containing p-electron materials with structural constraint

Shigehiro Yamaguchi

Institute of Transformative Bio-Molecules (ITbM), Nagoya University,

Furo, Chikusa, Nagoya 464-8602, Japan

Incorporation of main group elements into p-conjugated skeletons is a powerful strategy to develop

new optoelectronic organic materials with unusual properties. Representative design principles are

to make use of an orbital interaction between a p skeleton and a main-group element moiety.

Conformational constraint often plays a crucial role to gain an optimal orbital interaction. In addition,

this is also important to gain high chemical and/or photo-stability.[1] Based on this strategy, we have

so far synthesized various types of functional p-electron materials. In this presentation, we would like

to report recent progress in the development of some new main-group element-containing p-

electron materials. In particular, we have recently succeeded in the synthesis of a boron-stabilized

triphenylmethyl radical, which shows bright fluorescence as well as ambipolar charge carrier

transport properties.[2] We have also developed new P=O-containing ladder-type dyes, which can

show exceptionally high photostability, and thereby can be employed as promising molecules for

super-resolution STED imaging.[3]

References

[1] M. Hirai, N. Tanaka, M. Sakai, S. Yamaguchi, Chem. Rev., in press (2019).

[2] (a) T. Kushida, S. Shirai, N. Ando, T. Okamoto, H. Ishii, H. Matsui, M. Yamagishi, T. Uemura, J.

Tsurumi, S. Watanabe, J. Takeya, S. Yamaguchi, J. Am. Chem. Soc., 139, 14336 (2017). (b) N. Ando,

T. Kushida, S. Yamaguchi, Chem. Commun., 54, 5213 (2018).

[3] (a) C. Wang, A. Fukazawa, M. Taki, Y. Sato, T. Higashiyama, S. Yamaguchi, Angew. Chem. Int. Ed.,

54, 15213 (2015). (b) C. Wang, M. Taki, Y. Sato, A. Fukazawa, T. Higashiyama, S. Yamaguchi, J. Am.

Chem. Soc., 139, 10374 (2017). (c) M. Grzybowski, M. Taki, K. Senda, Y. Sato, T. Ariyoshi, Y. Okada,

R. Kawakami, T. Imamura, S. Yamaguchi, Angew. Chem. Int. Ed., 57, 10137 (2018).

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WHAT IS THE BINDING ENERGY OF A CHARGE TRANSFER STATE IN AN ORGANIC SOLAR

CELL?

-mandatory blank line-

Stavros Athanasopoulos1, Franz Schauer,2 Vojtech Nádaždy3, Mareike Weiß,4 Frank-Julian Kahle,4

Heinz Bässler5, Anna Köhler,4,5

-mandatory blank line-1 Departamento de Física, Universidad Carlos III de Madrid, Madrid, SPAIN,

2 Faculty of Applied Informatics, Tomas Bata University in Zlín, CZECH REPUBLIC, 3 Institute of Physics of the Slovak Academy of Sciences, Bratislava, SLOVAKIA,

4 Soft Matter Optoelectronics, University of Bayreuth, Bayreuth, GERMANY, 5 Bayreuth Institute of Macromolecular Research (BIMF), University of Bayreuth, Bayreuth, GERMANY

mandatory blank line-

The high efficiencies reported for organic solar cells, and reports on an almost negligible thermal

activation for the photogeneration of charge carriers have called into question whether

photoinduced interfacial charge transfer states are bound by a significant coulomb attraction, and

how this can be reconciled with very low activation energies. We have addressed this question here

in a combined experimental and theoretical approach. We determined the interfacial binding energy

of a charge-transfer state in a blend of MeLPPP:PCBM, using energy resolved electrochemical

impedance spectroscopy and find it to be about 0.5 eV. Temperature-dependent photocurrent

measurements on the same films, however, give an activation energy that is about one order of

magnitude lower. Using analytical calculations and MC simulation we illustrate how (i) interfacial

energetics and (ii) topology of transport reduce the activation energy required to separate the

interfacial electron-hole pair, with about equal contributions.

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The impact of the molecular structure of in-plane self-assembled -systems

on their 2D-molecular order and their transport properties

Marcus Halik

Organic Materials & Devices – OMD,

Department of Materials Science University Erlangen-Nürnberg, Erlangen (Germany)

The charge transport in thin films of -conjugated systems – in particular the long-distance lateral transport in transistor devices – critically depends on the orientation of the -system “edge-on” to the surface and on the efficient -interaction. The edge-on orientation can be realized by introducing surface selective anchor moieties to the chromophore, enabling the formation of self-assembled monolayers (SAMs). Due to the huge variability of suitable chromophores as transport materials, which differ simply in their fashion (balls, plates, sticks, squares etc.) and in substitution pattern (e.g. space demanding chains to provide solubility), the in-plane -stacking occurs a crucial parameter. The talk will present an overview of various -systems and the performance of such functional molecules in so called self-assembled monolayer field-effect transistors (SAMFETs). Ideas towards perfectly ordered 2D lattices composed of oriented -systems will be discussed.

Functional π-Electron Systems14th International Symposium on

Abstracts Poster Presentation

Contributed Lectures

Wednesday, June 5th

1 From Simple Anthracene to Structurally Defined Perylene- and Coronene Nanoribbons

2

3 Michael Mastalerz, Xuan Yang, Frank Rominger

4

5 Organisch-Chemisches Institut, Ruprecht-Karls-Universität Heidelberg, Heidelberg (Germany)

6

7 In recent years, the synthesis of larger molecular and structurally defined cut-out structures of

8 graphene became more and more into the focus of interest, because by control of size and

9 geometry, physical properties such as band gaps can be adjusted.[1,2] Based on recent

10 developments in our group to synthesize diarenoperylenes and bis(heteroareno)coronenes in good

11 yields,[3,4] now a small series of perylene- and coronene-based nanoribbons was accessible applying

12 similar chemistry. [5] In the talk, the synthetic strategies and their realizations to small series of

13 perylene- and coronene nanoribbons is presented, as well as the photophysical and electrochemical

14 investigation of the compounds discussed. Shown below is the X-ray structure (Fig. 1) of the second

15 member of the perylene-based series with nine annulated rings (O-9) and the UV/vis spectra as well

16 as photographs of emissions of all members of the same series (Fig. 2).

17 18 Fig. 1. Single-crystal X-ray structure of a bisperylene nanoribbon with nine rectilinearly annulated

19 rings (O-9).

250 300 350 400 450 500 550 600 6500

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(×

104 M

-1 c

m-1)

Wavelength (nm)

O-5 O-9 O-13

ex@366 nm (5.0 10-6 M)

O-5 O-9 O-13

20 21 Fig. 2. Left: UV/vis absorption of perylene-based nanoribbons. Right: photographs of emissions

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23 [1] Long Chen, Yenny Hernandez, Xinliang Feng, Klaus Müllen, Angew. Chem. Int. Ed. 51, 7640-

24 7654. (2012)

25 [2] Akimitsu Naria, Xiao.Ye Wang, Xinliang Feng, Klaus Müllen, Chem. Soc. Rev. 44, 6616-6643. (

26 2015)

27 [3] Gang Zhang, Frank Rominger, Ute Zschieschang, Hagen Klauk, Michael Mastalerz, Chem. Eur.

28 J. 22, 14840-14845. (2016)

29 [4] Xuan Yang, Frank Rominger, Michael Mastalerz, Org. Lett. 20, 7270-7273. (2018)

30 [5] Xuan Yang, Frank Rominger, Michael Mastalerz, unpublished results.

On Mechanism of hole transfer in Non-fullerene (NF) Organic Solar Cells

Yanfeng Liu 1, Jianyun Zhang 2, Yingzhi Jin 1, Nannan Yao 1, Xiaozhang Zhu 2 and Fengling Zhang 1

1 Department of Physics, Chemistry and Biology, Linköping University, Linköping (Sweden) 2 Beijing National Laboratory for Molecular Sciences, CAS Key Laboratory of Organic Solids, Institute of

Chemistry, Chinese Academy of Sciences, Beijing (P. R. China)

To efficiently harvest photoinduced current in organic solar cells by extending the coverage of the solar spectrum, many non-fullerene (NF) electron acceptors with complementary absorption spectra are synthesized, which indeed enables the power conversion efficiency of organic solar cells up to 14% in single junction and 17% in tandem devices.[1, 2]

There have been intensive studies on electron transfer from electron donors to various fullerene acceptors in fullerene based organic solar cells.[3, 4] However, the mechanism of efficient hole transfer from non-fullerene acceptors (or hole donor, denoted as Dh) to molecular or polymeric electron donors (or hole acceptors, denoted as Ah) is still not fully understood although considerable contribution from non-fullerene Dh materials to photoinduced current in non-fullerene solar cells. There are several reports on high performance non-fullerene organic solar cells with very small or even close to zero LUMO or/and HOMO offsets between two photoactive components, which challenges the theories on charge generation derived in fullerene based organic solar cells.[5, 6] Currently, to increase the efficiency of organic solar cells, more attention is paid on generating charge with minimized photo-voltage loss by matching energy levels of donors and acceptors.[7, 8] To understand the mechanism of non-fullerene organic solar cells, charge transport and extraction at electrodes also need to be considered.

Here we will present our study on the mechanism of efficient hole transfer from Dh to Ah in non-fullerene organic solar cells. Based on the results, efficient hole transfer from Dh to Ah is not only depends on the offset of HOMOs of Dh and Ah, but also charge transport and extraction at electrodes. Therefore, a comprehensive strategy including both charge generation and extraction is desired to further enhancing the PCE of the organic solar cells.

[1] S. Zhang, Y. Qin, J. Zhu and J. Hou, Adv. Mater., DOI: 10.1002/adma.201800868 (2018) [2] L. Meng, Y. Zhang, X. Wan, C. Li, X. Zhang, Y. Wang, X. Ke, Z. Xiao, L. Ding and R. Xia, Science,

361, 1094-1098. (2018) [3] K. Vandewal, A. Gadisa, W. D. Oosterbaan, S. Bertho, F. Banishoeib, I. Van Severen, L. Lutsen,

T. J. Cleij, D. Vanderzande and J. V. Manca, Adv. Funct. Mater., 18, 2064-2070. (2008) [4] D. Veldman, S. C. J. Meskers and R. A. J. Janssen, Adv. Funct. Mater., 19, 1939-1948. (2009) [5] S. Chen, Y. Wang, L. Zhang, J. Zhao, Y. Chen, D. Zhu, H. Yao, G. Zhang, W. Ma, R. H. Friend, P.

C. Y. Chow, F. Gao and H. Yan, Adv. Mater., 30, e1804215. (2018) [6] J. Liu, S. Chen, D. Qian, B. Gautam, G. Yang, J. Zhao, J. Bergqvist, F. Zhang, W. Ma, H. Ade, O.

Inganäs, K. Gundogdu, F. Gao and H. Yan, Nature Energy, 1, 16089. (2016) [7] N. D. Eastham, J. L. Logsdon, E. F. Manley, T. J. Aldrich, M. J. Leonardi, G. Wang, N. E. Powers-

Riggs, R. M. Young, L. X. Chen, M. R. Wasielewski, F. S. Melkonyan, R. P. H. Chang and T. J. Marks, Adv. Mater., 30, 10.1002/adma.201704263. (2018)

[8] Z. Zheng, O. M. Awartani, B. Gautam, D. Liu, Y. Qin, W. Li, A. Bataller, K. Gundogdu, H. Ade and J. Hou, Adv. Mater., 29, 1604241. (2017)

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Preparation of fused heterocyclic conjugated polymers by multicomponent one-pot

polymerization

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Ru Dong, Qi Zhang, Xuediao Cai

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Key Laboratory of Macromolecular Science of Shaanxi Province, School of Chemistry and Chemical Engineering, Shaanxi Normal University, Xi’an (China)

Due to the significant performance of biological, pharmacological activities and the photoelectric

properties, developing the synthetic method of fused heterocyclic conjugated polymers will be more

interesting[1-4]

. Based on multicomponent one-pot reaction, a new polymerization method for fused

heterocyclic conjugated polymers has been established by the polymerization of aldehydes, azines

and easy-storage and operation acetylene acids through A3-coupling multicomponent reaction under

catalyzed by lewis acids. Such polymerization may exist two polymerization mechanisms, which are

5-exo-dig cyclization and 6-endo-dig cyclization. By designing different substrate and reaction system,

the mechanism of polymerization and cyclic formation mechanism were investigated. We found that

under the optimal condition, when the heteroatom at 1-position of azines is sulfur, this

multicomponent reactions (MCRs) would experience a 5-exo-dig cyclization to form the imidazole

[2.1-b]thiazole skeleton, however, when the heteroatom at 1-position is nitrogen, the MCRs would

experience 6-endo-dig cyclization to form the imidazole [1,2-a] pyrimidine skeleton. Based on this

new reaction, a series of fused heterocyclic conjugated polymers with different heteroatom and

different substitution were synthesized and characterized.

[1] A.-N. A EI-Shorbagi, M. A. Husein, Der Pharma Chemica, 7(5),, 319-328 (2015)

[2] L.-S. Cui, J. U. Kim, H. Nomura, H. Nakanotani, C. Adachi, Angew. Chem. Int. Ed. 55, 6864-6868

(2016)

[3] D. C. Leith, L. V. Kayser, Z. –Y. Han, A. R. Siamaki, E. N. Keyzer, A. Gefen, B. C. Arndtson,

Nature Commu. 6, 7411 (2015)

[4] B. Wei, W. Li, Z. Zhao, A. Qin, R. Hu, B. Z. Tang, JACS, 139, 5075-5084 (2017)

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1 Synthesis of Giant Monodisperse N-Doped Nanographenes

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3 Aurelio Mateo-Alonso1,2

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5 1POLYMAT, University of the Basque Country UPV/EHU. Avenida de Tolosa 72, E-20018 Donostia-San

6 Sebastián, SPAIN

7 2Ikerbasque, Basque Foundation for Science. Bilbao, SPAIN

8 e-mail: amateo@polymat.eu

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10 The discovery of fullerenes, nanotubes, and graphene has stimulated the exploration of synthetic

11 low-dimensional carbon nanostructures. Nanographenes are large monodisperse polycyclic aromatic

12 hydrocarbons that extend in size beyond the nanometer, which show unique electronic, optical and

13 mechanical properties with a lot of potental for electronics, photonics, and energy conversion,

14 among others.[1] The properties of nanographenes are highly dependent on several structural

15 variables such as the number of fused rings and their arrangement, and also the presence of

16 heteroatoms in the structure. The synthesis of extended nanographenes is still a challenging task that

17 requires dealing with insoluble intermediates and products, which overall makes synthesis,

18 purification, characterisation and processing difficult, slowing down the exploration of their

19 fundamental properties and the development of potential applications.

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21 We have recently developed an iterative approach that assembles a small molecular building block

22 into nanographenes of different sizes. In this lecture, such new approach will be showcased by

23 describing the synthesis of several giant monodisperse N-doped nanographenes that extend beyond

24 5 nm in size.[2,3]

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Si Si Si Si Si Si

O ON N N N N N N N N N N NO O O ON N N N N N N N N N N NO O

Si Si Si Si Si Si

26 27

28 [1] a) L. Chen, Y. Hernandez, X. Feng, K. Müllen, Angew. Chem. Int. Ed., 51, 7640-7654 (2012); b) A.

29 Mateo-Alonso, Chem. Soc. Rev., 43, 6311-6324 (2014); c) A. Narita, X.-Y. Wang, X. Feng, K. Mullen,

30 Chem. Soc. Rev. 44, 6616-6643 (2015); d) Y. Segawa, H. Ito, K. Itami, Nat. Rev. Mater. 1, 15002 (2016).

31 [2] D. Cortizo-Lacalle, J. P. Mora-Fuentes, K. Strutyński, A. Saeki, M. Melle-Franco, and A. Mateo-

32 Alonso Angew. Chem. Int. Ed., 57, 703–708 (2018).

33 [3] J. P. Mora-Fuentes, A. Riaño, D. Cortizo-Lacalle, A. Saeki, M. Melle-Franco, A. Mateo-Alonso

34 Angew. Chem. Int. Ed., DOI: 10.1002/anie.201811015 (2019).

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Decoding Charge Recombination Through Charge Generation

Dieter Neher, Safa Shoaee

Optoelectronics of Organic Semiconductors, Institute for Physics and Astronomy, University of

Potsdam, 14476 Potsdam-Golm

In-depth understanding of charge carrier photogeneration and recombination mechanism in organic

solar cells is still an ongoing effort in the community. In donor:acceptor (bulk) heterojunction organic

solar cells charge photogeneration and recombination are inter-related via the kinetics of charge

transfer states – being singlet or triplet states. While high charge photogeneration quantum yields

have been achieved in many donor:acceptor systems, only very few systems have so far shown

significantly reduced bimolecular recombination relative to the rate of encounter of free carriers in

low mobility systems. Herein, we present a meta-analysis of the device performance for numerous

bulk heterojunction organic solar cells for which field dependent photogeneration, charge carrier

mobility and fill factor are determined. From this analysis we find a spin-related factor which is

dependent on the ratio of back electron transfer of the triplet CT states to the decay rate of the

singlet CT states. We show that this factor links the recombination reduction factor to the charge

generation efficiency. It’s only in systems with very efficient charge generation due to the very fast dissociation rate of the CT states that the recombination is strongly suppressed regardless of the

spin-related factor.

F=g=F 0 0 0 0

1/ ~ s H13Cs CsH13

Cs PDF DTS-Ts-PDF 0-A type donor

N,.S,N N,.S,N

65 ~ N-R

/; I/ ~ /;

I \ I \ F R-N I \ CH3 N, ,.N N, ,.N N, ,.N R=--< s s s

NTz FNTz FNTz-T eh·FA CsH13 Nonfullerene acce tor

Development of Organic Semiconductors Containing Fluorine-Substituted Electron-

Accepting Units for Organic Photovoltaics

Yutaka Ie,1,2 Koki Morikawa,1 Shreyam Chatterjee,1 Taichi Moriyama,3 Wojciech Zajazkowski,2

Wojciech Pisula,2 Naresh B. Kotadiya,2 Gert-Jan A. H. Wetzelaer,2 Paul W. M. Blom,2 Yoshio Aso1

1The Institute of Scientific and Industrial Research, Osaka University, Osaka (Japan) 2Max Planck Institute for Polymer Research, Mainz (Germany)

3Ishihara Sangyo Kaisha, Ltd., Shiga (Japan)

Considerable efforts have been devoted to the development of organic semiconductors for organic photovoltaics (OPVs). In terms of material design, the fine-tuning of highest occupied molecular orbital and lowest unoccupied molecular orbital energies is important to acquire both donor and acceptor materials. The straightforward approach to tune these frontier-orbital energy levels is the incorporation of electron-accepting units into -conjugated systems. We previously reported that -conjugated systems having naphtho[2,3-c]thiophene-4,9-dione (C6) or naphtho[1,2-c:5,6-c']bis[1,2,5]thiadiazole (NTz) as electron-accepting units showed good photovoltaic characteristics [1,2]. To further increase the electron-accepting character of these units, we introduced strongly electron-withdrawing fluorine atoms and developed PDF [3,4] and FNTz [5]. The OPV device based on DTS-HT-PDF and PC71BM achieved a high power conversion efficiency (PCE) of 9.12%. This is the first example of PCE exceeding 9% for OPVs with amorphous active layers. The OPV device based on FNTz-Teh-FA and P3HT exhibited a significant improvement of PCE compared to the corresponding nonfluorinated NTz-based cells and reached a high PCE of 3.12%. In this contribution, we discuss the chemical structures-film properties-OPV characteristics relationship.

Figure. Chemical structures.

[1] J. Huang, Y. Ie, M. Karakawa, M. Saito, I. Osaka, Y. Aso, Chem. Mater. 26, 6971 (2014). [2] S. Chatterjee, Y. Ie, M. Karakawa, Y. Aso, Adv. Funct. Mater. 26, 1161 (2016). [3] Y. Ie, K. Morikawa, M. Karakawa, N. B. Kotadiya, G.-J. A. H. Wetzelaer, P. W. M. Blom, Y. Aso, J. Mater. Chem. A 5, 19773 (2017). [4] Y. Ie, K. Morikawa, W. Zajazkowski, W. Pisula, N. B. Kotadiya, G.-J. A. H. Wetzelaer, P. W. M. Blom, Y. Aso, Adv. Energy Mater. 8, 1702506 (2018). [5] S. Chatterjee, Y. Ie, T. Seo, T. Moriyama, G.-J. A. H. Wetzelaer, P. W. M. Blom, Y. Aso, NPG Asia

Mater. 10, 1016 (2018).

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1 Changing optical properties stepwise from oligomeric to polymeric squaraine dyes

2 -mandatory blank line-

3 Christoph Lambert, Sebastian Völker, Maximilian Schreck, Arthur Turkin

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Institut für Organische Chemie, Universität Würzburg (Germany)

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7 Indolenine squaraine dyes possess narrow absorption bands in the red to near infrared spectral

8 region, high extinction coefficients and high fluorescence quantum yields. These advantageous

9 properties make them ideal for energy transfer processes and also for NIR emitters. We were using

transoid and cisoid indolenine squaraine dyes and linked them covalently to form homo- and hetero-

11 dimers, trimers, larger oligomers and polymers. For specific polymers, depending on the solvent, the

12 formation of stretched and helix foldamers was found. By stepwise synthesis of monodisperse

13 oligomers up to nonamers we could show that the helix formation is also length dependent. The

14 optical properties of these systems are studied by steady-state and fs-time resolved optical

spectroscopy. Depending on the structure we found J- or H-type aggregate excitonic behaviour. The

16 photoinduced dynamics cover the range from exciton relaxation to ultrafast energy transfer

17 processes.

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.. ..... Evidence ;. ,r-~--.... -

T i ., _,,,,..,., "'\ ISC _c-

s, __J;;::: Tn RISC ~ KIC

-r •.•

:=::,::~ EQE :9.13 %

"Hot Exciton" TADF s. ------

Experimental Evidence for “Hot Exciton” Thermally Activated Delayed Fluorescence Emitters

-mandatory blank line-

Ying Wang1,2

-mandatory blank line-1Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, No. 29 Zhongguancun

East Road, Haidian District, Beijing, 100190, P. R. China, 2University of Chinese Academy of Sciences,

Beijing, 100049, P. R. China

-mandatory blank line-

“Hot exciton” thermally activated delayed fluorescence (TADF) emitters are put forward as a new mechanism for the near 100% yield of singlet excitons for OLEDs. However, contradiction

between no effective photophysical experiments and high device results causes the “hot exciton” mechanism to be still a controversial question. Here, we reported three TADF emitters containing

electron-donating 9,9-dimethyl-9H-fluoren and electron-accepting benzo[c][1,2,5]thiadiazole or

difluorobenzo[c][1,2,5]thiadiazole moieties. The steady and transient photophysical characterization

combined with density functional theory (DFT) calculation adequately demonstrate that all the

emitters exhibit TADF via reverse intersystem crossing (RISC) from “hot exciton” triplet excited state. The fast RISC process with “hot exciton” mechanism affords a very short delayed lifetime of the emitters (shorter than 0.6 ms). OLEDs based on these emitters exhibit excellent OLED performance

with high exciton utilization over 25% and the best device shows a maximum current efficiency of

31.02 cd/A, a maximum power efficiency of 27.85 lm/W, and external quantum efficiency of 9.13%,

which are among the best of OLEDs with “hot exciton” mechanism. Importantly, all the devices show very low efficiency roll-off even at high current density due to the fast RISC process via “hot exciton” triplet state and thus short delayed lifetime. This work highlights the TADF emitters with “hot exciton” mechanism for high performance OLEDs with very low efficiency roll-off.

References 1. H. Uoyama, K. Goushi, K. Shizu, H. Nomura, C. Adachi*, Nature 492, 234. (2012). 2. L. Yao, S. Zhang, R. Wang, W. Li, F. Shen, B. Yang*, Y. Ma*, Angew. Chem. Int. Ed. 53, 2119.

(2014). 3. J. Liu, Z. Li, T. Hu, X. Wei, R. Wang, X. Hu, Y. Liu, Y. Yi*,Y. Yamada-Takamura, P. Wang, Y.

Wang*, Adv. Opt. Mater. 1801190. (2018).

Functional π-Electron Systems14th International Symposium on

Abstracts Poster Presentation

Plenary Lectures

Thursday, June 6th

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Two-dimensional π-conjugated Covalent Organic Frameworks (COFs):

Emergence of high charge-carrier mobilities and magnetic properties

Jean-Luc Brédas

School of Chemistry and Biochemistry

Center for Organic Photonics and Electronics

Georgia Institute of Technology

Atlanta, Georgia 30332-0400, USA

In this presentation, we first give a brief introduction to the field of two-dimensional (2D) π-

conjugated covalent organic frameworks (COFs). We describe how the symmetry of the core units

and the lattice influences the nature of the electronic bands at/near the Fermi energy and explain

why these bands, which govern the electrical and optical properties, can go from being totally flat to

being highly dispersive [1].

We then discuss a series of three 2D π-conjugated COFs based on pyrene, porphyrin, and zinc-

porphyrin cores connected via diacetylenic linkers [2]. Their electronic structures are indicative of

valence and conduction bands that have large widths, ranging between 1 and 2 eV. Using a molecular

approach to derive the electronic couplings between adjacent core units and the electron-vibration

couplings, these three π-conjugated 2D COFs are predicted to have ambipolar charge-transport

characteristics with electron and hole mobilities in the range of 65-95 cm2V-1s-1 . Such predicted

values rank these 2D COFs among the highest-mobility organic semiconductors. In addition, the zinc-

porphyrin-based 2D COF was synthesized in the group of Seth Marder at Georgia Tech and

characterized in the group of Will Dichtel at Northwestern, which demonstrates the feasibility of

these electroactive networks.

While the search for 2D organic semimetallic Dirac materials displaying like graphene a Dirac cone at

the Fermi level remains active, attention is also being paid to the quantum phase transition from

semimetal to antiferromagnet. Such a transition in graphene-like materials has been predicted based

on theoretical investigations of the 2D honeycomb lattice; it occurs (within a Hubbard model) when

the on-site electron-electron Coulomb repulsion (U) is much larger than the nearest-neighbor inter-

site electronic coupling (t). Here, we discuss stable radical-carrying monomers and use them as

building blocks to design 2D hexagonal π-conjugated COFs. We evaluate both the nonmagnetic

semimetallic phase and magnetically ordered phases. We find that the electronic coupling between

adjacent radical centers in these COFs is more than an order of magnitude smaller than in graphene

while the on-site Coulomb repulsion is reduced to a lesser extent. The resulting large U/t ratio drives

these COFs into the antiferromagnetic side of the phase diagram. This work provides a first

theoretical evidence of the realization of an antiferromagnetic Mott insulating phase in 2D π-

conjugated COFs and allows us to outline a strategy to achieve quantum phase transitions from

antiferromagnet to spin liquid and to semimetal.

This work is conducted in the framework of the ARO-MURI Center for Advanced 2D Organic

Networks (CATON).

[1] S. Thomas, H. Li, C. Zhong, M. Matsumoto, W.R. Dichtel, and J.L. Brédas, Chem. Mater. (2019).

[2] S. Thomas, H. Li, R.R. Dasari, A.M. Evans, W.R. Dichtel, S.R. Marder, V. Coropceanu, and J.L.

Brédas, Mater. Horizons (2019).

[3] S. Thomas, H. Li, and J.L. Brédas, Adv. Mater. (2019).

Title: Single-molecule label-free large-area bioelectronic sensing of clinical biomarkers

Autor: Luisa Torsi

Abstract: Among the single-molecule detection methods proposed so far, only a few are exploitable for real clinical sensing. Large-area organic-bioelectronics is emerging as a cross-disciplinary research field for the development of a platform capable of selective, label-free and fast biomarker detection at the physical limit in real biofluids. A mass-manufacturable platform with such characteristics holds the potential to bring precision medicine into the everyday medical practice, revolutionizing our current approach to clinical analysis. This lecture aims at critically prioritize the main technologies for single-molecule detection. Scrutinized figures-of-merit include, besides limit-of-detection and selectivity, feasibility of operation in real-fluids, time-to-results and cost-effectiveness. Electrolyte-Gated Field-Effect-Transistors (EG-FETs) [1-4] with a bio-functionalized large-area sensing gate, appear as very promising, also over organic-electrochemical-transistor. The material science and the devices operational aspects underpinning EG-FETs unprecedented sensing performance, including the role of the cooperative hydrogen-bonding network and the gate-channel strong capacitive coupling, are discussed.

1. Macchia, E., Manoli, K., Holzer, B., Di Franco, C., Ghittorelli, M., Torricelli, F., Alberga, D., Mangiatordi, G.F., Palazzo, G., Scamarcio, G., Torsi, L. Single molecule detection with a millimetre-sized transistor. Nature Communications 9, 3223 (2018).

2. Nature highlights - Selections form the scientific literature. Nature 560, 412 (2018). 3. Macchia, E., Tiwari, A., Manoli, K., Holzer, B., Ditaranto, N., Picca, R.A., Cioffi, N., Di Franco,

C., Scamarcio, G., Palazzo, G., Torsi, L. Label-free and selective single-molecule bioelectronic sensing with a millimeter-wide self-assembled monolayer of anti-immunoglobulins. Chemistry of Materials in press (2019)

4. Macchia, E., Manoli, K., Holzer, B., Di Franco, C., Picca, R., Cioffi, N., Scamarcio, G., Palazzo, G., Torsi, L. Selective Single-Molecule Analytical Detection of C-Reactive Protein in Saliva with an Organic Transistor. Analytical and Bioanalytical Chemistry in press (2019).

Functional π-Electron Systems14th International Symposium on

Abstracts Poster Presentation

Invited Lectures

Thursday, June 6th

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Fade to Black: Color ControlinElectrochromic Polymers

John R. Reynolds

School of Chemistry andBiochemistry, School of Materials Scienceand Engineering,CenterforOrganic Photonics and Electronics, Georgia Tech Polymer Network

Georgia Institute of Technology,Atlanta (USA)

Redox active electrochromic polymers (ECPs) are used in a number of absorption/transmission (window type) and reflective (display type)applications. For somedevices (displays, information signs, wearables, etc.) the vibrant color expressed by the polymers is important, while for other devices (windows, E-paper, goggles, glasses,etc.)neutral colorblacks and brown's are ofmore importance. Here, we demonstrate our development of a full color palette of easily scaled electrochromic polymers, which switchbetweena vibrantly coloredneutral state toa highly transmissive oxidized state. Polymerizations are carried out using C-H activated direct arylation of 3,4-dioxythiophene derivatives with a variety of heterocycles, which allows us to tune the UV-Vis spectra across thefull visibleand, thus,have a high degree of color control.Low oxidation potentials provided by the dioxy-substitution yield a family of polymers with polaron/bipolarontransitions in the nearinfrared, thus transmissiveto theeye and yielding high contrastECPs.Treating these ECP's as blendable inks, color mixing is used to yield a fullfamily of secondary colorsalong with broadly absorbing blacks and browns. Tuning the redox switching potential of the component materials allows elimination of intermediate colors as a clear materialcan fully "fade to black".As an alternative approach, random copolymers have been prepared which contain a range of electrochrome's on each chain. Subtle structural changes are used to control intermediate hues within the black states, ultimately allowing true black transmissive switching ECPs with color neutrality throughout the full switch. Switching lifetimes ranging from tens tohundreds of thousands of cycles will be demonstrated.

Energy conversion with synergistic combinations of acenes and quantum dots

In this talk, I will describe energy transfer between semiconductor quantum dots (QDs) and π -

conjugated molecules, focusing on the transmitter ligand at the organic− inorganic interface. Efficient

transfer of triplet excitons across this interface allows photons to be directed for effective use of the

solar spectrum. For example, a photon upconversion system composed of semiconductor QDs as

sensitizers, surface bound organic ligands as transmitters, and molecular annihilators has the

advantage of large, tunable absorption cross sections across the visible and near-infrared

wavelengths. This may allow the near-infrared photons to be harnessed for photovoltaics and

photocatalysis. Here I summarize the progress in this recently reported hybrid upconversion platform

from my group. I will discuss strategies to overcome the bottlenecks with molecular design in terms

of tuning molecular energetics, photophysics, binding affinity, stability, and energy off sets with

respect to the QD donor. Efficient triplet energy transfer in this hybrid platform will find utility in both

up- and down-conversion, with potential for exceeding the Shockley− Queisser limit.

M- L- Tang, University of California, Materials Science & Engineering, Riverside, California, United

States of America

Modeling charge transport and recombination in conjugated polymer

heterojunctions

D. Beljonne, UMONS

We will review recent computational work highlighting that resilience to

conformational motion is the key feature for reduced energy disorder in donor-

acceptor conjugated polymers. Through detailed spectroscopic investigations, we

will show that properly designed amorphous polymers can display high

photoluminescence quantum yields together with high charge carrier mobility. We

use the light emission from exciton states pinned at close-crossing points to study

the interplay between transport and luminescence. Preliminary transport

simulations of conformationally-dressed charge carriers along polymer chains

performed using mixed classical-quantum simulations will be discussed. Finally, if

time permits, we will report on modeling studies of electron-hole recombination in

fullerene and non-fullerene acceptor polymer bulk heterojunctions.

David Beljonne, FNRS Research Director Associate Editor, ACS Applied Materials & Interfaces

Chimie des Matériaux Nouveaux & Centre d'Innovation et de Recherche en Matériaux Polymères Université de Mons - UMONS / Materia Nova Place du Parc, 20, B-7000 MONS (Belgium) Web page: http://morris.umons.ac.be/

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Charge transfer beyond the first monolayer: Fact or Fiction?

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Alexander T. Egger,1 Lukas Hörmann,1 Andreas Jeindl,1 and Oliver T. Hofmann1

-mandatory blank line-1Institute of Solid State Physics, Graz University of Technology, NAWI Graz, Graz (Austria)

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The adsorption of strong organic acceptors on metallic or semiconducting electrodes is a powerful tool

for organic electronics. The charge-transfer reaction between the components gives rise to a interface

dipole. This dipole allows to continuously tune the substrate’s work functions – and, consequently, the

charge-injection barriers – via the adsorbate’s coverage. While for most adsorbates, the charge-

transfer reaction is limited to the molecules in direct contact with the substrate, i.e. the first

(sub)monolayer, for several systems experimental indications for charge-transfer to the second layer

and beyond were found. However, such long-ranged charge transfer is at variance with most

contemporary level-alignment models. This raises the question whether these experimental

indications have been correctly interpreted, requiring level alignment models need to be amended, or

whether a different effect, such as a structural transition, can explain the experimental findings.

In this contribution, we investigate this question exemplarily for tetracyanoethylene (TCNE) adsorbed

on Cu(111). There, vibrational spectroscopy finds evidence for highly charged molecules at low

coverage (sub-monolayer), singly charged molecules

at higher coverage (presumably the second layer),

and uncharged molecules (the bulk material) [1].

Conversely, straightforward density functional theory

(DFT) calculations, performed for the simple

structural model of flat-lying molecules shown in

Figure 1, fail to reproduce the experimental signal for

the singly charged molecule. Therefore, we employ

our recently developed SAMPLE approach [2,3],

which combines DFT with machine learning to scan

the polymorph space of the interface. These

calculations show that the formation of a second layer is in close competition with a reordering of the

molecules in the first layer. This phase transition, which fundamentally alters the properties of the

interface (including the charge state of the molecules in direct contact) satisfactorily explains the

measured signals.

At least for this system, we can thus refute the notion of charge-transfer to molecules without direct

contact to the surface. Our study emphasizes the value of computational support, including first-

principles structure determination, for a comprehensive understanding of the process occurring at

inorganic/organic hybrid interfaces.

[1] W. Erley, H. Ibach, J. Phys. Chem, 91, 2947 (1987)

[2] M. Scherbela, L. Hörmann, A. Jeindl, V. Obersteiner, O. T. Hofmann, Phys. Rev. Mat., 2 (2018)

[3] L. Hörmann, A. Jeindl, A. T. Egger, M. Scherbela, O. T. Hofmann, arxiv: 1181.11702

Figure 1: Naive sturctural model for TCNE on Cu(111)

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1 Smallmolecule designfor organic electronics 2 -mandatory blank line-3 John E. Anthony1

4 -mandatory blank line 1Department of Chemistry, University of Kentucky, Lexington (USA)

6 -mandatory blank line-7 The performance of organic materials in thin-film electronics is related primarily to their solid-8 state intermolecular interactions. We have shown a simple series of functionalization strategies that 9 allow the fine-tuning of these interactions, and have iteratively expanded and applied these

strategies to an array of aromatic chromophores. More recently, we have demonstrated the impact 11 of disorder on electronic performance, and devised general guidelines to minimize disorder to 12 improve charge transport. Currently, we show the impact of thermally induced vibrations on charge 13 transport properties, and exploited strategies to reduce the impact of these vibrations, enhancing 14 charge transport properties by another order of magnitude. Alternative functionalization schemes

are required to study and exploit photonic properties, in areas such as bio-imaging and singlet 16 fission, generating another set of design principles we use to prepare high-performance small 17 molecules. This talk will highlight the myriad ways synthetic chemists can play an important role in 18 the advancement of organic electronics.

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Rational Strategies to Stabilize the Morphology of Non-Fullerene Organic Solar Cells Harald Ade*

E-mail: hwade@ncsu.edu

Organic photovoltaics (OPVs) are considered one of the most promising cost-effective options for utilizing solar energy. Recently, the OSC field has been revolutionized by the development of novel non-fullerene small molecular acceptors. With efficiencies now reaching 14% in many systems, the device stability and mechanical durability of non-fullerene OPVs have received less attention. Developing devices with both high performance and long-term stability remains challenging, particularly if the material choice is restricted by roll-to-roll and benign solvent processing requirements and desirable mechanical durability. Furthermore, many reports of OSC blends focus primarily on the device performance aspect of the solar cell and ignore the mechanical durability, which is an important consideration for OPV commercialization. Here we review the thermodynamic and kinetic factors and their interrelation that underlay morphological stability. We outline rational strategies to design nonfullerene binary and ternary OPVs that exhibit improved thermal stability and storage stability. Our results indicate that ductile systems, not surprisingly, are less stable. This implies competing engineering requirements if highly stretchable and bendable devices and stability are desired at the same time.

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Tuning Transport and Emission Properties of Polymer-Sorted Carbon Nanotube Networks

Jana Zaumseil1,2

1 Institute for Physical Chemistry, Universität Heidelberg, Heidelberg (Germany)

2 Centre for Advanced Materials, Universität Heidelberg, Heidelberg (Germany)

Large volumes of highly purified dispersions of semiconducting (6,5) single-walled carbon nanotubes

are readily available through polymer-wrapping and shear-force mixing [1]. They enable the

deposition (e.g. by aerosol jet printing) of semiconducting nanotube layers of variable thickness from

sparse networks to 300 nm thick films with large optical density. These layers can be applied in

printed field-effect transistors [2] with excellent device performance, but also as electrochromic

notch filters [3], for light-emitting diodes in the near-infrared [4] and photovoltaic cells [5] very

similar to widely used conjugated polymers [6]. Charge transport and light emission depend on

network composition, temperature [7], different dielectric environments and dopant

concentrations [8], and can be tuned with light-switchable dipoles, via introduction of sp3-defects

and with responsive wrapping polymers. A few of these examples will be presented and discussed in

terms of insights into the network properties of sorted carbon nanotubes and their practical

applications.

References

[1] Graf et al., Carbon 105, 593 (2016).

[2] Rother et al., Adv. Electron. Mater. 3, 1700080 (2017).

[3] Berger et al., ACS Appl. Mater. Interfaces 10, 11135 (2018).

[4] Graf et al., Adv. Mater. 30, 1706711 (2018).

[5] Classen et al. Adv. Energy Mater. 9, 1801913 (2018).

[6] Zaumseil, Adv. Electron. Mater. 1800514 (2018).

[7] Brohmann et al., J. Phys. Chem. C 122, 19886 (2018).

[8] Schneider et al. ACS Nano 12, 5895 (2018).

Taming complexity in polymer opto-electronics: tailoring multifunctional devices and chemical sensors

Paolo Samorì

ISIS, Université de Strasbourg & CNRS, 8 allée Gaspard Monge, 67000 Strasbourg, France.

One among the greatest challenges in organic electronics is the fabrication of multifunctional devices, i.e. that can respond to multiple and independent stimuli. Such a challenge can be accomplished by developing multicomponent materials in which each component imparts a well-defined function to the ensemble. The controlled combination of such components and their integration in real devices can be achieved by mastering the supramolecular approach. In my lecture I will review our recent works on the combination of carbon-based nanomaterials, in particular organic semiconductors, with photochromic molecules (diarylethenes or azobenzenes) in order to realize smart, high-performing and light-sensitive (opto)electronic devices as well as flexible non-volatile optical memory thin-film transistor device with over 256 distinct levels. The developed knowledge is of high relevance also for the fabrication of chemical sensors possessing sensitivities, selectivities, response speeds and reversibilities beyond the state-of-the-art.

References [1] For reviews see: (a) X. Zhang, L. Hou, P. Samorì, Nat. Commun. 2016, 7, 11118. (b) E. Orgiu, P. Samorì, Adv. Mater. 2014, 26, 1827-1845. [2] For modulating charge injection at metal-organic interface with a chemisorbed photochromic SAM see: (a) N. Crivillers, E. Orgiu, F. Reinders, M. Mayor, P. Samorì, Adv. Mater. 2011, 23, 1447-1452. (b) T. Mosciatti, M.G. del Rosso, M. Herder, J. Frisch, N. Koch, S. Hecht, E. Orgiu, P. Samorì, Adv. Mater. 2016, 28, 6606. [3] For hybrid structure combining organic semiconductors blended with Au nanoparticles coated with a photochromic SAM see: C. Raimondo, N. Crivillers, F. Reinders, F. Sander, M. Mayor, P. Samorì, Proc. Natl. Acad. Sci. U.S.A. 2012, 109, 12375-12380. [4] For blends energy level phototuning in a photochromic - organic semiconductor blend see: (a) E. Orgiu, N. Crivillers, M. Herder, L. Grubert, M. Pätzel, J. Frisch, E. Pavlica, G. Bratina, N. Koch, S. Hecht, and P. Samorì, Nat. Chem. 2012, 4, 675-679. (b) M. El Gemayel, K. Börjesson, M. Herder, D.T. Duong, J.A. Hutchison, C. Ruzié, G. Schweicher, A. Salleo, Y. Geerts, S. Hecht, E. Orgiu, P. Samorì, Nat. Commun. 2015, 6, 6330. [5] For optically switchable light-emitting transistors: L. Hou, X. Zhang, G.F. Cotella, G. Carnicella, M. Herder, B.M. Schmidt, M. Pätzel, S. Hecht, F. Cacialli, P. Samorì, "Optically switchable organic light-emitting transistors", Nat. Nanotech. 2019 in press (DOI: 10.1038/s41565-019-0370-9) [6] For the fabrication of memory devices: T. Leydecker, M. Herder, E. Pavlica, G. Bratina, S. Hecht, E. Orgiu, P. Samorì, Nat. Nanotech. 2016, 11, 769–775. [7] For the novel nanomesh scaffold based photodetector: L. Zhang, X. Zhong, E. Pavlica, S. Li, A. Klekachev, G. Bratina, T.W. Ebbesen, E. Orgiu, P. Samorì, Nat. Nanotech. 2016, 11, 900–906. [8] For chemical sensors: (a) M.A. Squillaci, L. Ferlauto, Y. Zagranyarski, S. Milita, K. Müllen, P. Samorì, Adv. Mater. 2015, 27, 3170-3174. (b) M.-A. Stoeckel, M. Gobbi, S. Bonacchi, F. Liscio, L. Ferlauto, E. Orgiu, P. Samorì, Adv. Mater. 2017, 29, 1702469.

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Chiral Carbon Architectures

Linda Bannwart, 1 Rajesh Mannancherry, 1 Kevin Weiland,1 Thomas Brandl, 1 Michel Rickhaus,1 Tomas Solomek, 1 Michal Juricek,1 Marcel Mayor1-3

1Department of Chemistry, University of Basel, Basel (Switzerland); 2Institute of Nanotechnology, KIT,

Karlsruhe (Germany); 3LIFM, School of Chemistry, Sun Yat-Sen University, Guangzhou (China)

Helical chiral π-systems can been classified by the spatial relationship between their aromatic subunits and their axles [1]. The atrop-isomeriztion of (1,1’)-bi-phenyl systems stabilized by additional alkyl bridges interlinking the 2,2’ posi-tions [2,3], awoke our interest in the stabilization of helically arranged π-systems. The dimensional mismatch of two tightly fixed oligomer chains was predicted to result in the helical wrapping of the expanded subunit around the more compact one. And indeed, in a first model compound the longer benzylic ether oligomer entwined helically around the oligophenyl back-bone [4,5]. The influence of the interlinking heteroatom in the benzylic ether on the extent of helicity was studied [6]. In the latest approach, we even got rid of the heteroatoms. These first all carbon “Geländer”-structures consist of a para-ethanyl-phenyl subunit fixed to a para-terphenyl backbone [7]. While these design concepts are of fundamental interest for helical architectures, helical “Geländer”-structures with delocalized π-systems as banisters might display more interesting electronic properties. In a first attempt, the size-mismatch approach was applied to a dialkyne interlinked phenyl banister. While a first model compound corroborates the molecular design, it also displayed the increased reactivity of the bent dialkyne subunit [8]. An alternative molecular design to helicity consist of the integration of a step into a macrocycle, resulting in larger coils with smaller step heights. In a first approach, a [2,2]-paracyclophane was integrated as step into an oligothiophene [9]. Fast enantiomerization was observed for the flexible macrocycle. To increase the enantiomerization barrier two additional rod-like substituents were attached to the [2,2]-paracyclophane. And indeed, due to the steric fixation both enantiomers could be separated and their enantiomerization was analyzed [10]. Yet another strategy profits from the templation of the macrocycles subunit in metal complexes. The demonstration of the concept was achieved by interlinking two alkyne-decorated terphenyl ligands fixed in the octahedral coordination sphere of an Fe(II) ion [11]. However, the chiral arrangement of the ligand is only maintained in the complex.

[1] M. Rickhaus, M. Mayor, M. Juricek, Chem. Soc. Rev. 45, 1542-1556 (2016). [2] J. Rotzler, H. Gsellinger, A. Bihlmeier, M. Gantenbein, D. Vonlanthen, D. Häussinger, W. Klopper, M. Mayor, Org.

Biomol. Chem. 11, 110-118 (2013). [3] A. Bihlmeier, J. Rotzler, M. Rickhaus, M. Mayor, W. Klopper, Phy. Chem. Chem. Phys. 17, 11165-11173 (2015). [4] M. Rickhaus, L. M. Bannwart, M. Neuburger, H. Gsellinger, K. Zimmermann, D. Häussinger, M. Mayor, Angew. Chem. Int. Ed. 53, 14587-14591 (2014). [5] M. Rickhaus, L. M. Bannwart, O. Unke, H. Gsellinger, D. Häussinger, M. Mayor, Eur. J. Org. Chem.

786-801 (2015). [6] M. Rickhaus, O. Unke, R. Mannancherry, L. M. Bannwart, M. Neuburger, D. Häussinger, M. Mayor, Chem. Eur. J. 21, 18156-18167 (2015). [7] R. Mannancherry, M. Rickhaus, D. Häussinger, A. Prescimone, M. Mayor, Chem. Sci. 9 5758-5766 (2018). [8] L. M. Bannwart, L. Jundt, T. Müntener, M. Neuburger, D. Häussinger, M. Mayor, Eur. J. Org. Chem. 3391-3402 (2018). [9] K. J. Weiland, N. Münch, W. Gschwind, D. Häussinger, M. Mayor, Helv. Chim. Acta 102, e18002 (2019). [10] K. J. Weiland, T. Brandl, K. Atz, A. Prescimone, D. Häussinger, T. Solomek, M. Mayor, J. Am.

Chem. Soc. 141, doi: 10.1021/jacs.8b11797 (2019). [11] T. Brandl, V. Hoffmann, A. Pannwitz, D. Häussinger, M. Neuburger, O. Fuhr, S. Bernhard, O. S. Wenger, M. Mayor, Chem. Sci. 9, 3837-3843 (2018).

Nature of Photogenerated Defects in Bulk Heterojunction OPVs

Joshua Wolanyk,1,2,3 Raghunandan B-Iyer,3,4 Joseph Shinar,1,2 and Ruth Shinar3,4

1Physics & Astronomy Department, Iowa State University, Ames, IA 50011

2Ames Laboratory, USDOE, Iowa State University, Ames, IA 50011

3Microelectronics Research Center, Iowa State University, Ames, IA 50011

4Electrical & Computer Engineering Department, Iowa State University, Ames, IA 50011

Abstract

Intrinsic photodegradation of organic solar cells, particularly bulk heterojunction (BHJ), remains

a key commercialization barrier. Two types of photogenerated defects in BHJ films and related

systems have recently been explored via electron paramagnetic resonance (EPR): (a) deeply

trapped holes and electrons in polyelectrolyte-fullerene assemblies [1] and (b) carbon dangling

bonds (C DBs) [2]; the latter were invoked in support of simulations [3,4]. In both cases, the

generated EPR defect signature observed in photodegraded films weakens over several days.

This talk will present new results of broadly examined various donor/acceptor structures,

including of BHJ blend films with a non-fullerene acceptor, to obtain a comprehensive

understanding of photodegradation. Evidence for C DBs vs deeply trapped holes and electrons

will be discussed, given that the defects are generated largely by blue/UV irradiation rather than

longer wavelengths. This observation clearly supports C DB formation over deeply trapped

charges. The role of “hot” polarons in donor:acceptor interface C DB formation will also be

discussed.

[1] R. C. Huber et al., Science 348, 1340 (2015).

[2] F. Fungura et al., Adv. Ener. Mater. 7, 1601420 (2017).

[3] J. E. Northrup, Appl. Phys. Express 6, 121601 (2013).

[4] S. Shah and R. Biswas, J. Phys. Chem. C 119, 20265 (2015).

Functional π-Electron Systems14th International Symposium on

Abstracts Poster Presentation

Contributed Lectures

Thursday, June 6th

R R H

~ N

ICT'e~) s TP

Known polymer types R R R R

AA + - .l4. poly(TP) poly(O-TP)

New design paradigm R R H

A

. + n poly(TP-A)

1 Ambipolar‐Acceptor Frameworks as a New Design Paradigm in Low Bandgap Polymers 2 ‐mandatory blank line‐3 Evan W. Culver

1, Trent E. Anderson

1, Wyatt D. Wilcox

1, Irene Badía‐Domínguez

2, M. Carmen Ruiz

4 Delgado2, and Seth C. Rasmussen

1

5 ‐mandatory blank line‐6 1

Department of Chemistry and Biochemistry, North Dakota State University, Fargo (USA) 7 2

Department of Physical Chemistry, University of Málaga, Málaga (Spain). 8 ‐mandatory blank line‐9 Significant effort has been applied to the development of design principles for the production of low

10 bandgap (Eg < 1.5 eV) materials, which play critical roles in applications such as organic photovoltaics 11 and photosensors [1]. While a number of factors are known to contribute to the Eg of conjugated 12 materials, only two general design approaches have been successfully applied to the generation of 13 low Eg materials. These include the use of fused‐ring thiophenes to enhance the quinoidal nature of 14 the backbone and application of donor−acceptor (D−A) frameworks, the second of which has become 15 a critical design factor in the generation of low and reduced (Eg = 1.5‐2.0 eV) bandgap materials [1]. 16 Such D‐A frameworks are based on a regular alternation of electron‐rich (donor) and electron‐poor 17 (acceptor) groups, with the lower Eg explained by hybridization of the frontier orbitals, thus giving a D‐A 18 material with HOMO levels characteristic of the donor and LUMO levels characteristic of the acceptor 19 [1]. Still, this model was originally demonstrated in a minor class of conjugated materials and has been 20 applied since to all conjugated materials without further refinement. As a result, various assumptions 21 about this approach have become prevalent, the most basic of which is that monomers act exclusively 22 as donors, acceptors, or neutral 'spacers'. However, a class of acceptors, thieno[3,4‐b]pyrazines (TPs, 23 Figure 1), have now been shown to also exhibit properties of very strong donors comparable to 3,4‐24 ethylenedioxythiophene (EDOT) [2]. As TPs act simultaneously as both acceptors and donors, such units 25 have been designated ambipolar units [2‐4]. Thus, TPs contribute to both the HOMO and LUMO in D‐A 26 frameworks and it is the internal D‐A interaction of TPs that dominate the electronics of their materials.

27 28 Figure 1. Ambipolar thieno[3,4‐b]pyrazine (TP) and its corresponding polymeric materials.

29 To date, TPs have been utilized in either homopolymers or as acceptors in D‐A frameworks to give 30 low Eg materials. However, as TPs also exhibit a high‐lying HOMO, this should allow for a new design 31 model in which ambipolar units such as TP are paired with an acceptor, rather than the traditional 32 pairing with a donor. Several such ambipolar‐acceptor frameworks have now been successfully pro‐33 duced via direct arylation polymerization (DArP) to give materials with Eg values of 0.97‐1.07 eV [3,4]. 34 The synthesis of such ambipolar‐acceptor frameworks will be presented along with their optical and 35 electronic characterization. Via a combination of experimental data and computational modeling, the 36 fundamentals of this new design paradigm will also be discussed to allow its broader application. 37 38 [1] S. C. Rasmussen. In Encyclopedia of Polymeric Nanomaterials, K. Muellen, S. Kobayashi, Eds.; 39 Springer: Heidelberg, 1155‐1166 (2015). 40 [2] L. Wen, C. L. Heth, and S. C. Rasmussen. Phys. Chem. Chem. Phys. 16, 7231‐7240 (2014). 41 [3] E. W. Culver, T. E. Anderson, J. T. L. Navarrete, M. C. R. Delgado, and S. C. Rasmussen. ACS Macro 42 Lett. 7, 1215‐1219 (2018). 43 [4] T. E. Anderson, E. W. Culver, F. Almyahi, P. C. Dastoor, and S. C. Rasmussen. Synlett 29, 2542‐2546 44 (2018).

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(/) c ::, 0 u

R= H R= Ph R= Meo R= Me R= tBu G2B PhG2B MeOG2B MeG2B 1BuG2B

- tBuG2B

10' - MeG2B - PhG2B - MeOG2B

10'

1~ L.l- -'-------'---L--'-'.n__,u....,.>L_>'-'----'-lll-~ 0 2

101 ••• ~ .. • • •

4 6 Time (µs)

8 10

l 10° • w 0 w •

• tBuG2B 10-1 • MeG2B

• Me0G2B • PhG2B

10·2 ......... ~~~=~~~~~~~

10·3 10·2 10·1 10° 101 102

Current density (mA/cm2)

Thermally‐Activated Delayed‐Fluorescence Dendrimers that Realizes OLEDs with Fully Solution‐Processed Organic‐Layers

‐mandatory blank line‐Ken Albrecht1,2, Kenichi Matsuoka1, Katsuhiko Fujita1, Kimihisa Yamamoto3,4

‐mandatory blank line‐1Institute for Materials Chemistry and Engineering, Kyushu University, Fukuoka (Japan)

2JST‐PRESTO, Kyushu University, Kawaguchi (Japan) 3Laboratory for Chemistry and Life Science, Tokyo Institute of Technology, Yokohama (Japan)

4JST‐ERATO, Tokyo Institute of Technology, Yokohama (Japan) ‐mandatory blank line‐

The development of emitting materials for OLEDs has started with fluorescence, moved to phosphorescence, and recently reached thermally activated delayed fluorescence (TADF). TADF has the advantage of a high internal quantum efficiency (up to 100%) and low cost. We previously revealed that simple carbazole dendrimers have an outer‐layer electron rich potential gradient, i.e., a LUMO at the inner layer, and the HOMO at the outer‐layer [1]. Based on this unique electronic structure, we have proved that carbazole dendrimers with appropriate acceptor (triazine [2] or benzophenone [3]) expresses efficient TADF. We now report terminal modified TADF active carbazole dendrimers that are suitable for efficient OLEDs with fully solution‐processed organic layers.

New TADF active second generation benzophenone core carbazole dendrimers were synthesized (Fig.1). The PLQY of the neat film of tBuG2B [4] was 0.74 and the temperature dependent PL life time measurement revealed that the emission has contribution of TADF (Fig.2). The OLED devices (ITO/ PEDOT:PSS/ PVK/ Dendrimer/ SPPO13/ LiF/ Al) with fully solution processed organic layers exhibited green emission with the maximum external quantum efficiency (EQE) of 17.0 % (Fig.3). It is indicating that the dendrimer is harvesting the electrically‐generated triplet excitons through TADF process. Thus, carbazole‐benzophenone dendrimers are TADF molecules for efficient OLEDs with fully solution processed organic layers, and in our knowledge, the EQE of this device is the highest as this kind of TADF OLED devices [5]. References [1] K. Albrecht, K. Yamamoto, J. Am. Chem. Soc. 131, 2244 (2009). [2] K. Albrecht, K. Matsuoka, K. Fujita, K. Yamamoto, Angew. Chem. Int. Ed. 54, 5677 (2015). [3] K. Matsuoka, K. Albrecht, K. Yamamoto, K. Fujita, Sci. Rep. 7, 41780 (2017). [4] B. Huang, X. Ban, K. Sun, Z. Ma, Y. Mei, W. Jiang, B. Lin, Y. Sun, Dyes Pigm., 133, 380 (2016). [5] K. Matsuoka, K. Albrecht, A. Nakayama, K. Yamamoto, K. Fujita, ACS Appl. Mater. Interfaces, 10 33343 (2018).

Fig.1 Structure of carbazole‐benzophenone dendrimers.

Fig.2 PL decay curve of TADF dendrimer neat films at 300 K.

Fig.3 External quantum efficiency‐ current density characteristics of theOLED device with terminal substituetd carbazole‐benzophenone dendriemr as an emitting layer.

C12H25 Q--~ ~'N~ o-s' ~ ~ ~'o

~-y-Qr~ ,N ~ II s

H2sC12 O-~, F 0

BAz-H BAz-M1

N ~,, 11 C12H2s ,, I \ S ,N ~ II S ~ /, n 0-B ~'o H2sC12

P-BAz

Mn= 21,400 Mw = 55,600 Mw!Mn = 2.59

M~O C12H2s N _ r, 11 ~ I \ S N

OMe ~ II S ~ /, n

H2sC12 P-Az

BAz•H BAz-M1 BAz-M2 P-BAz

300 400 500 600 700 800 900 Wavelength / nm

550

Mn= 20,900 Mw = 52,100 Mw!Mn = 2.50

650 750 850 Wavelength I nm

950

Near-Infrared-Emissive Conjugated Polymers Based on Fused Azobenzene Complexes

Masayuki Gon, Kazuo Tanaka, Yoshiki Chujo

Department of Polymer Chemistry, Graduate School of Engineering, Kyoto University, Kyoto (Japan)

Abstract Heteroatoms have received a great deal of attention because of the potential to add unique characteristics of elements to carbon-based materials. Azobenzene, which includes a nitrogen– nitrogen double (N=N) bond in the structure, is a well-known scaffold showing photoisomerization. However, it is scarcely known that azobenzene has high electron affinity. Additionally, azobenzene is hardly used as a framework of π-conjugated polymers due to the photoisomerization. Therefore, electronic properties of azobenzene have not been clarified completely. Recently, it was reported that azobenzene exhibited good luminescence with a B–N coordination which inhibited the photoisomerization and changed electronic conditions of azobenzene.[1] This strategy suggests that azobenzene has a potential to be a new scaffold for π-conjugated polymers. In this research, we prepared a new boron-fused azobenzene (BAz) scaffold and applied it to π-conjugated polymers.[2]

Figure 1. Structures of the compounds.

Figure 1 shows the structures of the (A) (B) synthesized compounds in this research. From the result of UV–vis absorption and photoluminescence (PL) spectra (Figure 2), it was suggested that π-conjugated system was extended via N=N bonds. Surprisingly, as the π-conjugated system was expanded, the PL peak tops were gradually red-shifted and the absolute PL quantum efficiencies (ΦPL) of the BAz derivatives were enhanced. In particular, P-BAz showed highly efficient Figure 2. (A) UV–vis absorption spectra and (B) PL

near-infrared (NIR) emission (λPL = 751 nm, spectra of BAz-H, BAz-M1, BAz-M2 and P-BAz in

ΦPL = 0.25 in toluene). This is because of the toluene (1.0×10−5 M). low lowest unoccupied molecular orbital (LUMO) energy level and the ring-fused structure derived from the B–N coordination. Boron coordination was necessary for showing high PL performances because P-Az, which is a pristine azobenzene-based polymer, exhibited no emission. These results indicate that the N=N bond is expected to be used for a new class of skeletons for creating luminescent π-conjugated materials.

[1] J. Yoshino, N. Kano and T. Kawashima, Chem. Commun. 0, 559 (2007). [2] M. Gon, K. Tanaka and Y. Chujo, Angew. Chem. Int. Ed. 57, 6546 (2018).

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Cz ct Cz=-No

1Bu

Phosphorescent organometallic dendrimers for non-doped organic light-emitting diodes

Shigeyuki Yagi, Naoki Okamura, and Takeshi Maeda

Department of Applied Chemistry, Graduate School of Engineering, Osaka Prefecture University,

Sakai, Osaka (Japan)

Organic light-emitting diode (OLED) has been attracting much attention from the viewpoint of application to flat panel displays and solid-state lightings. The solution processed device fabrication is expected to provide opportunities to obtain OLEDs at lower cost than the vacuum processing. A wide range of materials, from low-mass molecules to polymers, are used in solution-processed OLEDs. We have so far developed phosphorescent organoplatinum(II) and organoiridium(III) complexes showing excellent photoluminescence properties [1]. We are currently interested in solution-processed, non-doped OLEDs in which the emitting layer consists of only an emitting material. Towards fabrication of this type of devices, we have been developing phosphorescent organometallic dendrimers bearing charge carrier-transporting dendrons. In this context, we have developed phosphorescent bis- and tris-cyclometalated iridium(III) complexes with hole-transporting dendrons [2].

For example, Ir-1 (Figure 1) consists of our 5‘-benzoylated blue phosphorescent bis-cyclometalated iridium(III) complex [3] attached with a partial structure of our carbazole-based hole-transporting material [4]. The dendritic structure has a significant effect on suppressing aggregate-based emission even in the thin film state, and thus blue emission from the core complex is observed. Using Ir-1

as an emitting layer, a simple non-doped OLED (device structure; ITO (anode)/PEDOT:PSS/Ir-1/CsF/Al (cathode)) was fabricated. The obtained device showed a relatively low maximum external quantum efficiency (EQEmax) less than 1%. To improve the device performance, we fabricated a multilayered, non-doped device by solution processing, the device structure of which is ITO (anode)/PEDOT:PSS/poly(9-vinylcarbazole) (PVCz)/Ir-1/[1,1‘:3‘,1‘‘-terphenyl]-4,4‘‘-diylbis(diphenylphosphine oxide) (BPOPB)/CsF/Al (cathode)). We found that Ir-1 is soluble in cyclohexane and insoluble in lower alcohols. On the other hand, PVCz is soluble in toluene and insoluble in cyclohexane, and BPOPB is soluble in lower alcohols. Thus, we employed an orthogonal solvent system of toluene‒cyclohexane‒2-propanol to prepare the PVCz/Ir-1/BPOPB stacked film. When the hole- and electron-transporting layers (PVCz and BPOPB, respectively) were placed on the anode and cathode sides of the emitting layer, respectively, better device performance was obtained and EQEmax was improved to 5.7%. In the presentation, the development of an ambipolar organoiridium(III) dendrimer for multilayered, non-doped OLED will also be reported.

[1] H. Tsujimoto, S. Yagi, S. Ikawa, H. Asuka, T. Maeda, H. Nakazumi, and Y. Sakurai, J. Organomet.

Chem. 695, 1972 (2010); S. Ikawa, S. Yagi, T. Maeda, H. Nakazumi, H. Fujiwara, and Y. Sakurai, Dyes

Pigm. 95. 695 (2012); T. Shigehiro, S. Yagi, T. Maeda, H. Nakazumi, H. Fujiwara, and Y. Sakurai, J. Phys.

Chem. C 117, 532 (2013); T. Shigehiro, Q. Chen, S. Yagi, T. Maeda, H. Nakazumi, and Y. Sakurai, Dyes

Pigm. 124. 165 (2016). [2] N. Okamura, T. Maeda, and S. Yagi, New. J. Chem. 41, ,10357 (2017). [3] N. Okamura, T. Nakamura, S. Yagi, T. Maeda, H. Nakazumi, H. Fujiwara, and S. Koseki, RSC Adv. 6, 51435 (2016). [4] N. Okamura, H. Funagoshi, S. Ikawa, S. Yagi, T. Maeda, and H. Nakazumi, Mol. Cryst. Liq. Cryst. 621, 59 (2015).

Figure 1. Structure of Ir-1.

Theoretical Study of the Energy Loss Mechanisms for Organic Photovoltaics

Yuanping Yi1

1Institute of Chemistry Chinese Academy of Sciences, Beijing 100190, China

Compared with inorganic and perovskite solar cells, the energy losses in organic solar cells are relatively much large, which severely prevents further improving the power conversion efficiencies of organic photovoltaics. Thus it is highly desirable to elucidate the energy loss mechanisms and influential factors. We have theoretically investigated the excited decay of electron donors and acceptors and the charge recombination process at the donor/acceptor interface to reveal the energy loss pathways in organic solar cells and the important impact of molecular structures and interface geometries. This would be very helpful to reduce energy losses for organic photovoltaics.

λS1: vibrational relaxation ΔGCT: driving force ΔECR: recombination loss

kr: radiative decay rate knr: non-radiative decay rate

FC

S1CT

S0

absorption

λS1

ΔGED

knrkr knrkr

ΔECR

Voltage

loss

Current

loss

charge

migration &

collection

Figure 1. Energy loss pathways in organic solar cells.

[1] L. Zhu, Y. Yi, Z. Wei, J. Phys. Chem. C 122, 22309-22316 (2018). [2] G. Han, Y. Guo, X. Ma, Y. Yi, Solar RRL 2, 1800190 (2018). [3] R. Duan, Q. Peng, X. Shen, G. Han, Y. Guo, Y. Zeng, Y. Yi, J. Phys. Chem. C 122, 3748-3755 (2018). [4] G. Han, Y. Yi, Adv. Theory Simul. 1, 1800091 (2018). [5] G. Han, Y. Guo, R. Duan, X. Shen, Y. Yi, J. Mater. Chem. A 5, 9316-9321 (2017). [6] J. Liu, Y. Zhang, P. Bao, Y. Yi, J. Chem. Theory Comput. 13, 843-851 (2017).

Ladder Polymers made of Pentacyclic Building Blocks linked by Exocyclic Double Bonds

Dr. Ullrich Scherf

Bergische Universität Wuppertal, Macromolecular Chemistry Group (buwmakro) and Institute for

Polymer Technology, Gauss-Str. 20, D-42119 Wuppertal, Germany.

Abstract

Reductive dehalogenation polycondensation of a series of pentacyclic, bisgeminal tetrachlorides with

dicobalt octacarbonyl leads to the formation of homopolymers and copolymers with very different

optical spectra. While the formation of tetrabenzoheptafulvalene connectors introduces efficient

conjugation barriers due to their strongly folded structure, linking of 5-membered ring-based pentacyclic

building blocks via bifluorenylidene connectors allows for an extended -conjugation along the main

chain. A comparison of a homopolymer made from a “mixed” monomer that contains

dichloromethylenes that are incorporated into one 5- and one 7-membered ring with a copolymer made

from a 1:1 mixture of difunctional monomers that contain dichloromethylenes as part of two 5- or 7-

membered rings indicates a quite different reactivity of the dichloromethylene functions if incorporated

into 5- or 7-membered rings. Interestingly, all investigated (co)polymers show an intrinsic microporosity

in their solid state (forming so-called Conjugated Polymers of Intrinsic Microporosity C-PIMs) with the

higher values for polymers containing the distorted bifluorenylidene connectors, reaching a SBET value of

>700 m²/g for the homopolymer poly(indenofluorene). This value is one of the highest values reported

until now for C-PIMs.

::AAAA:: ~ -

Fusing GNRs

1 On-Surface Synthesis of 8- and 10-Armchair Graphene Nanoribbons 2 -mandatory blank line-3 Kewei Sun1, Haiming Zhang1, Lifeng Chi1

4 -mandatory blank line-5 1 Institute of Functional Nano & Soft Materials (FUNSOM), Soochow University, Suzhou 215123,

6 People’s Republic of China

7 -mandatory blank line-8 Armchair graphene nanoribbons (AGNRs) with 8, 10 carbon atoms in width (8- and 10-AGNRs) are 9 synthesized on Au (111) surfaces via lateral fusion of nanoribbons that belong to different

10 subfamilies. Poly-para-phenylene (3-AGNR) chains are pre-synthesized as ladder ribbons on Au (111). 11 Subsequently synthesized 5- and 7-AGNRs can laterally fuse with 3-AGNRs upon annealing at higher 12 temperature, producing 8- and 10-AGNRs, respectively. The synthetic process, their geometric and 13 electronic structures are characterized by scanning tunneling microscope/spectroscope (STM/STS). 14 STS investigations reveal the band gap of 10-AGNR (2.0 ± 0.1 eV) and a large apparent band gap of 8-15 AGNRs (2.3 ± 0.1 eV) on Au (111) surface. 16 17 18

19 20 21 22 23 24 25 26 27 28 29 30

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Chlorination: A Facile Method for Efficient Solar Conversion Feng He*

Department of Chemistry, Southern University of Science and Technology, 1088 Xueyuan Blvd. Shenzhen, 518055, China

With the development of material engineering, interface modification, and advanced device processing in past decades, the power conversion efficiency (PCE) of the state-of-the-art PSCs has already exceeded 13% at present. Especially, the benzothidiazole-T4 families of polymers, such as PffBT4T-2OD, have attracted tremendous research interest in academic communities since they can be processed into highly efficient fullerene/polymer solar cells with power conversions up to 10%. Herein, we designed and synthesized a chlorinated polymer donor, PBT4T-Cl, in which a chorine atom had been introduced at the middle thiophene unit to fine tune the energy level of the final polymers. Compared with its non-chlorinated analog, the PBT4T-Cl-based devices exhibited clear increases in open-circuit voltage and fill factor, achieving PCEs up to 11.18%, which is the highest PCE of a chlorine-based PSC reported to date. GIWAXS analysis illustrated the strong crystallinity from the blend films, AFM and TEM measurements both revealed an optimized morphology of the spin-coated PBT4T-Cl blend films, all of which supported that chlorine substitution could promote the performance of PSCs. More importantly, the PBT4T-Cl-based devices showed superior stability, with a PCE of 8.16% after 50 days device storage, while the non-Cl-analog-based devices remained at only 5.36% in a parallel experiment. Through this research, the chlorination of low band gap polymers provides new insight into designing π-conjugated polymer semiconductors and realizing further enhancement of polymer solar cell efficiency as well as stability.

Fig. 1 The polymer structure, GIWAXS patterns of PBT4T-Cl:PC71BM blend film and its out-of-plane cut profiles, TGA of PffBT4T-2OD and PBT4T-Cl and the Performance parameters of unencapsulaes devices store in glove box.

References 1. H. Chen, Z. M. Hu, H. Wang, L. Z. Liu, P. J. Chao, J. F. Qu, A. H. Liu, W. Chen, F. He*,

Joule, 2018, 2, 1623–1634. 2. D. Z. Mo, H. Wang, H. Chen, S. W. Qu, P. J. Chao, Z. Yang, L. L. Tian, Y. Su, Y. Gao,

B. Yang, W. Chen*, F. He*, Chem. Mater., 2017, 29, 2819–2830

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Chasing the ‘killer’ phonon mode for the rational design of low disorder, high mobility

molecular semiconductors

Guillaume Schweicher1, Gabriele D'Avino2, Michael T. Ruggiero3, J. Axel Zeitler3, Simone Fratini2,

Henning Sirringhaus1

1Optoelectronics Group/Cavendish Laboratory, University of Cambridge, Cambridge (United-Kingdom) 2Institut Néel-CNRS and Université Grenoble Alpes, Grenoble (France)

3Department of Chemical Engineering and Biotechnology, University of Cambridge, Cambridge

(United-Kingdom)

Molecular vibrations play a critical role in the charge transport properties of weakly van der Waals

bonded organic semiconductors [1-4]. To understand which specific phonon modes contribute most

strongly to the electron – phonon coupling and ensuing thermal energetic disorder in some of the

most widely studied high mobility molecular semiconductors we have combined experimental

measurements of the low-frequency vibrations using inelastic neutron scattering and terahertz time-

domain spectroscopy with state-of-the-art quantum mechanical simulations of the vibrational modes

and the ensuing electron phonon coupling constants. In this way we have been able to identify the

long-axis sliding motion as a ‘killer’ phonon mode, which in some molecules contributes more than

80% to the total thermal disorder. Based on this insight we are able to rationalize observed mobility

trends between different materials and derive important molecular design guidelines for new high

mobility molecular semiconductors.

[1] A. S. Eggeman, S. Illig, A. Troisi, H. Sirringhaus and P. A. Midgley, Nature Materials 12, 1045.

(2013)

[2] S. Illig, A. S. Eggeman, A. Troisi, L. Jiang, C. Warwick, M. Nikolka, G. Schweicher, S. G. Yeates, Y. H.

Geerts, J. E. Anthony and H. Sirringhaus, Nat. Commun. 7, 10736. (2016)

[3] S. Fratini, D. Mayou and S. Ciuchi, Adv. Funct. Mater. 26, 2292. (2016)

[4] S. Fratini, S. Ciuchi, D. Mayou, G. Trambly de Laissardière and A. Troisi, Nature Materials 16, 998.

(2017)

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Charge dissociation at organic heterojunctions: interface roughness versus ultrafast

delocalization.

Julien Gorenflot1, Maxime Babics1, Kai Wang1, Ru- Ze. Liang1, Zhipeng Kan1, Pierre M. Beaujuge1,

Frédéric Laquai1

1 King Abdullah University of Science and Technology, KAUST Solar Center (KSC), Physical Sciences and

Engineering Division (PSE), Material Science and Engineering Program (MSE), Thuwal, Saudi Arabia

The last years have seen tremendous progress in the understanding of charge separation at organic

electron donor/electron acceptor heterojunctions. Charge separation has been shown to be ultrafast

rather than passing through an equilibrium state,[1] while not requiring excess energy from the

bound excitons.[2] Several studies have found evidences of ultrafast charge delocalization which is a

serious candidate to explain ultrafast charge separation.[3,4] In this contribution, we present a series

of OPV systems recently studied by us using transient absorption spectroscopy. While in some

systems close packing seem to aid charge separation [5], others exhibit the most efficient separation

in films less favorable to ultrafast delocalization. [6] We rationalize our observations by recent

findings from the Andrienko group [7], showing that interface roughness has a pronounced impact

on the interfacial states’ binding energy, effectively reducing it without the need for enhanced

ultrafast delocalization.

[1] I. A. Howard, R. Mauer, M. Meister, and F. Laquai, JACS, 132, 14866. (2010)

[2] K. Vandewal, S. Albrecht, E. T. Hoke, K. R. Graham, J. Widmer, J. D. Douglas, M. Schubert, W. R.

Mateker, J. T. Bloking, G. F. Burkhard, A. Sellinger, J. M. J. Fréchet, A. Amassian, M. K. Riede, M. D.

McGehee, D. Neher, and A. Salleo, Nature Mat., 13, 63. (2014)

[3] A. A. Bakulin, A. Rao, V. G. Pavelyev, P. H. M. van Loosdrecht, M. S. Pshenichnikov, D. Niedzialek, J.

Cornil, D. Beljonne, R. H. Friend, Science, 335, 1340. (2012)

[4] S. Gélinas, A. Rao, A. Kumar, S. L. Smith, A. W. Chin, J. Clark, T. S. van der Poll, G. C. Bazan, R. H.

Friend, Science, 343, 512. (2014)

[5] J. Gorenflot, A. Paulke, F. Piersimoni, J. Wolf, Z. Kan, F. Cruciani, A. El Labban, D. Neher, P. M.

Beaujuge, and F. Laquai, Adv. Energy Mater., 8(4), 1701678. (2018)

[6] O. Alqahtani, M. Babics, J. Gorenflot, V. Savikhin, T. Ferron, A. H. Balawi, A. Paulke, Z. Kan, M.

Pope, A. J. Clulow, J. Wolf, P. L. Burn, I. R. Gentle, D. Neher, M. F. Toney, F. Laquai, P. M. Beaujuge,

and B. A. Collins, Adv. Energy Mater., 8(19), 1702941. (2018)

[7] C. Poelking, and D. Andrienko, JACS, 137(19), 6320. (2015)

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Modular sensor platform based on electrolyte-gated organic field-effect transistor from biomolecules (glucose and urea) to nitroaromatic explosive (DNT, TNT) detection

Giovanni Ligorio1, Hugo. J.N.P.D. Mello1,2, Simon Dalgleish1, Anna Grafl3, Marcelo Mulato2, Hans G. Börner3 and Emil J. W. List-Kratochvil1,4

1 Institut für Physik, Institut für Chemie & IRIS Adlershof,

Humboldt‐Universität zu Berlin, Berlin (Germany)

2 Department of Physics, Faculty of Philosophy, Sciences and Letters at Ribeirão Preto,

University of São Paulo, Ribeirão Preto (Brazil)

3 Department of Chemistry, Laboratory for Organic Synthesis of Functional Systems;

Humboldt-Universität zu Berlin, Berlin (Germany)

4 Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Berlin (Germany)

The outstanding features of organic-based devices, such as low temperatures processability, low-cost fabrication, miniaturization and integration on flexible substrates, is leading to smart, cheap and disposable technologies. Due to the good biocompatibility of the organic materials these technologies are more and more pushing towards application in the health, food and environmental monitoring. Aside from the main application of organic field-effect transistors (OFETs) in display and integrated circuit technology, OFETs have proved to be excellent candidates as transducers for many sensing applications. Regarding these sensing application, among the different families of OFET configuration, electrolyte-gate organic field-effect transistors (EGOETs) have the potential to be ideal transducer devices for the realization of modular sensor platforms for environmental monitoring and biomedical diagnostic. The sensing capabilities of EGOFETs rely on the possibility of functionalizing the gate electrode by means of specific molecules or functional groups able to absorb/detect the target molecules inside the electrolyte.

In this work, we report on a modular EGOFET based enzymatic biosensor for glucose and urea, which displays a linear response in the range between 10-6 and 10-3 mol/L. This biosensor relies on the immobilization of specific enzymes for glucose or urea on gold rods acting as gate electrodes in a poly(3-hexylthiophene) (P3HT) based EGOFET. The use of the bioreceptors proved to be selective and cross-selective in the devices. In order to further expand the generic modular approach of the sensing platform, which relays on the specific functionalization of the (parallel) gates, an explosive detection sensor has been fabricated upon immobilization of peptides acting as compound specific binding domains, which enable the physisorption of nitroaromatic explosive molecules (DNT and TNT).

s s s s s s f)J-(Jri]rS~ s s s CJ s s s f)J-(Jri]rS~ 0

II s

s s s 0,\/P s s s ~s~

(a) (b)

1 Photofunctional sulfur-bridged oligomers and polymers 2 3 Peter R. Christensen,1 Chad D. Cruz,2 Elise Caron,1 Jennifer Yuan,1 Clàudia Climent,3 David Casanova,4,5

4 Christopher J. Bardeen,2 Michael O. Wolf1

5 6 1 Department of Chemistry, University of British Columbia, Vancouver, British Columbia (Canada)

7 2 Department of Chemistry, University of California Riverside, Riverside, California (United States)

8 3 Departamento de Fisica Teorica de la Materia Condensada, Universidad Autonoma de Madrid,

9 Madrid (Spain)

10 4 Donostia International Physics Center (DIPC), Paseo Manuel de Lardiazabal 4, 20018 Donostia,

11 Euskadi (Spain)

12 5 Basque Foundation for Science, 48013 Bilbao, Euskadi (Spain)

13 14 Sulfur-based bridging groups (sulfides, sulfoxides and sulfones) provide a convenient, tunable

15 approach to varying the electronic behaviour of -functional materials. The photophysical and

16 photochemical behavior of several classes of sulfur-bridged materials will be described. Symmetric

17 chromophore dimers are of interest for applications in optoelectronic devices as they offer the

18 potential for optimization of energy and charge transfer processes. A series of sulfur-bridged

19 chromophore dimers in which the intradimer electronic coupling can be varied by changing the

20 oxidation state of the bridging sulfur group will be discussed (Figure 1a).[1,2] We show that excited

21 state charge transfer character can be varied by tuning the bridge oxidation state. Steady-state and

22 time-resolved spectroscopy, in combination with computational results are used to evaluate the

23 electronic structure of these dimers. Applications of these systems in optoelectronic devices will be

24 discussed, and polymers containing these functional groups will be described.[3] We have discovered

25 a series of sulfur-bridged anthracenes which undergo a unique photochemical extrusion of sulfur

26 monoxide (SO) to give an emissive -conjugated dianthracene product (Figure 1b).[4,5] Applications

27 of this novel photoreaction in fluorescent photopatterning and fabrication of anti-counterfeiting

28 security patches will be discussed.

29

30 Figure 1. (a) Sulfur-bridged terthiophene dimers and (b) dianthryl sulfoxide photochemistry.

31 [1] P.R. Christensen, J.K. Nagle, A. Bhatti, M.O. Wolf, J. Am. Chem. Soc. 135, 8109 (2013). 32 [2] C.D. Cruz, P.R. Christensen, E.L. Chronister, D. Casanova, M.O. Wolf, J. Am. Chem. Soc. 137, 12552 33 (2015). 34 [3] E. Caron, M.O. Wolf, Macromolecules 50, 7543 (2017). 35 [4] P.R. Christensen, B.O. Patrick, É. Caron, M.O. Wolf, Angew. Chem. Int. Ed. 52, 12946 (2013). 36 [5] P.R. Christensen, M.O. Wolf, Adv. Funct. Mater. 26, 8471 (2016).

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Morphology and transition temperatures of conjugated polymer blends for solar cells

Caroline Pan1, Anirudh Sharma1,2, David A. Lewis1 and Mats R. Andersson1

1Flinders Institute for NanoScale Science and Technology, Flinders University, Adelaide (Australia) 2Laboratoire de Chimie des Polymères Organiques, University of Bordeaux, Bordeaux (France)

Polymer solar cells have gained considerable interest during the last decades. The most promising

active layer material comprises so-called bulk-heterojunction blends of a donor polymer that is finely

mixed with an acceptor. The photovoltaic performance has increased rapidly over the last years with

high power conversion for lab-scale single-junction devices. Over the years our efforts have mainly

been focused on design and synthesis of new materials but also on morphology control and interface

materials.

The thermal stability of solar cell materials and interfaces are important prerequisites, as PSCs are

often exposed to elevated temperatures during fabrication and operation. Glass transition

temperature is a critical parameter that determines the kinetics of molecular reorganization of

polymer semiconductors during thermal treatments. In this work, we discuss a simple and general

method for measuring the Tg of conjugated polymers and polymer-molecule blends using dynamic

mechanical thermal analysis (DMTA).[1] Compared to normal DMTA measurements the materials are

deposited onto a supporting substrate. It is a very versatile method which enables measurement of

thermal transitions utilising as little as 5-10 mg of the polymer-molecule blend. The technique is a

highly sensitive method of measuring the Tg of materials, including sub-Tg transitions and melting

points.

By systematically modifying the polymer side chains and the backbone structure, the origin of Tg and

sub-Tg transitions has been successfully correlated to the polymer structures for a number of

different polymers. Thermal transitions of a range of high performing polymers applied in organic

photovoltaics, including TQ1, PTNT, PTB7, PTB7-Th and N2200 have been systematically studied in

this work. According to the measurements some of these polymers do not have an amorphous part,

changing the way how the morphology should be described for these materials. We infer that the

main phase in these polymers consists of aggregates of pi-stacked conjugated polymers chains having

a minimal amorphous content in between the aggregates. This is in contradiction to the classical

picture of polymers, consisting of amorphous and crystalline phases.

[1] A. Sharma, X. Pan, M.R. Andersson, D. Lewis, Macromolecules 50(8), 3347 (2017).

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Selective self-assembly of 2,3-diaminophenazine molecules on MoSe2 mirror twin

boundaries

Xiao Yue He1; Ming Yang2; Yu Li Huang*1; Andrew Thye Shen Wee*1

1Department of Physics, National University of Singapore, Singapore 2Institute of Materials Research & Engineering (IMRE), A*STAR (Agency for Science, Technology and

Research), Singapore

More recently, mirror twin boundaries (MTBs) in atomically thin MoSe2 films have attracted increasing attention due to the direct observation of one-dimensional (1D) charge density waves (CDW) along the MTBs at low temperatures. Such metallic line defects are usually unfavourable for carrier/energy transport and optical applications. However, they are often catalytically active due to their large density of states (DOS). Using a combination of ultrahigh vacuum scanning tunnelling microscopy /spectroscopy (STM/STS) and non-contact atomic force microscopy (nc-AFM) techniques, we reveal such well-defined line defects may potentially be used as templates for self-assembly of molecules. 2,3-diaminophenazine (DAP), an amino derivative of phenazine with promising luminescence, electrochemical and biochemical applications, is selected for investigating the template effect of the dense MTB network. We observed the formation of a regular porous network of DAP molecules that map onto the wagon-wheel patterns of the underlying MoSe2. First-principles calculations further suggest that the active amino groups in the DAP molecules play a critical role in this preferential adsorption behavior, as charge redistribution occurs mainly close to the amino groups. By comparing the adsorption energies of different adsorption configurations, the configuration with the DAP molecule adsorbed parallel to and on the top of the MTBs is found to be the most stable, in agreement with the experimental results. This pioneering study demonstrates that organic molecule self-assembly can be facilitated by domain boundaries in epitaxial 2D TMDs.

This is the last line of your abstract.

Development of Layered-Crystalline BBBT-based Organic Semiconductor Materials with

Long Alkyl Chain

Toshiki Higashino1, Shunto Arai2, Tatsuo Hasegawa2

1Electronics and Photonics Research Institute, National Institute of Advanced Industrial Science and

Technology (AIST), Tsukuba (Japan) 2Department of Applied Physics, The University of Tokyo, Tokyo (Japan)

In solution-processable organic semiconductors, the π-conjugated skeleton is generally modified by an alkyl chain in order to increase solvent solubility. Recently, it is shown that some kinds of long alkyl-chain substitutions are quite effective to increase (or enhance) the layered crystallinity, the feature of which is critical for obtaining high performance organic thin-film transistors (OTFTs), as is demonstrated for a series of benzothieno[3,2-b]benzothiophene (BTBT)-based organic semiconductors [1]. Here we report syntheses of symmetrically/asymmetrically-alkylated benzo[1,2-b:4,5-b']bis[b]benzothiophene (BBBT) derivatives (diC10-BBBT and Ph-

R1=R2=decyl: diC10-BBBTR1=Ph, R2=decyl: Ph-BBBT-C10

R1=R2=alkyl: dialkyl-BTBTR1=Ph, R2=alkyl: Ph-BTBT-Cn

BBBT-C10). The BBBT is a compound of five-ring-fused thienoacene family, regarded as an extended system of the BTBT. We investigated the effects of π-extension and long alkyl-chain substitution on the molecular packing, thermal stability, and OTFT properties. Both of the symmetric diC10-BBBT and the asymmetric Ph-BBBT-C10 were synthesized according to a modified literature procedure [2]. The diC10-BBBT forms a lamellar herringbone packing structure, in contrast to the π-stacking structure with a longitudinal molecular slip as seen in dibutyl-BBBT with short alkyl-chain substitutions [2]. The asymmetric Ph-BBBT-C10 forms a bilayer-type herringbone structure, similar to those of Ph-BTBT-Cn [1]. Note that such herringbone packing is optimal for the production of high performance OTFTs. We show that the long alkyl-chain substitution is effective to obtain the herringbone packing, and discuss the structure-property relationship in these materials.

[1] a) S. Inoue, H. Minemawari, J. Tsutsumi, M. Chikamatsu, T. Yamada, S. Horiuchi, M. Tanaka, R. Kumai, M. Yoneya, T. Hasegawa, Chem. Mater. 27, 3809 (2015); b) H. Minemawari, M. Tanaka, S. Tsuzuki, S. Inoue, T. Yamada, R. Kumai, Y. Shimoi, T. Hasegawa, Chem. Mater. 29, 1245 (2017). [2] P. Gao, D. Beckmann, H. N. Tsao, X. Feng, V. Enkelmann, W. Pisula, K. Müllen, Chem. Commun. 1548 (2008).

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- 10 ')I E u <( 5 -S >,

:!= (/)

0 C: Q)

"Cl ..... C: Q) -5 ..... ..... :::J 0

-10

-15 0.0 0.2 0.4 0.6 0.8

Applied voltage (V)

Microscopy Imaging and 3D-tomography of organic solar cell bulk heterojunction

Artem Levitsky1, Xiaolei Chu2, Adam Moule2, Gitti L. Frey1

1Department of Material Science and Engineering, Technion Israel Institute of Technology, Haifa (Israel)

2Department of Chemical Engineering, University of California Davis, CA (USA)

The understanding of processing-structure-properties relationship in organic solar cells is severely limited by lack of experimental tools suitable for characterizing the bulk heterojunction morphology. More specifically, techniques that rely on order are impractical for the disordered domains abundant in the film; surface analysis techniques do not necessarily represent the underlying bulk structure, and the all-organic composition imposes inherent low z-contrast hindering imaging by electron microscopy. Recently, we suggested the use of vapor phase infiltration (VPI) to characterize the internal morphology of BHJs. VPI infuses inorganic materials into an organic matrix by exposure to gaseous precursors that diffuse into the film and in-situ convert to an inorganic product. The diffusion process proceeds selectively through domains with high free-volume leading to inorganic deposition selectively along the diffusion paths. The diffusion network is easily visualized using electron microscopy because of the high contrast between the organic matrix and the accumulated inorganic phase. This labelling approach is in concept similar to the staining approach used to image low contrast biological specimens in electron microscopy. Furthermore, the inorganic phase deposited in the organic film also provides material stability for HRTEM imaging and tomography.

We used the VPI methodology to characterize the morphologies polymer:fullerene and polymer:non-fullerene BHJs as a function of composition, thermal treatments and processing technique. We were able to visualize crucial characteristics of BHJ morphologies, such as domains size, shape and distribution, 3D-connectivity and interface area through fast and straightforward HRSEM and more advanced HRTEM imaging and tomography. For example, The HRSEM image of a 1:1.2 polymer:fullerene BHJ (bottom) shows the distribution and size of polymer domains (bright contrast) and fullerene domains (dark contrast) in a film cross section. The 3D tomography reconstruction (top) shows the interconnectivity of the polymer (yellow) and fullerene (red) networks through the film. The spatial mapping of the phase morphology and the phase behavior of each system were then correlated with device performances, as shown in the Figure, to provide insight on the processing-structure-property relationship towards directing improved devices.

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Organic semiconductor film transfer for 3D/2D hybrid devices -mandatory blank line-

1Bert Nickel, 1Batuhan Kalkan, 2Anthony George, 2Andrey Turchanin -mandatory blank line-

1 Fakultät für Physik und CENS, Ludwig-Maximilians-Universität, München (Germany) 2 Institut für physikalische Chemie, Friedrich Schiller Universität ,Jena (Germany)

-mandatory blank line-We developed a method to stabilize and transfer organic semiconductor nanofilms. The method is based on crosslinking of the topmost layers of organic films by low energy electron irradiation. The irradiated films, which are deposited on a dissoluble interlayer, are detached from their original substrates and subsequently deposited onto a new substrate. This allows for the fabrication of highly ordered interfaces of organic 3D films and 2D materials. We demonstrate the versatility of this approach by the fabrication of ambipolar MoS2-pentacene field effect transistors. First we study transport properties in order to confirm ambipolar behaviour. Second we apply raster scanning techniques such as photocurrent microscopy and photoluminescence spectroscopy in order to study the local characteristics of such devices with submicron resolution. This technique allowed us previously to identify in unipolar devices injection barriers at contacts and trapping effects in the channel. In ambipolar devices, we can probe also for the generation of free carriers by exciton splitting and charge separation at the 2D/3D heterojunction. Our initial experiments focus on pentacene and MoS2 as 3D and 2D material, however, the film transfer method should also be applicable also to C60, which would open a wide range of possible hybrid p/n junctions and related devices.

PBFBT-NP

NTR ~ PBFBT-NP

Normal A549 cell Anaerobic A549 cell

1 Functional Conjugated Polymers-Based Biosensors and Bioanalysis 2

1 1 1 1 13 Qi, Zhao , Ziqi Zhang , Zhuanning Lu , Yantao Zhao , Yanli Tang 4 5 1 School of Chemistry and Chemical Engineering, Shaanxi Normal University,

6 Xi'an, P. R. China 710119

7 8 Conjugated polymers (CPs) have attracted much attention because of their good light-harvesting 9 ability and strong fluorescence yield, which exhibits the broad applications in biological sensing, cell

10 imaging, photodynamic therapy, etc. [1] Recently, we have devoted ourselves to the design and 11 synthesis of functional conjugated polymers and their applications in biosensors and bioanalysis. A 12 series of new water-soluble conjugated polymers modified with functional groups to specifically 13 recognize targets have been synthesized. Correspondingly, several new biosensors with high 14 selectivity and ultra-rapidity have been constructed based on these conjugated polymers. [2-4] For 15 example, a) PBFBT-NP probe contains a nitro group which presents specific recognition with 16 nitroreductase and are used in hypoxia, cell imaging and antibacterial applications; b) a novel CPs-17 based combination probe specifically detects ATP based on multisite-binding and the FRET 18 mechanism; c) a new water-soluble conjugated polymer (PBFB-PDA-NMe3

+) with o-diaminophenyl 19 group is synthesized as a fluorescence probe for ultra-rapid and highly selective detection of 20 endogenous nitric oxide. In addition, in virtue of high reactive oxygen species produced by 21 conjugated polymers, several methods have been established for highly efficient antipathogen under 22 irradiation with UV, Visible or NIR light. [5-7] The structure-activity relationship was also investigated 23 for future applications in antipathgen and antitumor based on conjugated polymers.

24 25 Figure 1 . Schematic Presentation of detection of NTR and Cell Hypoxia Diagnosis

26 References: 27 [1] C. Zhu, L. Liu, Q. Yang, F. Lv, S. Wang, Chem. Rev. 112, 4687. (2012) 28 [2] X. Zhang, Q. Zhao, Y. Li, X. Duan, Y. Tang, Anal. Chem. 89, 5503. (2017) 29 [3] Q. Zhao, Z. Zhang, Y. Tang, Chem. Commun. 53, 9414. (2017) 30 [4] Q. Zhao, H. Zhao, Y. Guo, Z. Zhang, Y. Hu, Y. Tang, Anal. Chem. 90, 12663. (2018) 31 [5] Q. Zhao, J. Li, X. Zhang, Z. Li, Y. Tang, ACS Appl. Mater. Interfaces 8, 1019. (2016) 32 [6] J. Li, Q. Zhao, F. Shi, C. Liu, Y. Tang, Adv. Healthc. Mater. 5, 2967. (2016) 33 [7] L. Zhai, Z. Zhang, Y. Zhao, Y. Tang, Macromolecules 51, 7239. (2018) 34 35 36 37 38 39 40 41

(a) ~~~h••;~ ..... :::-.:."•-S1 relaxed ....;=""---- Free

Carriers

hv Intermolecular Charge _______ -

Transfer : Strong Acceptor

(b) ! -Weak Acceptor

Investigating Acceptor Gradient Polymer Donors for Non-fullerene Organic Solar Cells

Austin L. Jones1, Zilong Zheng1, Parand Riley2, Ian Pelse1, Junxiang Zhang1, Seth R. Marder1, Franky So2, Jean-Luc Brédas1, John R. Reynolds1

1School of Chemistry and Biochemistry, Center for Organic Photonics and Electronics, Georgia

Institute of Technology, Atlanta (USA), 2 Department of Materials Science and Engineering, North

Carolina State University, Raleigh (USA)

Organic Solar Cells (OSCs) have exhibited very impressive advances in the last decade with power conversion efficiencies (PCE) improving from 7% to 14% in single junction cells. One of the leading reasons for this significant improvement is the emergence of non-fullerene acceptors (NFA) which possess strong absorption in the visible and near-IR regions and are easily synthetically manipulated, as compared to fullerene acceptors. Further, the Voc (> 1 V) in many non-fullerene cells have improved significantly due to the increased electron affinity in some NFAs alongside the simultaneous increase in ionization potential in many polymer donors. Recently, there have been a number of small driving force polymer/NFA cells designed that exhibit high Voc and high current resulting in excellent PCEs. Although these systems have shown promise, they still lag behind state of the art cells due to diminished Jsc owing to longer lived intermolecular charge transfer states which can have detrimental charge recombination processes. In this work, polymer donors were designed with an acceptor gradient motif that incorporate a strong acceptor unit flanked by weaker acceptor units followed by a donor with the expectation of less charge recombination in low driving force systems. The gradient effect in the polymer backbone may provide greater charge separation (less recombination) via an intramolecular charge transfer state (S1 relaxed) as compared to traditional donor-acceptor polymers (Figure 1).

Figure 1: (a) Jablonski diagram showing the intramolecular charge transfer mechanism. (b)

Acceptor gradient polymer example (T2-BTDF-(TE2))

Density functional theory (DFT) calculations were performed to characterize the intramolecular charge-transfer state and revealed greater charge-transfer character in the S1 relaxed state versus the S1

vertical state. Small driving force solar cells were fabricated using both a gradient polymer (Figure 1) and a non-gradient isomeric polymer blended with IDTBR and ITIC. These cells produced poor performances due to reduced hole transport because of the large ionization potentials of the polymer donors. Therefore, an NFA (ITIC-4F) with a larger ionization potential was utilized to produce cells with PCEs of 3.6% for the gradient polymer and 7.3% with the non-gradient polymer. This study exemplifies the importance of driving force for both electron and hole transfer in NFA solar cells.

Insights into p-doping of P3HT by Electron Paramagnetic Resonance

Claudia E. Tait1, Malavika Arvind2, Berthold Wegner3,4, Norbert Koch3,4, Dieter Neher2, Jan Behrends1

1 Department of Physics, Freie Universität Berlin, Berlin (Germany) 2 Soft Matter Physics, Universität Potsdam, Potsdam-Golm (Germany)

3 Helmholtz-Zentrum Berlin für Materialien und Energie, Berlin (Germany) 4 Institut für Physik & IRIS Adlershof, Humboldt-Universität zu Berlin, Berlin (Germany)

The achievement of efficient and controlled molecular doping of organic semiconductors promises to significantly advance the field of organic electronic devices. However, an in-depth understanding of the doping process is required to guide the design of improved semiconductor materials and molecular dopants [1,2]. Electron Paramagnetic Resonance (EPR) Spectroscopy is a technique uniquely suited to investigate the nature and dynamics of the paramagnetic species generated by introduction of dopant molecules into solutions or films of organic semiconductors [3,4].

In this study, a multi-frequency continuous-wave and pulse EPR approach was used to investigate p-type doping of P3HT with a series of different molecular dopants, including F4TCNQ and tris-(pentafluorophenyl)borane (BCF). Continuous-wave EPR was used to quantify the concentration of paramagnetic species as a function of dopant concentration and revealed significant differences in the spectral signatures depending on the dopant molecule and the doping concentration. Measurements at different microwave frequencies provided further insights into the nature of the detected paramagnetic species and allowed the separation of signals arising from the polaron on P3HT and the paramagnetic state of the dopant. Since EPR is only sensitive to species with unpaired electrons, tightly-bound charge transfer states or bipolarons cannot directly be detected. However, the presence of charge-transfer states can in some cases be inferred from comparison of EPR and UV-Vis absorption data, and the presence of bipolarons at high dopant concentrations from a decrease in the number of spins. Pulse EPR measurements performed at low temperatures additionally allow a more detailed investigation of the dynamics of the P3HT polaron through measurements of the spin-lattice and spin-spin relaxation times. EPR techniques aimed at determining the hyperfine coupling between the unpaired electrons and magnetic nuclei in their surroundings aid in the assignment of different EPR spectra to polymer or dopant species and in the characterisation of the generated polaron. Here, the extent of delocalisation of the P3HT polaron was determined using the ENDOR (Electron Nuclear DOuble Resonance) technique to measure the hyperfine couplings between the hole and the protons on the polymer chain. A comparison of F4TCNQ-doped regioregular and regiorandom P3HT shows clearly reduced hole delocalisation in regiorandom P3HT, which, combined with a significantly reduced spin concentration, supports the hypothesis that increased hole delocalisation improves doping efficiency by promoting the separation of charge-transfer states [5].

[1] I. Salzmann, G. Heimel, M. Oehzelt, S. Winkler, N. Koch, Acc. Chem. Res. 49, 370-378 (2016). [2] I.E. Jacobs, A.J. Moulé, Adv. Mater. 29, 1703063-1-39 (2017). [3] A. Aguirre, P. Gast, S. Orlinskii, I. Akimoto, E.J.J. Groenen, H. El Mkami, E. Goovaerts, S. Van

Doorslaer, Phys. Chem. Chem. Phys. 10, 7129-7138 (2008). [4] R. Steyrleuthner, Y. Zhang, L. Zhang, F. Kraffert, B. P. Cherniawiski, R. Bittl, A.L. Briseno, J.-L. Brédas,

J. Behrends, Phys. Chem. Chem. Phys. 19, 3627-3639 (2017). [5] J. Gao, E.T. Niles, J.K. Grey, J. Phys. Chem. Lett. 4, 2953-2957 (2013).

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Interfacial Film Morphology in Ultrathin Organic Field-Effect Transistors

Wojciech Pisula1,2

1Department of Molecular Physics, Lodz University of Technology, Lodz (Poland) 2Max Planck Institute for Polymer Research, Mainz (Germany)

The first few semiconducting layers next to the dielectric interface are of vital importance, because

they dominate the charge carrier transport of the device. At certain conditions it is possible to

solution process organic semiconductor films in a monolayer precision. This allows to vary the film

thickness from submonolayer to mulitlayers to systematically study the microstructure formation

and charge carrier transport at the semiconductor/dielectric of the organic semiconductor in a field-

effect transistor. In this context, it has been proven that the first monolayer has also essential

importance for the microstructure evolution of the bulk film. This microstructure in turn is necessary

for creating the required percolation pathways for the charge carriers in transistors. A further

important aspect is the structural inhomogeneity of the semiconducting films. This is presentation it

will be reported that the interfacial microstructure of organic semiconductors near the dielectric has

a minor impact on the charge carrier transport [1]. The concluded transport mechanism is based on a

by-passing of the interfacial smaller domains by the charge carriers through ordered larger domains

within the multilayers. Interestingly, these findings are valid for a broad range of organic

semiconductors which are crystalline or semi-crystalline, and for films deposited from solution or

sublimated.

This work was supported by the National Science Centre, Poland, through the grant UMO-

2015/18/E/ST3/00322. We acknowledge the BL09 beamline at DELTA synchrotron in Dortmund for

the support in the GIWAXS measurements.

[1] a) M. Li, C. An, T. Marszalek, I. Lieberwirth, M. Baumgarten, K. Müllen, W. Pisula, Adv. Mater. 28,

2245 (2016); b) M. Li, F. Hinkel, K. Müllen, W. Pisula, Nanoscale 8, 9211 (2016); c) M. Li, T. Marszalek,

Y. Zheng, I. Lieberwirth, K. Müllen, W. Pisula, ACS Nano 10, 4268 (2016); d) M. M. Li, C. B. An, T.

Marszalek, M. Baumgarten, H. Yan, K. Müllen, W. Pisula, Adv. Mater. 28, 9430 (2016); e) M. M. Li, T.

Marszalek, K. Müllen, W. Pisula, ACS Appl. Mater. Interfaces 8, 16200 (2016); f) L. Janasz, D. Chlebosz,

M. Gradzka, W. Zajaczkowski, T. Marszalek, K. Müllen, J. Ulanski, A. Kiersnowski, W. Pisula, J. Mater.

Chem. C 4, 11488 (2016); g) L. Janasz, A. Luczak, T. Marszalek, B. G. R. Dupont, J. Jung, J. Ulanski, W.

Pisula, ACS Appl. Mater. Interfaces 9, 20696 (2017); h) L. Janasz, M. Gradzka, D. Chlebosz, W.

Zajaczkowski, T. Marszalek, A. Kiersnowski, J. Ulanski, W. Pisula, Langmuir 33, 4189 (2017); i) L.

Janasz, T. Marszalek, W. Zajaczkowski, M. Borkowski, W. Goldeman, A. Kiersnowski, D. Chlebosz, J.

Rogowski, P. Blom, J. Ulanski, W. Pisula, J. Mater. Chem. C 6, 7830 (2018); j) M. Li, D. K. Mangalore, J.

Zhao, J. H. Carpenter, H. Yan, H. Ade, H. Yan, K. Müllen, P. W. M. Blom, W. Pisula, D. M. de Leeuw, K.

Asadi, Nat. Commun. 9, 451, (2018).

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Electronic transport through organic spin-containing molecules and their use for manipulating electronic properties of surfaces

Andrés Gómez,1¶ Valentin Diez-Cabanes,2¶ Manuel Souto,1 Nerea Gonzalez-Pato,1 Carmen Ocal,1

Jerome Cornil,2 Imma Ratera, 1 Jaume Veciana.1

1Institut de Ciència de Materials de Barcelona (ICMAB-CSIC)/CIBER-BBN, Campus de Bellaterra, E-

08193 Cerdanyola del Vallès, Spain 2University of Mons—UMONS Place du Parc 20, 7000 Mons, Belgium.

Organic free radicals are neutral molecules exhibiting magnetic and optical properties due to the presence of an unpaired electron. This property together with their low spin-orbit couplings and weak hyperfine interactions make them good candidates for molecular spintronics insofar the radical character is preserved in solid state and the molecules are properly arranged on a solid state device. To exploit such properties we used functionalized polychlorinated triphenylmethyl (PTM) radicals to attach them as self-assembled monolayers (SAMs) on metallic surfaces, like Au, Ag, Cu, or graphene, exploring the transport properties through such spin-containing organic hybrid systems. [1] Also the transport through a single radical PTM molecules with two- (mechanically-controlled break junction) and three-terminal (electromigrated break junction) solid-state devices were reported [2]. The magnetic property of radicals in these hybrid systems is manifested by the appearance of Kondo anomalies in the transport measurements. Also molecular junctions showing rectification properties were recently reported. [3] In all cases the conductance through the radical molecules is enhanced two orders of magnitude with respect the corresponding non-radical ones which can be explained by a mediated electron transport through the SUMO orbitals in the open-shell systems. [4-5] These results paved the way towards the use of all-organic neutral radical molecules in electronic devices and spintronics. In this contribution we will present novel results obtained with SAMs based on PTM radicals bonded to ferrocene donor units for manipulating the electronic properties of metallic surfaces, like their work functions. A remarkable result showing that it is possible to switch the work function using an external input like NIR light will be presented. [6-7]

References [1] L. Yuan, C. Franco, N. Crivillers, M. Mas-Torrent, L. Cao, C. S. Suchand Sangeeth, C. Rovira, J. Veciana, C. A. Nijhuis, Nature Comm., 7, 12066 (2016). [2] R. Frisenda, R. Gaudenzi, C. Franco, M. Mas-Torrent, C. Rovira, J. Veciana, S.T. Bromley, E. Burzuri, H.S.J. van der Zant, Nano Lett, 15, 3109 (2015) [3] R. Gaudenzi, E. Burzurí, D. Reta, I. de P. R. Moreira, S. T. Bromley, C. Rovira, J. Veciana, H. S. J. van der Zant, Nano Lett. 16, 2066 (2016) [4] M. Souto, L. Yuan, D. C. Morales, L. Jiang, I. Ratera, C. A. Nijhuis, J. Veciana. J. Am. Chem. Soc., 139, 4262, (2017) [5] F. Bejarano I.J. Olavarria-Contreras, A. Droghetti, I. Rungger, A. Rudnev, D. Gutiérrez, M. Mas-Torrent, J. Veciana, H.S. J. van der Zant, C. Rovira, E. Burzurı, N. Crivillers, J. Am. Chem. Soc. 140, 1691 (2018) [6] V. Diez-Cabanes, D.C. Morales, M. Souto, M. Paradinas, F. Delchiaro, A. Painelli, C. Ocal, D. Cornil, J. Cornil, J. Veciana, I. Ratera, Adv. Mater. Technol. 2018, 1800152 (2018). [7] V. Diez-Cabanes, A. Gómez, M. Souto, N. González-Pato, J. Cornil, J. Veciana, I. Ratera, submitted

(2019)

¶ Equally contributed to the work

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Howdoes photo-oxidation of materials affect solar cellperformance?

Dargie Deribew, Vanja Blazinic, Axel Hedengren, Leif Ericsson, Ellen Moons

Department of Engineering and Physics, Karlstad University,Karlstad (Sweden)

Commercially viable solution-processed solar modules require materials with a good thermal, chemical and photochemical stability. For pi-conjugated molecules, such as those used in the active layers of organic solar cells, the simultaneous exposure to light and in-diffusing oxygen or air is particularly challenging. In this study we intentionally expose layers of solar cell materials to simulated sunlight in air in order to study the effect of photo-oxidation on the properties of the molecular semiconductor materials in the photoactive layer, as well as the hole transport materials (HTM) used as interface layers. Significant differences in photostability are found between the electron acceptors PC60BM, PC70BM and N2200, as seen from the rate of formation of photo-oxidation products by IR spectroscopy and the decrease of pi-conjugation by NEXAFS spectroscopy upon light exposure in air. Additionally, this photostability is affected when the acceptor is blended with a polymer donor. To understand how materials degradation affects solar cell performance, those photo-oxidized active layers (AL) were then incorporated in polymer solar cells with the conventional device structure ITO/HTM/AL/LiF/Al devices, using PEDOT:PSS and MoO3 as HTM. The I-V characteristics and external quantum efficiency (EQE) showed strong losses of photocurrent, fill factorand open-circuit voltage, which points towards a combination of causes. Photobleaching of the active layer contributes to the decrease in performance, however the dominant factor appears to be the inefficient charge transport through the degraded acceptor molecules and trap formation.

Charge transport layers, and in particular layers of HTMs at the interface between ITO and the active layer, have also a significant effect on the performance and stability of polymer solar cells. The commonly used PEDOT:PSS is known as a significant cause of degradation. We have studied the photostability in air of PEDOT:PSS and a number alternative HTMs, such as, thermally evaporated Molybdenum oxide (MoO3), and solution-processed Copper thiocyanate (CuSCN) and phosphomolybdic acid (PMA). All of these HTMs have high transparency and provide solar cells, with the polymer:fullerene blend TQ1:PC70BM (1:3) as active layer, with good performance. Work function measurements on the HTMs by Kelvin probe before and after exposure to light in air, revealed differences in the photostability of the surface electrical properties of these HTMs. By studying the photo-oxidation of the active layer components and the hole transport layers separately we aim at getting a better complete understanding of the critical components and processes that determine the device stability.

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Optically tunable FETs with semiconducting conjugated polymers entailing azobenzene

groups in the side chains

Deqing Zhang, Zitong Liu, Jianwu Tian, Yizhou Yang

Organic Solids Laboratory, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China.

E-mail: dqzhang@iccas.ac.cn

A number of organic and polymeric semiconductors with high charge mobilities have been developed

for improving the performances of field-effect transistors (FETs). Meanwhile, FETs whose electrical

characteristics can be tuned by external fields other than electrical voltages have received increasing

attentions. In this regard, semiconducting conjugated polymers with photo-switching behavior are

highly demanding for field-effect transistors (FETs) with tunable electronic properties.

We and other groups have demonstrated that semiconducting performance of these conjugated

molecules and polymers can be largely improved by varying the side chains. In fact, side-chain

engineering becomes a new strategy for development of high performance of organic/polymeric

semiconductors. In this presentation, we report a new design strategy for photoresponsive

semiconducting conjugated polymers by incorporating the photochromic units such as azobenzene

into the side chains. We show that azobenzene groups in the side chains of the DPP

(diketopyrrolopyrrole)-quaterthiophene conjugated polymer (PDAZO) can undergo trans-/cis-

photoisomerization in a fully reversible and fast manner. Optically switchable field-effect transistors

(FETs) were successfully fabricated with thin films of PDAZO. The drain-source currents of FETs were

reduced by 80% after UV light irradiation, and the device currents were easily restored after further

visible light irradiation. Moreover, such current photomodulation can be implemented for several

light irradiation cycles with good photo-fatigue resistance. Additionally, thin film charge mobility of

PDAZO can be reversibly modulated by alternating UV and visible light irradiations. On the basis of

theoretical calculations and GIWAXS data, we hypothesize that the dipole moment and configuration

changes associated with the trans-/cis- photoisomerization of azobenzene groups in PDAZO can

affect the respective intra-chain and inter-chain charge transporting, which is responsible for the

optically switchable behavior for FETs with thin films of PDAZO.

References

[1] Z. Liu, G. Zhang, D. Zhang, Acc. Chem. Res. 51, 1422 (2018).

[2] Z. J. Wang, Z. Liu, L. Ning, M. F. Xiao, Y. P. Yi, Z. X. Cai, A. Sadhanala, G. X. Zhang, W. Chen, H.

Sirringhaus, Chem. Mater. 30, 3090 (2018).

[3] H. Luo, C. Yu, Z. Liu, G. Zhang, H. Geng, Y. Yi, K. Broch, Y. Hu, A. Sadhanala, L. Jiang, P. Qi, Z. Cai, H.

Sirringhaus, D. Zhang, Sci. Adv. 2 (5), e1600076 (2016).

[4] J. Yao, C. Yu, Z. Liu, H. Luo, Y. Yang, G. Zhang, D. Zhang, J. Am. Chem. Soc. 138 (1), 173 (2016).

[5] Y. Yang, G. Zhang, H. Luo, J. Yao, Z. Liu, D. Zhang, ACS Appl. Mater. Interfaces 8 (6), 3635 (2016).

[6] S. Yang, Z. Liu, Z. Cai, M. J. Dyson, N. Stingelin, W. Chen, H. Ju, G. Zhang, D. Zhang, Adv. Sci. 1700048

(2017).

 

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Multipurpose Molecular Spintronic Device

Xiangnan Sun1

1National Center for Nanoscience and Technology, Beijin, (P. R. China)

Organic semiconductors, characterized by weak spin-scattering mechanisms, are attractive materials

for those spintronic applications in which the spin information needs to be retained for long times.

Prototypical spin-valve devices employing organic interlayers sandwiched between ferromagnetic

materials possess a figure of merit (measured in terms of magnetoresistance; MR) comparable to

their fully inorganic counterparts. However, many results from literature are a matter of debate as

the conductivity of the devices does not show the expected temperature dependence. Here we show

spin valves with an interlayer of bathocuproine in which the transport takes place unambiguously

through the organic layer and where the electron spin coherence is maintained over large distances

(>60 nm) at room temperature. [1] For further exploiting the multipurpose application of organic spin

devices, fluorinated copper phthalocyanine (F16CuPc) has been employed as an interlayer in spin

valve. By following an unconventional low-temperature fabrication procedure, F16CuPc-based spin

valves exhibit carrier transport that unambiguously takes place through the organic layer even at low

bias range, while the spin coherence is maintained over record-long distances (> 180 nm) at room

temperature. Additionally, we merge the spin transport with photo-response in a single device,

building a promising platform for the realization of multifunctional cells. [2] Recently, photovoltaic

molecular spintronic device has also been studied, in which light could effectively control the spin

signals. [3] To conclude, along with the development of molecular spintronics, it is clear that the

study of multipurpose spintronic devices has gradually grown into a new research and development

direction. [4]

1. Xiangnan Sun, Marco Gobbi, Amilcar Bedoya-Pinto, Oihana Txoperena, Federico Golmar, Roger

Llopis, Andrey Chuvilin, Fèlix Casanova, Luis E Hueso. Room-temperature air-stable spin transport in

bathocuproine-based spin valves, Nat. Commun. 4, 2794 (2013).

2. Xiangnan Sun, Amilcar Bedoya-Pinto, Zupan Mao, Marco Gobbi, Wenjing Yan, Yunlong Guo, Ainhoa

Atxabal, Roger Llopis, Gui Yu, Yunqi Liu, Andrey Chuvilin, Felix Casanova, Luis E. Hueso. Active

morphology control for concomitant long distance spin transport and photoresponse in a single

organic device, Adv. Mater. 28, 2609 (2016).

3. Xiangnan Sun, Saül Vélez, Ainhoa Atxabal, Amilcar Bedoya-Pinto, Subir Parui, Xiangwei Zhu, Roger

Llopis, Fèlix Casanova, and Luis E. Hueso, A molecular spin-photovoltaic device, Science 357 ,677

(2017).

4. Lidan Guo, Xianrong Gu, Xiangwei Zhu, Xiangnan Sun*, Adv. Mater. Accepted.

g2.s ., E ! :J

0.1

Plasmonically Enhanced

Photostability

i' ~lass ; Au ~

O Illumination Time(m in ) 55

2.5 iii -=-., E i :J

0.1

1 Enhanced Photo-stability of Organic Molecules Through Plasmonic Effects

2

3 Sikandar Abbas1 and Linda A. Peteanu1

4

5 1Department of Chemistry, Carnegie Mellon University, Pittsburgh, PA (USA) 6

7

8 Organic semiconductors are promising for the development of many applications including in solid

9 state lighting, flexible displays and organic-based lasing. However, a critical factor limiting their utility

10 is their inherently low stability relative to inorganic materials. This instability causes organic

11 molecules to be susceptible to oxygen damage in an irreversible process known as photo-bleaching.

12 Generally speaking, this effect not only limits device lifetimes but is also exceedingly problematic in

13 fluorescence-based imaging and in biological assays that rely on sensitive fluorescence detection.

14 Progress has been made to suppress the photo-bleaching by modifying the chemical structures of

15 fluorophores to make them resistant to degradation or by developing oxygen scavenger systems.

16 However, the increasing demand for enhanced stability of single molecules requires new strategies

17 beyond these chemical approaches. Plasmonic engineering offers one avenue to alter the decay rates

18 of fluorophores and modify the emission from single molecules. Here, we demonstrate that by

19 carefully engineering the properties of ultra-thin gold films to match the plasmon with the emission

20 of organic molecules a photostability enhancement of more than 60-fold can be achieved. As an

21 example, we successfully demonstrated that OPPV-13, an oligomer of poly [2-methoxy-5(2'-

22 ethylhexyloxy)-1,4-phenylene]vinylene, deposited on 2 nm thick Au substrates retains its

23 fluorescence under constant illumination in ambient conditions for 45 minutes compared to less than

24 2 minutes when it is deposited on glass substrates. The underlying mechanism of this remarkable

25 enhanced photostability is probed using a variety of microscopy-based tools and extensions to other

26 opto-electronic materials are described. This enhanced stability observed for both single molecules

27 and thin films will be useful in many of the applications described above.

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Construction of Organic Thin-film Transistors for Multiple Sensing Applications

Chong-an Di I Fengjiao Zhang

Laboratory of Organic Solids, Institute of Chemistry, Chinese Academy of Sciences, Beijing, 100190 P.

R. China

E-mail: dicha@iccas.ac.cn

Organic devices are promising candidates for next-generation smart products owing to their

intrinsically light-weight, prominent flexibility, and potential for low-cost.[1-3] Benefiting from

systematic studies on functional materials and device engineering, we proposed several strategies to

fabricate sensing devices based organic thin-film transistors (OTFTs).[4-9] For instance, we fabricated

flexible suspended gate OTFTs (SGOTFTs) using a simple lamination method.[6] By combining organic

thin-film transistors with a suspended-gate device geometry, the SGOTFT provide an effective way

for ultra-sensitive pressure detection. The fabricated devices displayed an unprecedented sensitivity

of 192 kPa-1

and a low limit-of-detection pressure of 0.5 Pa by fine-tuning the material properties of

the suspended gate. Furthermore, several sensing device based on SGOTFTs have been

demonstrated and exhibit their applications in health monitoring and artificial intelligence.[7-8] More

recently, by tailoring the neighboring-conductive-channel organic layer using a plasma-assisted-

interfacial-grafting method, we introduced a molecular antenna on the surface of organic transistors

to enable direct interaction between the semiconductors in the conductive channel and the target

biological analytes in solution.[9] These results demonstrate promising applications of OFETs in

flexible sensing elements.

1. C. A. Di, F. J. Zhang, D. B. Zhu, Adv. Mater. 25, 313 (2013).

2. Y. P. Zang, D. Z. Huang, C. A. Di, D. B. Zhu, Adv. Mater. 28, 4549 (2016).

3. Y. P. Zang, F. J. Zhang, C. A. Di, D. B. Zhu, Mater. Horiz. 2, 140 (2015).

4. F. J. Zhang, C. A. Di, N. Berdunov, Y. Y. Hu, Y. B. Hu, X. K. Gao, Q. Meng, H. Sirringhaus, D. B. Zhu,

Adv. Mater. 25, 1401(2013).

5. Y. P. Zang, F. J. Zhang, D. Z. Huang, C. A. Di, Q. Meng, X. K. Gao, D. B. Zhu, Adv. Mater. 26, 2862

(2014).

6. Y. P. Zang, F. J. Zhang, D. Z. Huang, X. K. Gao, C. A. Di, D. B. Zhu, Nat. Commun. 6, 6269 (2015).

7. Y. P. Zang, F. J. Zhang, D. Z. Huang, C. A. Di, D. B. Zhu, Adv. Mater. 27, 7979 (2015).

8. Y. P. Zang, H. G. Shen, D. Z. Huang, C. A. Di, D. B. Zhu, Adv. Mater. 29, 1606088 (2017).

9. H. G. Shen, Y. Zou, Y. P. Zang, D. Z. Huang, W. L. Jin, C. C. A Di, D. B. Zhu, Mater. Horiz. 5, 240,

(2018).

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Quantum Interference Effects in Charge Transfer and Single Molecule Conductance

-mandatory blank line-

Ferdinand C. Grozema,1 Nicolas Renaud,1 Natalie Gorczak,1 Riccardo Frisenda2 and Herre S.J. van der

Zant.2

-mandatory blank line-1 Department of Chemical Engineering, Delft University of Technology, Delft (The Netherlands)

2 Kavli Institute of Quantum Nanoscience, Delft University of Technology, Delft (The Netherlands)

-mandatory blank line-

In the context of the continuously decreasing sizes of the individual active elements in integrated

circuits it is of considerable fundamental and practical interest to study the smallest imaginable

devices, those consisting of single molecules. In most current designs of single molecule devices,

quantum mechanical effects that are operative on the molecular scale, such as wave function

interference, are disregarded. In this work we explore ways to use these interference effect in a

functional way by a combination of theoretical and experimental methods. This should lead to single-

molecule devices with more functionality than is currently achieved.

The current consensus is that destructive quantum interference occurs in cross-conjugated

molecules, while linearly conjugated molecules exhibit constructive interference. We have

performed a combined experimental and theoretical study of photoinduced charge transfer in donor-

bridge-acceptor systems These studies show that hole transfer is ten times faster through a cross-

conjugated biphenyl bridge than through a linearly conjugated biphenyl bridge. Electronic structure

calculations reveal that the surprisingly low hole transfer rate across the linearly conjugated biphenyl

bridge is caused by the presence of destructive instead of constructive interference. We demonstrate

that the specific molecular orbital symmetry of the involved donor and acceptor states leads to

interference conditions that are different from those valid in single molecule conduction

experiments. Furthermore, the results indicate that by utilizing molecular orbital symmetry in a

smart way new opportunities of engineering charge transfer emerge.[1,2]

In addition, quantum interference effects do not only appear when considering transport through a

single conjugated molecule, but are also encountered in p-stacked systems. In a single-molecule

conductance experiment, we have shown the occurrence of clear quantum interference effect in the

conductance through a dimer of two conjugated molecules connected between two electrodes.

These interference effects can be manipulated by mechanically altering the pi-stacking configuration

by moving the electrodes with respect to each other.[3]

[1] Natalie Gorczak, Nicolas Renaud, Simge Tarkuç, Arjan J. Houtepen, Rienk Eelkema, Laurens D. A.

Siebbeles, and Ferdinand C. Grozema, Chem. Science, 6 (2015) 4196-4206.

[2] Natalie Gorczak, Nicolas Renaud, Elena Galan, Rienk Eelkema, Laurens D. A. Siebbeles and

Ferdinand C. Grozema, Phys. Chem. Chem. Phys., 18 (2016) 6773-6779.

[3] R. Frisenda, V. Jansen, F.C. Grozema, H.S.J. van der Zant and N. Renaud, Nature Chem., 8 (2016)

1099-1104.

This is the last line of your abstract.

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NewNIR-LEDs, NIR Lasers with Line-Shaped Fokus and Functionalized Cyanines Facilitate Synthesisof Tailor Made Polymers and Their Use in Industry 4.0 Related Applications

Bernd Strehmel,Christian Schmitz, Ceren Kütahya, Yulian Pang

Niederrhein University of Applied Sciences, Institute for Coatings and Surface Chemistry,Department of Chemistry, Adlerstr. 1, D-47798 Krefeld, Germany

Nowadays, near-infrared radiation (NIR) can be found in some industrial applications on large scale operating on Industry 4.0 standards. This is digital imaging based on a digital workflow, laser welding or laser drying of coatings[1]. The significant lower scattering of photons compared to UV light, the opportunity to embed functional materials covering the absorption in the UV and visible part, and the capability for excitation with semiconductor NIR-lasers enabling the possibility for spatial-resolved excitation in lithographic applications can be seen as essential benefits of operating with NIR radiation. Recently, development of photopolymer formulations based on radical and cationic crosslinking has started using a High Throughput Formulation Screening line resulting in development artificial intelligence for coating applications. Functionalized cyanines covering their absorption between 700-1000 nm have become attractive absorbers/sensitizers in combination with either semiconductor lasers exhibiting line-shaped focus (lem = 980 nm, 808 nm) and/or new NIR-LED devices available since this allows selective spatial and modulated ON/OFF excitation. A new NIR-LED device has been available as compact prototype (Phoseon Ltd.) exhibiting an emission at 805 nm with outstanding intensity. Several systems comprising an absorber/sensitizer and radical initiator were evaluated regarding their capability to crosslink multifunctional (meth)acrylic derivatives. We report also about the first successful NIR-sensitized cationic photopolymerization experiments using oxiranes in combination with functionalized cyanines. Such LED-device types may also help to substitute oven processes because such functionalized absorbers mostly deactivate radiationless with a yield >85%. Further examples demonstrate how the combination of physical (melting of powder coating[2], evaporation of water in aqueous dispersions) and chemical (crosslinking by photopolymerization) drying with NIR absorbers possess the capability to form solid films on even heat sensitive substrates using NIR-lasers with line-shaped focus. Specific structural motifs in the cyanine moiety move the system in both directions; that is physical and chemical drying. Photophysical data helped to understand the specific function of the cyanine pattern[1,2]. In addition, NIR sensitizers functioned well in photocatalytic systems for polymer synthesis using [Cu(TMPA)]

2+ at the ppm scale[3]. This gave access to block copolymers with narrow dispersity using

a photoreactor equipped with NIR-LEDs emitting at 790 nm. This system exhibited a high photostability using alkylbromides as initiator. Particular cyanines comprising a barbital group in the meso-position successfully worked in this framework. In general, this synthetic way may be applicable to manufacture crosslinked materials with narrow distribution of network junction distance. Systems based on NIR photosensitized copper catalyzed azide-alkyne click chemistry complement these investigations.

References [1]C. Schmitz, D. Oprych, C. Kütahya, B. Strehmel, NIR Light for Initiation of Photopolymerization, in Photopolymerisation Initiating Systems (Eds.: J. Lalevée, J.-P. Fouassier), Royal Society of Chemistry, 2018,pp. 431-478. [2]C. Schmitz, B. Strehmel, ChemPhotoChem 2017, 1,26-34. [3]C. Kütahya, C. Schmitz, V. Strehmel, Y. Yagci,B. Strehmel, Angew. Chemie 2018, 130,8025-8030.

Functional π-Electron Systems14th International Symposium on

Abstracts Poster Presentation

Plenary Lectures

Friday, June 7th

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A polymer synapse for low-power neuromorphic computing -mandatory blank line-

Alberto Salleo -mandatory blank line-

Department of Materials Science and Engineering, Stanford University,Stanford CA 94305 -mandatory blank line-

The brain can perform massively parallel information processing while consuming only ~1- 100 fJ per synaptic event. Two-terminal memristors based on filament forming metal oxides (FFMOs) or phase change memory (PCM) materials have recently been demonstrated to function as non-volatile memory that can emulate neuronal and synaptic functions. Despite recent progress in the fabrication of device arrays however, to date no architecture has been shown to operate with the projected energy efficiency while maintaining high accuracy. A major impediment still exists at the device level, specifically, a resistive memory device has not yet been demonstrated with adequate electrical characteristics to fully realize the efficiency and performance gains of a neural architecture. I will describe a novel electrochemical neuromorphic device (ENODe) that switches at record-low energy (<0.1 fJ projected, <10 pJ measured) and voltage (< 1mV, measured), displays >500 distinct, non-volatile conductance states within a ~1 V operating range. The tunable resistance behaves very linearly, allowing blind updates in a neural network when operated with a diffusive memristor access device. We recently showed that combined with a Si access device we are able to achieve over 109

switching events with very little degradation. Furthermore, we were able to demonstrate that a moderately scaled device can undergo a read-write cycle in less than one microsecond. Finally, parallel updates in a 3x3 array are also demonstrated, a first step towards fully parallel array operation. I will discuss the basic device physics and paths towards further improvement in performance and stability in terms of scaling and materials requirements.

Development of Redox Dopants for Organic Semiconductors and Interface

Modification

Seth R. Marder

School of Chemistry and Biochemistry, School of Materials Science and Engineering, and

Center for Organic Photonics and Electronics, Georgia Institute of Technology, Atlanta, GA

30332-0400 USA

Organic semiconductors and hybrid/organic materials have attracted interest for electronic

applications due to their potential for use in low-cost, large-area, flexible electronic devices. Here

we will report on recent developments pertaining to both n- and p-dopants that could impact the

charge injection/collection processes in organic light emitting diodes, organic field effect

transistors, and organic photovoltaic and hybrid organic/inorganic perovskite devices, as well as

on the bulk conductivity of doped semiconductors. We will consider the synthesis of new dopants

and studies to illustrate the mechanisms by which the dopants react with organic semiconductors.

The development of organic and metallo-organic-based dimers as n-dopants will also be

discussed. We will highlight the application of n-dopants for reaction with polymers that lead to

exceptionally high conductivities for n-doped systems and may have interesting thermoelectric

performance.

Selected References:

1. “n-Doping of Organic Electronic Materials using Air-Stable Organometallics,” Adv. Mater. 24 (5), 699-

703 (2012). DOI: 10.1002/adma.201103238

2. “Modification of the fluorinated tin oxide/electron-transporting material interface by a strong

reductant and its effect on perovskite solar cell efficiency.” Mol. Syst. Des. Eng. 3, 741-747 (2018). DOI:

10.1039/C8ME00031J

3. “Controllable, Wide-Ranging n-Doping and p-Doping of Monolayer Group 6 Transition-Metal Disulfides

and Diselenides.” Adv. Mater. 30, 1802991 (2018). DOI: 10.1002/adma.201802991

4. “Beating the thermodynamic limit with photo-activation of n-doping in organic semiconductors.” Nat.

Mater. 16, 1209/1-9 (2017). DOI: 10.1038/nmat5027

Functional π-Electron Systems14th International Symposium on

Abstracts Poster Presentation

Invited Lectures

Friday, June 7th

Conductivity of small-moleculeorganic semiconductors

Karl Leo

Dresden Integrated Center for Applied Physics and Photonics (IAPP), TU Dresden, 01062 Dresden, Germany, www.iapp.de

Organic semiconductors with conjugated electron systems are currently intensively investigated for many novel electronic and optoelectronic applications. Their key advantages are flexibility, low cost, and low resource usage since the mostly carbon-based materials are fabricated in nano-meter scale thin film devices. Controlled electrical doping /1/ is a key technology for efficient OLEDs and hence broadly commercially used, despite the fact that the microscopic mechanisms have been controversially discussed. In this talk, I will summarize research findings on controlled molecular doping. The detailed understanding of doping effects and Fermi level control has turned out to be difficult. A particular challenge is that the elementary charge-transfer and release process of doping can be very efficient despite the fact that the Coulomb binding energy between carrier and dopant seems much too large in organic materials to allow efficient release. Recently, we have shown that the basic mechanisms of doping in organics can be explained by including defects and disorder into the description /2/. Activation energies as low or even lower as those observed in doped inorganic semiconductors like silicon are possible. For many applications, however, the key parameter is not the charge carrier generation efficiency, but the conductivity achieved by doping and in particular the activation energy of the conductivity, which should be as low as possible. In a recent study /3/, we have comprehensively studied these parameters and related them to the molecular structures.

/1/ K. Walzer et al., Chem. Rev. 107, 1233 (2007) /2/ M. Tietze et al., Nature Comm. 9, 1182 (2018) /3/ M. Schwarze et al., Nature Materials 2019, DOI: 10.1038/s41563-018-0030-8

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Subphthalocyanines and related compounds: Singular aromatic non-planar molecules

Tomás Torres1,2,3

1Departamento de Química Orgánica, Universidad Autónoma de Madrid, Cantoblanco, 28049 Madrid,

Spain. 2 IMDEA-Nanociencia, c/Faraday 9, Campus de Cantoblanco, 28049 Madrid, Spain. 3Institute

for Advanced Research in Chemical Sciences (IAdChem), Universidad Autónoma de Madrid,

Cantoblanco, 28049 Madrid, Spain, tomas.torres@uam.es

Among the molecular building blocks used for the construction of light-powered, electroactive ensembles, subphthalocyanines (SubPcs) hold a privileged position due to their outstanding photophysical properties [1,2]. These singular cone-shaped, aromatic molecules show a strong absorption in the 550-650 nm region with excitation energies above 2.0 eV, high fluorescence quantum yields, a rich redox chemistry, and low reorganization energies. Recently, SubPcs have been used as non-fullerene acceptors in bulk heterojunctions (BHJ) solar cells [2f]. On the other hand as part of our systematic investigation in the preparation and study of novel SubPc-based D–A systems, we have used 1,1,4,4-tetracyanobuta-1,3-diene (TCBD) as partner for SubPcs. Columnar aggregates based on chiral SubPcs have been also prepared, giving rise to ferroelectric self-assembled molecular materials showing both rectifying and switchable conductivity [2a,h]. These chromophores have been incorporated in multicomponent systems showing a panchromatic response and allowing the tuning and controlling intramolecular FÖRSTER Resonance Energy Transfer for Singlet Fission [2i]. During this talk an overview of the results obtained by our group in Madrid will be given.

[1] C. G. Claessens, et al., Chem. Rev. 114, 2192 (2014). [2] a) J. Guilleme, et al., Angew. Chem. Int. Ed. 54, 2543 (2015). b) M. Rudolf, et al. Chem. Sci. 6, 4141 (2015). c) K. Cnops, et al. J. Am. Chem. Soc. 137, 8991 (2015). d) J. Guilleme, J. et al., Chem. Commun. 52, 9793 (2016). e) M. Urbani, et al., Chem. Asian J. 11, 1223 (2016). f) C. Duan, et al., Angew. Chem.

Int. Ed. 56, 148 (2017). g) K. A. Winterfeld, et al., J. Am. Chem. Soc., 139, 5520 (2017). h) A. V. Gorbunov, et al., Science Advances 3, e1701017 (2017). i) G. Lavarda, et al., Angew. Chem. Int. Ed. 57, 16291 (2018).

Functional π-Electron Systems14th International Symposium on

Abstracts Poster Presentation

Contributed Lectures

Friday, June 7th

Q R>~ - ~ N-0--0-N -~ b

H -c71 ~--~-' .. / .. • ·······················:

Carrier mobility measurement by MIS-CELIV method in hole-transport material

for organic light-emitting diodes

Ken-ichi Nakayama, Yuna Suzuki, Sho Adachi, Keitaro Yamada, Tomoyoshi Suenobu, Mitsuharu Suzuki

Department of Material and Life Science, Graduate School of Engineering, Osaka University,

Suita, Osaka (Japan).

Organic electronic devices such as organic light-emitting diodes and organic solar cells generally have vertical device structure, where the organic semiconductor film is sandwiched by the two electrodes. The carrier mobility in perpendicular to the film surface (vertical direction) is important for improving the device performances, e.g. low voltage operation, high efficiency and high frequency response. There have been several techniques to evaluate the carrier mobilities in organic semiconductors; space-charge limited current (SCLC) method has been widely used as a standard technique for thin organic films; however, it requires a strict ohmic contact and is easily affected by the carrier injection interface.

Injection-charge extraction by linearly increasing voltage in metal-insulator-semiconductor structures (MIS-CELIV) is a new method for evaluating carrier motilities of thin films.[1] The mobility is estimated from the current transients by extraction of accumulated charges at the MIS interface. In the past few years, it has been mainly used for evaluating the mobility balance between holes and electrons in blend films consisting of conjugated polymer and fullerene, for OPVs. However, the validity of the absolute value of the estimated mobility has not been verified. In this study, we applied the MIS-CELIV for hole mobility measurement of N,N’-Bis(naphthalen-1-yl)-N,N’-bis(phenyl)-benzidine (NPB), which is a standard hole-transporting material for organic light-emitting diodes. We carefully measure the hole mobilities under various conditions and compared them with those obtained from the conventional SCLC method.[2]

Figure 1 shows typical responses of MIS-CELIV measurements for a Si/SiO2/NPB/MoO3/Al device. Ideal transient currents in agreement with the theory were observed in the NPB film. The hole mobility estimated from the transient time showed good agreement with the SCLC mobility, including electric field dependence. These results indicate that the MIS-CELIV method can be used as a standard technique to evaluate the carrier mobility in organic thin films. The required conditions for valid measurements are also discussed.

(a) (b)

InsulatorElectrode

Oscilloscope

R

FunctionGenerator

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accumulated charges

Voltage

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Time (ms)Fig. 1. (a) Measurement setup of the MIS-CELIV method. (b) Typical resnposes of the MIS-CELIV for a NPB film with different charging voltages.

[1] G. Juska, N. Nekrasas, and K. Genevicius, J. Non-Cryst. Solids 358, 748 (2012). [2] C. Katagiri, T. Yoshida, M. S. White, C. Yumusak, N. S. Sariciftci, and K. Nakayama, AIP Advances 8, 105001 (2018).

R R 1a (R = H) 1b (R,R = -CH2CHr) 1c (R,R = -CH=CH-)

16000

,; ~ 12000 "iii C ,! 8000 .!: C .. E 4000 .. er:

C-C stretching vibration v = 587 c m·1 (ethane: 993 cm·')

'· .. / 0 .,,,,_.,__,,.....,,.__,~'-""==""""""-""""""'""-"'='---'""---='

300 500 700 900 v (cm·1)

1100 1300 1500

Hyper covalent bond in highly strained hydrocarbon: an expandable C–C single bond with a bond length beyond 1.8 Å

Yusuke Ishigaki, Takuya Shimajiri, Takanori Suzuki

Department of Chemistry, Faculty of Science, Hokkaido University, Sapporo (Japan)

Highly strained hydrocarbons such as sterically-congested and/or curved polycyclic aromatic hydrocarbons as well as cyclic π-conjugated molecules have attracted much attention with regard to their unique properties. We focused on the Csp3-Csp3 bond, whose standard length is 1.54 Å. Upon seeking for extreme structures with the long C-C bond, there have been three types of approaches: (i) diamondoid dimers [1], (ii) clamped hexaphenylethanes [2], and (iii) diaminocarboranes [3]. The first approach (i) is so direct since such dimers surrounded only by sp3 carbons dissociate into two open-shell species when the long C-C bond is broken. In the second approach (ii), there are only sp2

carbons around the long C-C bond. The C-C bond cleavage seldom happens due to the intramolecular process to give diradical species. The third approach (iii) including the hyperconjugation is quite different from former two types because the long C-C bond is surrounded only by heteroatoms.

Based on the second approach (ii), we propose a new tactic that can stabilize the compounds with an elongated bond by adopting the intramolecular "core-shell strategy"; the weakened Csp3-Csp3

bond (core) is protected by the shape-persistent and chemically inert Csp2 fused rings (shell). Based on this strategy we synthesized dispiro(dibenzocycloheptatriene)s 1a-1c, for which all degradation processes of the weak Csp3-Csp3 bond are hampered to enable their isolation as stable entities. The optimized (M06-2X/6-31G*) and observed structures showed the less symmetrical bent geometry for the two spiro rings of the "shell" structure, which is the outstanding structural feature of 1a-1c. The determined bond length of 1.806(2) Å in 1c (Fig. 1) is the greatest among the values reported to date for the neutral hydrocarbons. The presence of the covalent bond in 1c was confirmed experimentally by detailed X-ray analyses and by Raman spectroscopy (Fig. 2). Because the observed bond length is greater than the shortest non-bonded intramolecular C···C contact [1.80(2) Å] [4], the covalently bonded state and non-bonded state are seamlessly connected in terms of the interatomic distance. Thus, it is highly likely that we could find an even longer C-C bond (''hyper covalent bond'' with a bond length of 1.8-2.0 Å) under the proper molecular design following the intramolecular "core-shell strategy" [5]. Compounds with the "hyper covalent bond" are promising candidates to make a novel class of materials, whose crystals, films, or polymers can respond to the external mechanical stimuli with anisotropic contraction or expansion of the matter, accompanied by reversible compressing, extending, or breaking the "bond" in the molecule.

1.806(2) Å

Figure 1. ORTEP drawing of 1c at 400 K.

Figure 2. A Raman spectrum measured by using a single crystal of 1c at 298 K.

[1] P. R. Schreiner and A. A. Fokin et al., Nature 477, 308-311 (2011). [2] T. Takeda and T. Suzuki et al., Chem. Lett. (Highlight Review), 42, 954-962 (2013).

[3] Z. Li, X.-Q. Xiao, and T. Müller et al., Angew. Chem. Int. Ed. doi: 10.1002/anie.201812555 (Early View). [4] J. L. Adcock, A. A. Gakh, J. L. Pollitte, C. Woods, J. Am. Chem. Soc. 114, 3980-3981 (1992).

[5] Y. Ishigaki, T. Shimajiri, T. Takeda, R. Katoono, T. Suzuki, Chem 4, 795-806 (2018).

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Epitaxial growth and anisotropic properties of uniaxially oriented thin films utilizing polymorphic alkyl‐substituted phthalocyanines

Akihiko Fujii1, Takahiro Kitagawa1, Mitsuhiro Nakatani1, Shusaku Nagano2, and Masanori Ozaki1

1Graduate School of Engineering, Osaka University, Osaka (Japan) 2Nagoya University Venture Business Laboratory, Aichi (Japan)

Molecularly oriented thin films of non‐peripherally alkyl‐substituted phthalocyanines (CnPcH2) and tetrabenzotriazaporphyrins (CnTBTAPH2), which exhibit the crystal polymorphs [1], were fabricated by the bar‐coating method [2,3] and contact freezing method [4,5]. By setting a seed crystal onto the substrate as a nucleus, the homo‐ or hetero‐epitaxial growth in the thin film could be selectively realized [6].

CnPcH2 and CnTBTAPH2 are liquid crystalline (LC) organic semiconductor materials, which demonstrate the high ambipolar mobility [7,8] and are promising as a donor material for organic solar cells [8‐10]. In the bar‐coating method using CnPcH2, which exhibits two crystal polymorphs, α‐type and β–type crystals [1], setting either seed crystal onto the substrate in advance, the bar‐coated film involved with the homo‐epitaxial growth could be uniformly generated [6]. The optical anisotropy and molecular step/terrace surface of the thin film were observed by polarized spectroscopy and atomic force microscopy, respectively. The three‐dimensional molecular packing structure in the thin film was determined by the grazing‐incidence wide‐angle X‐ray scattering (GIWAXS) method.

The contact freezing method was also adopted to fabricate the highly molecular‐oriented thin films of CnPcH2 and CnTBTAPH2. By applying a thermal stimulation to a supercooled LC states of CnPcH2 and CnTBTAPH2, the phase transition, that is, freezing phenomenon, spontaneously occurs to the in‐plane direction of the thin film [4,5]. Dropping the CnTBTAPH2 seed crystal onto the supercooled LC state film, the crystal‐phase film with the same crystal structure generated. Using the CnPcH2 seed crystal for the contact freezing of CnTBTAPH2, the hetero‐epitaxial growth was realized, that indicates the appearance of an unidentified crystal polymorph for CnTBTAPH2, and were discussed by taking the single crystalline structure reported previously [1,11] into consideration.

This work was partially supported by the JSPS KAKENHI (18H04514, 17K18882) and the JSPS Core‐to‐Core Program, A. Advanced Research Networks. [1] M. Ohmori, C. Nakano, A. Fujii, Y. Shimizu, and M. Ozaki, J. Cryst. Growth, 468, 804 (2017). [2] M. Ohmori, T. Uno, M. Nakatani, C. Nakano, A. Fujii, and M. Ozaki, Appl. Phys. Lett., 109, 153302

(2016). [3] M. Ohmori, M. Nakatani, H. Kajii, A. Miyamoto, M. Yoneya, A. Fujii, and M. Ozaki, Jpn. J. Appl.

Phys., 57, 03EH10 (2018). [4] M. F. Ramananarivo, T. Higashi, M. Ohmori, K. Sudoh, A. Fujii, and M. Ozaki, Appl. Phys. Express, 9,

061601 (2016). [5] T. Kitagawa, M. F. Ramananarivo, A. Fujii, and M. Ozaki, Jpn. J. Appl. Phys., 57, 04FL09M (2018). [6] Nakatani, M. Ohmori, S. Nagano, A. Fujii, and M. Ozaki, Org. Electron., 62, 241 (2018). [7] Y. Miyake, Y. Shiraiwa, K. Okada, H. Monobe, T. Hori, N. Yamasaki, H. Yoshida, M. J. Cook, A. Fujii,

M. Ozaki, and Y. Shimizu, Appl. Phys. Express, 4, 021604 (2011). [8] Q.‐D. Dao, K. Watanabe, H. Itani, L. Sosa‐Vargas, A. Fujii, Y. Shimizu, and M. Ozaki, Chem. Lett., 43,

1761 (2014). [9] T. Hori, Y. Miyake, N. Yamasaki, H. Yoshida, A. Fujii, Y. Shimizu, and M. Ozaki, Appl. Phys. Express,

3, 101602 (2010). [10] Q.‐D. Dao, L. Sosa‐Vargas, T. Higashi, M. Ohmori, H. Itani, A. Fujii, Y. Shimizu, and M. Ozaki, Org.

Electron., 23, 44 (2015). [11] C. Nakano, M. Ohmori, N. Tohnai, A. Fujii, and M. Ozaki, J. Cryst. Growth, 468, 810 (2017).

Host Dopant

(a)

t+~--t+

Host Dopant

(b)

The Effect of Energy Levels on Doping processes in Organic Semiconductors

Ross Warren1, Alberto Privitera1, Jenny Nelson2, Moritz Riede1

1Department of Physics, University of Oxford, Oxford, OX4 1FQ, (UK) 2Department of Physics, Imperial College London, London, SW7 2AZ, (UK)

Molecular p- and n-doping of organic semiconductors has been key for the successful commercialisation of OLEDs and been used also to improve the performance of organic solar cells and transistors. The advantage of using a doped transport layer in a device is that the voltage losses can be reduced through an increase in conductivity. Furthermore, an increase in the charge carrier density reduces the barrier for tunnel injection at the metal contacts. Despite the success of dopants in OLEDs, the doping efficiency remains very low as compared to the inorganic counterpart and critically the fundamental mechanism of the doping process is still under debate.

Figure 1. A simple schematic illustrating the common assumption of a host and dopant pair with (a)

favourable (b) unfavourable energetic offset for p-type doping.

The prevailing practice for pairing hosts and dopants is based on favourable energy-level alignment. For p-doping, this involves introducing a molecule with an electron affinity (EA) greater than that of the host molecule’s ionisation potential (IP) such that it is energetically favourable for one electron transfer from the host’s highest occupied molecular orbital (HOMO) to the dopant’s lowest unoccupied molecular orbital (LUMO) as shown in figure 1a. This mechanism is described as integer charge transfer or ion-pair formation. [1]

In this contribution we present the effect of the energy-level offset from favourable to the unfavourable case, as shown in figure 1b, on the efficiency of charge transfer between the host and dopant. We used zinc phthalocyanine (ZnPc) and its fluorinated derivatives Fx-ZnPc, x= 4, 8, 16, as host semiconductor and co-evaporated it with the p-type dopant F6-TCNNQ. We probed the effects of doping via electron paramagnetic resonance, photo thermal deflection spectroscopy and conductivity measurements and observe how the doping efficiency changes as function of the energy level of the host. We compare our experimental data to a statistical model based on work by Tietze et al. [2] in order to unravel how the doping process depends on energetic offset and improve the current understanding of how doping in organic semiconductors works.

[1] I. Salzmann, G. Heimel, M. Oehzelt, S. Winkler, N. Koch, Acc. Chem. Res., 49, 370−378 (2016) [2] M. Tietze, J. Benduhn, P. Pahner, B. Nell, M. Schwarze, H. Kleemann, M. Krammer, K. Zojer, K.

Vandewal, K. Leo, Nat. Comms, 9, 1182 (2018)

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Self-Assembled Phe-PheDipeptideDoped withLuminescentCompounds:Tunnable Photophysical Characteristics

TatianaMartins1,Geovany Sousa1,Diericon Cordeiro1,Ramon Miranda

1,Lucas Fernandes1

1Chemistry Institute,1Federal University of Goias,Goiania (Brazil)

Self-assembled peptidenanostructures areeasily prepared through supramolecular approaches that enable the control of the final structures. In particular, peptides containing at least one diphenylalanine unit have presented electro-optical properties that can be exploited in several electron transfer processes, such asenergyconversion, in electro-optical devices, and sensing. They also present good morphological properties that enable them to be employed in drug delivery, encapsulation, as templates for metallic nanowires and other metallic nanostructures. Also, due totheirchemical stability, biocompatibilitygood morphological characteristics, the ease of preparation in liquid medium and because they can be thought to present any desired property, including electro-optical properties, they have been combined to electroluminescent materials and to perovskite, topresent new andunique photophysical andmorphological properties. When used as additives of thin films of organic polymers and molecules, they affect the energy transferprocesses thatoccurin such systems and give rise to the energetic processes thatpromote,

for instance, the photovoltaic effect in the active layers of solar cells. In this work, nanotubes and nanovesicles of diphenylalanine were combinedtothinfilms of poly(2-metoxy-5-(2´-ethylhelyloxy)-p-

phenylene-vinylene) - (MEH-PPV), polyvinylcarbazole (PVK) and LBL films of rubrene, 9-vinyl-carbazole, coumarin-6and anthraceneto generatenew materials that were deposited on lead-free perovskite thinfilms. The photophysical properties of suchcombinations are determinedby steady-state fluorescence spectroscopy, time-resolved fluorescence spectroscopy and by fluorescence lifetime imaging microscopy (FLIM) and their morphological characteristics were determined by scanning electronicmicroscopy and fluorescence microscopy. These techniques give information to enable the understanding of the conformational orientation and specific interactions between the self-assembled structureand theelectroluminescent compounds, which areindispensable toensure the rightapplication ofsuch materials. Computational simulations were also performedtogive the energies of the electronic excited states of MEH-PPV, PVK, rubrene, anthracene and perovskite in order toevaluate the transitionenergies andtocharacterize the excited states, in thesecompounds, that would participate in singlet exciton fission processes and contribute to a more efficientphotovoltaic device.

OFETs subst rate

Increased reaction si tes ... i -60 :f_30

! OOppm ,....,, - WIIM>R• - wlopore•

1 ppm

50 100 160 Time(s)

1ilmi:17i.::~ -:-.:::· I -~ I I' I\ ~ = I • I f/liil /~' ' I ., I ~

:1 i f ~ 1D~ant 1 " .. " " " ________ .) F••TCNQ (mgl m L)

1 Solution-Processed Nanoporous Organic Thin Film Transistors 2 3 Fengjiao Zhang1,2, Ge Qu1, Erfan Mohammadi1, Jianguo Mei3, Ying Diao1

4 5 1 Department of Chemical and Biomolecular Engineering, University of Illinois Urbana-Champaign,

6 600 S. Mathews Ave., Urbana, IL 61801, USA

7 2 School of Chemical Science, University of Chinese Academy of Sciences, Beijing 100049, P.R. China

8 3 Department of Chemistry, Purdue University, 560 Oval Drive, West Lafayette, Indiana 47907, United

9 States

10 11 Organic semiconductors, distinguished by their intrinsically chemical versatility, solution 12 processibility and mechanical flexibility, offer an excellent platform for the application for organic 13 field-effect transistors (OFETs), solar cells, thermoelectrics, chem-/biosensors and electronic skins.[1] 14 OFETs based chemical sensing and doping has been widely used in constructing high-performance 15 circuits and low-cost detectors, due to their portability, ability for high-throughput manufacturing 16 and unique electric properties. However, OFET-based chemical sensors are rarely applied to 17 personalized health and environmental monitoring via detection of volatile organic compounds 18 (VOCs), due to the stringent requirements of ultrahigh sensitivity (ppb level), rapid response and 19 resilience to temperature and humidity fluctuations. What’s more, it remains a challenge to 20 effectively dope the conductive channels of highly crystalline devices. 21 In our work, we develop meniscus-guide-coating nanoporous OFETs to address these challenges. 22 This approach yields nanopores with tunable pores size (50 nm-700 nm) in the semiconductor thin 23 film via simple meniscus-guide coating processing. Introducing nanopores grants direct access to the 24 highly reactive sites otherwise buried in the conductive channel, thereby imparting ultra-sensitivity 25 to analytes and dopants (Figure 1).[2, 3] Using this strategy, we obtain unprecedented ultrasensitive, 26 ultrafast chemical sensing to VOCs down to the 1 ppb level at hundred-millisecond time scale, which 27 opens up a wide range of applications in personalized health and environmental monitoring.[2] The 28 nanopore-induced reaction sites increase enhance the doping effect without causing structural and 29 energetic disorders.[3] For instance, the apparent hole mobility of highly-crystalline C8-BTBT

2V-130 increased by almost sevenfold to 18.2 cm s-1, while the nonporous C8-BTBT hardly increased upon 31 doping. We further demonstrate flexible sensor chip for real-time monitoring of breath ammonia-a 32 potential biomarker for chronic kidney disease, Alzheimer's disease etc.

33

34 Figure 1 Schematic illustration of meniscus-guide coated nanoporous films and their use for sensitive gas

35 sensor and effective chemical doping

36 References 37 [1]. C. A. Di, F. J. Zhang, D. B. Zhu, Adv. Mater. 25, 313-330 (2013).

38 [2]. F. J. Zhang, G. Qu, E. Mohammadi, J. G. Mei and Y. Diao, Adv. Funct. Mater. 27, 1701117 (2017).

39 [3]. F. J. Zhang, X. J. Dai, W. K. Zhu, H. Chung and Y. Diao, Adv. Mater. 29, 1700411 (2017).

1 ElectricalandThermalTransportPropertiesof Chalcogenophene Copolymers: Exploring 2 the Effects of Monomers and Dimers from Furan to Tellurophene 3 4 James F. Ponder Jr.1, Helen Bristow1, Cameron Jellett1, Chen Chen,2 Maxime Babics1, Mark S. Little1, 5 Iain McCulloch1,3

6 7 1

Department of Chemistry, Imperial College London,London (UK), 2Department of Physics,University 8 of Cambridge, Cambridge (UK) 3Division of Physical Sciences and Engineering, 9 King Abdullah University of Science and Technology,Thuwal (Saudi Arabia)

10 11 Thiophene has served as the core heterocycle for the majority of organic electronic (OE) research in 12 recent years. This is primarily due to its stability and well understood synthetic reactivity. 13 Substitution of the sulfur atom for another chalcogen atom (oxygen, selenium, or tellurium) results in 14 heterocycles with unique properties. Selenophene-based materials have received a great deal of 15 interest in the field of OE due to their differences and similarities to the more widely studied and 16 understood thiophene analogs. [1] Alternatively, furan and tellurophene-based materials have 17 received significantly less attention, primarily due to the perceived instability of furans and the 18 difficulties in synthesis of tellurophenes. [2, 3] However, these chalcogenophenes all show reduced 19 aromatic character compared to thiophene and materials containing them show increased planarity 20 and quinoidal character. This has been shown to change the optoelectronic properties of these 21 materials relative to the thiophene counterparts. Additionally, incorporation of heterocyclic dimer 22 units into a structure, as opposed to the single units, has been shown to result in unexpected 23 properties, even when the overall percent composition of the backbone remains unchanged. [4, 5] 24 Here we report a family of copolymers containing the chalcogenophene monomers and dimers with 25 an alkylated bithiophene unit providing solubility (Figure 1). 26 The optical, electrochemical, and thermal properties of these materials are analyzed and differences 27 in the long-range order are probed using a variety of methods. Following chemical doping, the solid-28 state electrical conductivity values of these polymers are compared to elucidate the effect of the 29 atom substitution and role of monomer vs. dimer units. Organic field effect transistors (OFETs) are 30 also used to probe these structural differences. The well studied polymer PBTTT is directly compared 31 to the copolymer family to provide meaningful context to the scientific literature. Finally, the 32 relevance of these findings to other polymer systems, including donor-acceptor systems, is 33 presented. 34 35

R R

S S S S X S X n S X Sn

S

R R

X = O , S , Se , Te 36 37 Figure 1. Structures of the chalcogenophene copolymer backbone. 38 39 [1] J. Hollinger, D.Gao, D.S.Seferos, Isr. J. Chem., 54,440. (2014) 40 [2] X. Jin, D. Sheberla, L. J. W. Shimon,M. Bendikov, J. Am. Chem. Soc., 136, 2592. (2014) 41 [3] E. I. Carrera, D. S. Seferos, Macromolecules, 48,297. (2015) 42 [4] O. Gidron, N. Varsano, L. J. W. Shimon, G. Leitus, M. Bendikov, Chem. Commun., 49,6256 (2013) 43 [5] J. F. Ponder Jr., A. M. Österholm, J. R. Reynolds, Macromolecules, 29,2106. (2016)

1

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+/ 'f1fRIVS

Development of Hybrid Materials based on Organic Semiconductors

and Carbon Nanostructures or Inorganic Nanoparticles

Stefania Aivali,1

Charalampos Anastasopoulos,1

Christos Charalampopoulos,1

Aikaterini K. Andreopoulou,1,2

Joannis K. Kallitsis1,2

1 Department of Chemistry, University of Patras, Patras, Greece

2 Foundation for Research and Technology Hellas, Institute of Chemical Engineering Sciences

(FORTH-ICE-HT), Patras, Greece.

Various semiconducting polymeric and hybrid materials that fulfill specific requirements for their application in organic bulk heterojunction (BHJ-OPVs) and dye sensitized (DSSCs) photovoltaics are presented herein. In the BHJ-OPVs case, end or side functionalized polymer electron donors have been developed and used to create either copolymers having both electron donor and acceptor functionalities in an attempt to control and stabilize the morphology in bulk heterojunction solar cells, or new hybrid nanomaterials based on carbon nanostructures like fullerene derivatives.

Organic Sensitizer TiO2

semiconductors -fullerenes

semiconductors -inorganic NPsHYBRIDS

Special attention is given to the direct covalent connection of the polymeric segment onto the carbon nanostructures in order to preserve and enhance their electronic interaction.[1-4] For DSSCs, properly end functionalized polymeric semiconductors that are able to act as polymeric dyes have been connected onto the hydroxyl decorated surface of inorganic semiconductor nanoparticles (e.g. Titanium Oxide - TiO2) resulting in non-hydrolysable organic-inorganic hybrids as alternative photoanodes for dye sensitized solar cells.[5, 6] A detailed study of the influence of the chemical structure on the materials optical, electronic and morphological properties has been performed in order to evaluate the different materials and find the more promising ones and can be used for solar cell preparation and testing.

Acknowledgments: Financial support from the project: "Research and Development Plan of Efficient and Low Cost Photovoltaic (P/V) Glass Panels, BRITE-PVGlass" (FR/MIS: 80399/5021436) of the “Supporting Small and Medium Enterprises for research projects in the fields 'Microelectronics' and 'Advanced Materials' (1b.1.1) of the Operational Program “WEST GREECE 2014-2020” co-funded by Greece and the European Union, is greatly acknowledged.

References:

[1] S.Kakogianni, S.N. Kourkouli, A.K. Andreopoulou, J.K. Kallitsis, J. Mater. Chem A, 2, 8110 (2014). [2] S. Kakogianni, M.A. Lebedeva, G. Paloumbis, A.K. Andreopoulou, K. Porfyrakis, J.K. Kallitsis, RSC

Adv, 6, 98306 (2016). [3] S. Kakogianni, A.K. Andreopoulou, J.K. Kallitsis, Polymers, 8, 440 (2016). [4] S. Aivali, S. Kakogianni, C. Anastasopoulos, A.K. Andreopoulou, J.K. Kallitsis, Nanomaterials, In Press (2019). [5] P. Giannopoulos, A. Nikolakopoulou, A.K. Andreopoulou, L. Sygellou, J.K. Kallitsis, P. Lianos, J

Mater. Chem. A, 2, 20748 (2014). [6] P. Giannopoulos, D. Raptis, K. Theodosiou, A.K. Andreopoulou, C. Anastasopoulos, A. Dokouzis, G. Leftheriotis, P. Lianos, J.K. Kallitsis, Dyes & Pigments, 148, 167 (2018).

_;8ysJ /-- ~ ~-(--~,> \ ___ j Br , ___ ;'

Twofold j R-NH2 Buchwald-J:lartwig R = I alkyl

Coup/mg ary '

Double Lithiation j Double Transmetalation

Twofold Negishi Coupling

s s s (hetero )ary1-J( )[_)-(hetero )aryl

N I R

Anti aromaticity

diatropic / paratropic ring current

Redox Activity Luminescence

1 Dithieno[1,4]thiazines and Bis[1]benzothieno[1,4]thiazines – Redox Activity, Luminescence

2 Characteristics and Antiaromaticity of Novel Congeners of Phenothiazine

3

4 Thomas J. J. Müller,1* Arno P. W. Schneeweis,

1 Simone T. Hauer,

1 Catherine Dostert

1

5

6 1Institut für Organische Chemie und Makromolekulare Chemie, Heinrich-Heine-Universität Düsseldorf,

7 Düsseldorf (Germany)

8

9 Thienyl [1,2,3,4] and benzothieno anellated [1,4]thiazines [5] can be readily accessed by twofold

10 Buchwald-Hartwig aminations. These title compounds are significantly more electron rich than their

11 more familiar congeners, i.e. phenothiazines, as supported by DFT calculations and cyclic

12 voltammetry data [4]. While dithieno[1,4]thiazines are particularly interesting as strong donors due

13 to their rich organometallic one-pot functionalization chemistry [2,3], anti-anti and syn-anti

14 bis[1]benzothieno[1,4]thiazines reveal peculiar electronic properties [5]. Anti-anti

15 bis[1]benzothieno[3,2-b:2',3'-e][1,4]thiazines display pronounced green luminescence in solution (F

16 ≈ 20%) and in the solid state, while Syn-anti regioisomers are only weakly luminescent in solution,

17 but show aggregation induced emission enhancement and solid state luminescence. X-ray structure

18 analyses of anti-anti derivatives amazingly reveal coplanar arrangements of the pentacyclic anellated

19 1,4-thiazine system, emphasizing a structural similarity to heteroacenes. The calculated theoretical

20 nucleus-independent chemical shifts (NICS) additionally confirm that these 8-electron core systems

21 can be considered as the first electronically unbiased anellated 1,4-thiazines with antiaromatic

22 character. The syntheses, electronic properties and electronic structures of these novel types of

23 polyheterocyclic donors will be presented and discussed.

24

25 26

27 [1] C. Dostert, C. Wanstrath, W. Frank, T. J. J. Müller, Chem. Commun. 48, 7271 (2012).

28 [2] C. Dostert, D. Czajkowski, T. J. J. Müller, Synlett 25, 371 (2014).

29 [3] C. Dostert, T. J. J. Müller, Org. Chem. Front. 2, 481 (2015).

30 [4] A. Schneeweis, A. Neidlinger, G. J. Reiss, W. Frank, K. Heinze, T. J. J. Müller, Org. Chem. Front. 4,

31 839 (2017).

32 [5] A. P. W. Schneeweis, S. T. Hauer, G. J. Reiss, T. J. J. Müller, Chem. Eur. J. 25, (2019) doi:

33 10.1002/chem.201805085.