Organic Light Emitting Diodes: Display and Lighting Technology of
Transcript of 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
Motivation: What is possible with OLED:
Samsung 40” TV display
Organic Semiconductors
Photovoltaic cellsOrganic materials Integrated circuits
• Large area & flexible substrates possible
• Large variety of materials
• Low cost
Small-Molecules
Organic semiconductors: Two variants
Polymers
Technology: Spin-On Technology: Evaporation
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:
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
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
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
• 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
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)
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
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
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
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
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
Institut für Angewandte PhotophysikTechnische Universität Dresden
LED performance vs. time
1965 1970 1975 1980 1985 1990 1995 2000 2005
0
20
40
60
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100
120
0
20
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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
OLED Lighting Applications
source: Philips Lighting March 2004 GE demonstrator
Signage General lighting
Technology Roadmap (USDC)(Diffuse lighting)
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
• 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)
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
• 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
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