Organic Light Emitting Diodes: Display and Lighting Technology of

23
Organic Light Emitting Diodes: Display and Lighting Technology of the Future Karl Leo Institut für Angewandte Photophysik, TU Dresden, and Fraunhofer-Institute für Photonische Mikrosysteme, Dresden

Transcript of Organic Light Emitting Diodes: Display and Lighting Technology of

Page 1: Organic Light Emitting Diodes: Display and Lighting Technology of

Organic Light Emitting Diodes: Display and Lighting Technology of the Future

Karl LeoInstitut für Angewandte Photophysik, TU Dresden, and Fraunhofer-Institute für Photonische Mikrosysteme, Dresden

Page 2: Organic Light Emitting Diodes: Display and Lighting Technology of

Motivation: What is possible with OLED:

Samsung 40” TV display

Page 3: Organic Light Emitting Diodes: Display and Lighting Technology of

Organic Semiconductors

Photovoltaic cellsOrganic materials Integrated circuits

• Large area & flexible substrates possible

• Large variety of materials

• Low cost

Page 4: Organic Light Emitting Diodes: Display and Lighting Technology of

Small-Molecules

Organic semiconductors: Two variants

Polymers

Technology: Spin-On Technology: Evaporation

Page 5: Organic Light Emitting Diodes: Display and Lighting Technology of

pzpz

sp2 sp2

σ

σ∗

π

π∗

p lane of thesp 2-orb ita ls

pz-orb ita l π -bond

π -bond

σ -bond

pz-orb ita l

The basics of organic semiconductors:Conjugated π-electron systems

Sp2-hybridised Carbon:

Page 6: Organic Light Emitting Diodes: Display and Lighting Technology of

de loka lis ie rte π −E lektronen

pz

σ∗

sp2

6 x

18 x

LUMO (π*) => EC „conduction band“

HOMO (π) => EV „valence band“

π-electron systems delocalize!

• VdW crystals• small π−π-overlap, narrow bands• saturated electron system

delocalizedπ-electrons

Molecules with conjugated π-electron system

Technology: vapor deposition

Page 7: Organic Light Emitting Diodes: Display and Lighting Technology of

Device energy diagram

E

x

Cathode

LUMO

HOMO

Anode

Device structure

V

A

Light emission

Organic Light Emitting Diodes

OLEDs: Basic Principles

Glass substrate

Transparent anode

Emissive layer

Cathode

++ +

---≈300nm

Page 8: Organic Light Emitting Diodes: Display and Lighting Technology of

Organics Collaboration Dresden

Institut fürAngewandte Photophysik

IAPP, University of Dresden (www.iapp.de, approx. 40 people)

• Basic research on novel device concepts

• Low-voltage OLED

Fraunhofer-IPMS Dresden (www.ipms.fraunhofer.de, approx. 25 people)

• Process development with highly efficient OLEDs

• OLED-Inline-deposition set-up (30x40cm Substrate)

• Driving Electronic for OLED-Displays

• Small to medium volume fabrication

Novaled GmbH (www.novaled.com, approx. 45 people)

• Highly efficient OLED-stacks for RGB-Displays

• Technology licensing

Page 9: Organic Light Emitting Diodes: Display and Lighting Technology of

• Exponential current-voltage relation

• Flat-band under operation

• Low work-function contacts not needed !

p n

Why doped transport layers:Inorganic vs. Organic LED

Inorganic LED (e.g., GaAs/AlGaAs) Organic LED

CB

VB

EFe

EFh

Metal

• space charge limited currents

• low work function metals neededITO-preparation necessary

HTLETL

Page 10: Organic Light Emitting Diodes: Display and Lighting Technology of

Double emission layer (D-EML) structure

D-EML structure

Al

BPhen:Cs

BPhen

TAZ:Ir(ppy)3

TCTA:Ir(ppy)3

Spiro-TAD

MeO-TPD:F4-TCNQ

ITO substrate

n-doped ETL

HBL

PET-EML

PHT-EML

EBL

p-doped HTL

p-H

TL

EB

L

HB

L

EM

L2

ITO

Al

n-E

TL

EM

L1

• Self-balancing EML system• no charge accumulation at interfaces

X. Zhou et al., Appl. Phys. Lett. 81, 4070 (2002)

Page 11: Organic Light Emitting Diodes: Display and Lighting Technology of

2.6 2.8 3.0 3.210

100

1,000

10,000

Lum

inan

ce (c

d/m

2 )

Voltage (V)

1,000 cd/m2 @ 2.9V61.5 cd/A; 67 lm/W

100 cd/m2 @ 2.68V64 cd/A; 75 lm/W

Highly efficient & stable PIN Triplet OLED:World record in efficiency

G. He et al., Appl. Phys. Lett. 85, 3911 (2004)

• Highly efficient devices are also most stable devices

• Efficiency higher than for best green nitride LED

Page 12: Organic Light Emitting Diodes: Display and Lighting Technology of

Lifetime of PIN-OLEDs

OLEDAsia Seoul 2005

Current status:phosphorescent red (0.68, 0.32):100,000 h at 500 cd/m²phosphorescent green (0.38, 0.59): 25,000h at 500 cd/m² (Irppy3 based)fluorescent blue (0.15, 0.17): 6,000 h at 500 cd/m²

• Novaled pin-OLEDs have reached state of the art lifetimes for emitter systems in all three colors• samples still contain Cs as n-dopant

100 1.000 10.000

1.000

10.000

100.000

1.000.000

Life

time

/ h

Luminance / cd/m2

200,000 h @ 150 cd/m2

30,000 h @ 500 cd/m2

8,000 h @ 1000 cd/m2

n = 1.7

Red triplet pin OLED

Page 13: Organic Light Emitting Diodes: Display and Lighting Technology of

OLEDFAB Project

• OLEDFAB Projekt iniated by Thomson und BMWA/SMWA

• Novaled leads Saxonian consortium with IPMS und IAPP

• Goals: - Demo of a 5 inch active-matrive display with highly efficient pin technology- Display manufactured using novel inline technology

• Other partners: - Applied Films - Labor für Bildschirmtechnik Stuttgart- Deutsche Thomson Brandt

Page 14: Organic Light Emitting Diodes: Display and Lighting Technology of

Full color AM display based on pin technology

Performance:

operating voltage for 100cd/m2: around 7V (OLED + backplane)

power consumption:240mW@100cd/m2 (in forwarddirection only, video mode)

about 60% of equivalent LCD display

• Active matrix OLED made in joint project by ITRI (Taiwan), Thomson (France) and Novaled

• Panel emitting in both directions on n-channel LTPS backplane (3.25”, QVGA, 130dpi) based on PIN structure

OLEDFAB: Display with improved backplane in preparation

Page 15: Organic Light Emitting Diodes: Display and Lighting Technology of

Even higher Light Efficiencies: out-coupling enhancement

OLEDAsia Seoul 2005

Efficiency at 1000 cd/m²: 110 lm/W (with outcoupling enhancement)

Novaled focuses on furtherimprovement of their recordbreaking efficiencies byout-coupling enhancements(target 2005: 140lm/W)

10 100 1000 100000

20

40

60

80

100

120

Pow

er e

ffici

ency

(lm

/W)

Luminance (cd/m²)

Green phosphorescent PIN OLEDwith outcoupling enhancement

Page 16: Organic Light Emitting Diodes: Display and Lighting Technology of

Institut für Angewandte PhotophysikTechnische Universität Dresden

LED performance vs. time

1965 1970 1975 1980 1985 1990 1995 2000 2005

0

20

40

60

80

100

120

0

20

40

60

80

100

120

OLED white Red Filtered

Tungsten Bulb (unfiltered)

Fluorescent Lamp

InGaNgreen

OLED

PLED

AlInGaP Red/Yellow

Pow

er E

ffici

ency

(Lum

en/W

att)

Year

Dresden leading in both RGB and white

Page 17: Organic Light Emitting Diodes: Display and Lighting Technology of

OLED Lighting Applications

source: Philips Lighting March 2004 GE demonstrator

Signage General lighting

Page 18: Organic Light Emitting Diodes: Display and Lighting Technology of

Technology Roadmap (USDC)(Diffuse lighting)

Page 19: Organic Light Emitting Diodes: Display and Lighting Technology of

OLLA project

• OLLA EU 6th Framework Integrated Project initiated by Philips

• OLLA: Organic LED for Lighting Applications

• Aims:- Highly Efficient white OLED- Large Area OLED- Low-Cost manufacturing

• Other German partners: - Siemens-Osram, Aixtron, Covion, HCStarck, Syntec, Novaled- FhG-IPMS, TU Dresden, Uni Kassel

• about 15 further partners from other European Universities

Page 20: Organic Light Emitting Diodes: Display and Lighting Technology of

• Achieve Smooth Transition from R&D to production: Close Collaboration of Fraunhofer Society and Industry

• Topics: OLED for Displays and LightingOrganic Solar CellsMemory and other Applications

• Tools: - Gen 2 Inline Pilot Production Tool (Displays&Lighting)- Reel-to-Reel R&D tool

• Location: New IPMS cleanroom: Virtually no building investment

A new Initiative: Center for Organic Materials and Electronic Devices Dresden (COMEDD)

Page 21: Organic Light Emitting Diodes: Display and Lighting Technology of

Outline of COMEDD

• Investment by FhG/state of saxony

• Operations organized in projects

• Projects are defined by advisory committee

• OLED foundry does pilot manufacturing

Projects Tools

Inline Reel-to-Reel Manufacturing Manufacturing

Center for Organic Materials and Electronic Devices Dresden (COMEDD)

Advisory BoardFunding agencies,

FhG, Industry

COMEDD Operations

Funding agencies:SaxonyBMBF, EC

OLED Foundry

Page 22: Organic Light Emitting Diodes: Display and Lighting Technology of

• OLED have still a long way to go, but

• Lifetime problem is close to being solved even for demanding applications

• Efficiency: OLED displays: will beat all other FPDs OLED lighting: should be able to surpass fluorescent tube

• COMEDD: New initiative to establish OLED manufacturing in Saxony

Conclusions

Page 23: Organic Light Emitting Diodes: Display and Lighting Technology of

Acknowledgment

• M. Pfeiffer, J. Blochwitz-Nimoth, G. He, G. Schwartz, K. Fehse, K. Walzer X. Zhou, J. Huang, A. Werner, A. Nollau, J. Drechsel, B. Männig, K. Harada, T. Fritz, B. Plönnigs, A. Beyer

• J. Amelung, W. Jeroch, C. May, M. Schreil, M. Toerker, U. Todt (FhG-IPMS)

• D. Alloway, P.A. Lee, N. Armstrong, Tucson (XPS/UPS)• N. Karl (Stuttgart)• D. Wöhrle (Bremen), J. Salbeck (Kassel), H. Hartmann (Merseburg)• C.J. Bloom, M. K. Elliott (CSU)

• BMBF, SMWA, SMWK, DFG, EC, FCI, NEDO