OLED: the next-generation
display technology
Ching W. Tang
Institute for Advanced Study
Hong Kong University of Science and Technology
&
Department of Chemical Engineering
University of Rochester
Human Evolution…
From unknown artist
FPD Technology – past, present and future
•
•
•
•
•
•
•
Thin-film Electroluminescent Display
Field Emission Display
Plasma Display (PDP)
Liquid Crystal Display (LCD)
Organic Light Emitting Diode (OLED)
Electrophoretic Display
Others
LCD and OLED are both organic electronic devices
Evolution of LCD
Seiko Epson
Pocket TV
Blue LED
Nakamura/Nichia
Williams (RCA)
Electro-optic
effect
Schadt and
Helfrich
Twisted
nematic LC
1960
1970
40”
AMLCD/a-Si
Samsung
IPS LCD
Hitachi
OLED
1980
1990
a-Si-TFT
Active matrix
LCD (CdSe-TFT)
Brody/Fan
Westinghouse
Heilmeir (RCA)
LCD clock
AMLCD/a-Si
Matsushita
110” 4K TV
TCL, China
2000
2010
Today 50” LCD
TVs sell for as
little as US$500
Drastic price
reduction
AMLCD for
Laptops
LCD or OLED?
LCD
OLED
LED Back Light
v
ETL
HTL
Glass
Backlight Diffuser
Film
Backlight
Enhancement
Film
Rear Polarizer
Compensation
film
Glass
Substrate
Transparent
Electrode
Alignment
Layers
Transparent
Electrode
Glass
Substrate
Compensation
film
Front Polarizer
anti-scratch, anti-glare,
and
anti-reflection coatings
v
LC
Performance/Cost
LED
 Point light source
 III-V crystalline
semiconductors
 Used for backlighting
LCD TV screens
OLED
 Diffuse area light source
 Amorphous organic thin film
 Used directly as TV screens
AMOLED-TVs are getting larger and better…
LG's 77" curved UHD (4K) WRGB
2013
AMOLEDs are also used in head-mount micro-displays
Google Glass
Sony OLED HUD
eMagin’s AMOLED/Si
Himax CS- LCOS
AMOLED offers high resolution and
better optics
OLED displays are going flexible and wearable…
LG
Samsung
Some numbers:
Samsung
Wristband
Watch/Monitor
• Samsung shipped over
200 million Galaxy phones
as of 2/2014
• It also produces >90%
AMOLED panels
8.4” and 10.5” Samsung AMOLED Tablets – 2560x1600 resolutions
June/2014
LG 55”OLED-TV on the market Oct
2013
Hong Kong street price then was: US $10,000
US price now is as low as $4,000
Evolution of OLED
Electroluminescence studies in 1960’s
Electroluminescence studies in 1960’s
Helfrich and Schneider
PRL 14, 229 (1965)
Cathode
+
(K /anthracence-)
Anode
(aqueous KI +I2)
~104 V/cm
EL
~5 mm
~10-5 A/cm2
~2000V
Electroluminescence characteristics:
• Ohmic injection
Helfrich
Schadt
• Recombination near anode
Won 2012 Draper Prize for LCD Development
J. Dresner, RCA Review, 30, 223 (1969)
Recombination statistics
1/4
Na-K /
/ Se-Te
3/4
Appl. Phys. Lett. 48, 183 (1986)
Appl. Phys. Lett. 51, 913 (1987)
Appl. Phys. Lett. 51, 913 (1987)
Steve VanSlyke
Donor-Acceptor Heterojunction
Generation and Recombination at Organic / Organic Interface
Donor:
Holetransport
layer
Acceptor:
Electrontransport
layer
LUMOD
LUMOA
Hole current
Anode
Φe
Cathode
Electron current
Control injection barriers
and charge mobility:
HOMOD
Φh
~ 0.1µ
HOMOA
~ 0.1µ
Φe, Φh ~ 0.2 - 0.5 eV
µe, µh ~ 10-3 – 10-6 cm2/Vs
J. Appl. Phys. 65, 3610 (1989)
Tang, VanSlyke, Chen; Times cited: 3109
HTL (60nm)
ETL (60nm)
•
Mg:Ag
S
C540
N
•
•
Et
N
O
O
Et
CN
DCM1
°
°°
ITO
CH3
O
H3C
CH3
N
N
CH3
O
N
Al
O
HTL
CH3
N
CH3
CN
Alq
N
H3C
NC
NC
O
O
N
Host
N
Dopants
CH3
DCM2
Electrophosphorescence from Ir(ppy)3
Baldo et al, Appl. Phys. Lett. 75, 4 (1999) – Princeton & USC
Anode
Cathode
h+e
1/4
3/4
Singlet
exciton
Triplet
exciton
Ground state
Baldo
Forrest
Thompson
Watanabe et al. Proc. SPIE Vol. 4105, 175 (2001)
Pioneer Corp.
Lo = 280 cd/m2
Lo = 450 cd/m2
Blocking layer
J. Hwang et al. /Materials Science and Engineering R 64 (2009) 1–31
Multilayer OLED Energy Schemes
∆Εe > 0.3 eV
(Y. Cao)
e-
LUMO
Cathode
HIL
Anode
HTL
EML
ETL
EIL
EIL
HOMO
e-
LUMO
Cathode
h+
h+
∆Εh > 0.3 eV
HTL
Scheme I
EML
ETL
eHOMO
Anode
LUMO
h+
HIL
LG101
Son et al, USP 6720573, 2004
Scheme II
HOMO
Kim KK etal, APPLIED PHYSICS LETTERS 94, 063305 (2009)
Generic single-stack OLED device structure
Source LG Chem; http://www.lgchem.com/global/green-energy/oled-lighting
Tandem OLED device structures – improved efficacy and lifetime
Junji Kido
Kido, SID Digest 2003
Liao et al, Appl. Phys. Lett. 84, 167 (2004)
Ultra high-efficiency multi-photon emission blue phosphorescent OLEDs with EQE exceeding 40%
Sasabe/Kido et al, Organic Electronics 13 (2012) 2615–2619
Highlights:
• Highest EQE for blue Flrpic doped OLED
• Dual EML
• Dual ETL
• Tandem structures
MPE I
MPE II
I unit device
ηp (lumen/W)
43.2
23.5
28.0
EQE (%)
19.6
32.0
35.4
Drive (V)
3.4
9.0
8.7
Measured at 1000 cd/m2
OLED Life – from < 100 to >10,000 hours?
Materials Instability - A major technology hurdle
EQE ~ 1% p/e
~ 3 cd/A
Half-life ~100 h at 5 mA/cm2
Tang and VanSlyke, APL 51, 913 (1987)
TAPC
Improved stability with:
Hole transport layer: NPB
Hole Injection layer: CuPc
Half-life ~4000 h at 20 mA/cm2
32
Van Slyke, et al, Appl. Phys. Lett. 69, 2160 (1996)
Energetics of Arylamine Degradation
N
N
N
N
TAPC
NPB
 Bond dissociation energy of C-N and C-C (sp3-sp2) bonds
in NPB and TAPC ~3.3 eV (calc.)
 Lowest singlet excited state energies for TAPC and NPB
are ~ 3.3 eV and ~ 2.9 eV, respectively
33
Kondakov, J. Appl. Phys. 104, 084520 (2008)
Organic light-emitting diodes with a bipolar transport layer
Choong et al, APL 1999; time cited:45
Phosphorescent OLED Performance (From UDC, 2012 Data)
Power consumption
Samsung OLED-TV
Electricity cost:
$27 per year
@ 5 hour/day
Average wall plug power ~ 135 W
Average screen efficiency ~ 5 lumen/Watt
OLED Key Performance Features:
 Low-voltage emitter
 High efficiency / low power consumption
 RGB colors
 Fast switching time
 High contrast (black is black!)
 Wide-view angle
 Thin, light, flexible, scalable
Practically perfect for display applications!
Evolution of OLED Displays
OLED Pixel Architecture on Plastic Substrate
29 March 2012, SPIE Newsroom. DOI: 10.1117/2.1201203.004167
“A full-color, low-power, wearable display for mobile applications”
Huiqing Pang, Kamala Rajan, Jeff Silvernail, Prashant Mandlik, Ruiqing Ma, Mike Hack and Julie
Brown
First 20 Years(1980-2000) – Material and Device R&D Phase
Segmented OLED
Pope
Schneider
Williams
Dresner
1960-
2.4 inch dia
AMOLED
(EK/Sanyo)
Bi-layer structure
with hole
transport layer
Pioneer VIC
100 x 100
PMOLED
1987 APL
paper
Belljar Coater
64 x 32
PMOLED
5.5 inch dia AMOLED
(EK/Sanyo)
Pioneer car audio
1975
1980
1985
1990
Motorola
Cellphone
NPB HTL
Solar cell research
OLED discovery at EK
Doped
emitter
2000
1995
TDK
AMOLED
Polymer
Inkjet PLED
15”
OLED
Stilbenes
Optical
brighteners
AlQ
MgAg
OLED printhead
Integrated
shadow
mask for
PMOLED
Triplet emitters
Thompson/Forrest
13”
Fabrication of passive-matrix OLED displays (typically less than 200 lines)
OLED 2” 100x100 dots, Kodak 1990
Simple processes:
1. Pattern ITO anode
2. Deposit organic layers
3. Deposit and pattern cathode
But patterning cathode is disruptive!
Cathode rows patterned by
photolithography
OLED Passive Matrix Display Patterning Method
C.W. Tang, U.S. Patent 5,276,380 (1994)
Metal vapor
stream
Cathode
Pillar
Organic layers
ITO Anode
Cathode Isolation Gap
42
Integrated shadow mask - cathode separator
Nagayama, Miyaguchi, US Patent 5701055
Organics
/cathode
Pillar
Base
Glass
ITO
Cathode gap
43
Tiled Passive-Matrix OLED Displays
Geo-Cosmos (16’ diameter; 10,362 OLED panels)
Mitsubishi Electric / Pioneer Electronics
155” OLED TV, 3mm pitch
National Museum of Emerging Science and Innovation Tokyo, Japan
Early PMOLED Display Products
• Mobile phones
• Games
• Automobiles
• Portable electronics
Ted Tohma
45
First 20 Years(1980-2000) – Material and Device R&D Phase
Segmented OLED
Pope
Schneider
Williams
Dresner
1960-
2.4 inch dia
AMOLED
(EK/Sanyo)
Bi-layer structure
with hole
transport layer
Pioneer VIC
100 x 100
PMOLED
1987 APL
paper
Belljar Coater
64 x 32
PMOLED
5.5 inch dia AMOLED
(EK/Sanyo)
Pioneer car audio
1975
1980
1985
1990
Motorola
Cellphone
NPB HTL
Solar cell research
OLED discovery at EK
Doped
emitter
2000
1995
TDK
AMOLED
Polymer
Inkjet PLED
15”
OLED
Stilbenes
Optical
brighteners
AlQ
MgAg
OLED printhead
Integrated
shadow
mask for
PMOLED
Triplet emitters
Thompson/Forrest
13”
Display Addressing Methods:
Passive matrix
Active matrix
EL diode
Dawson et al/ SID 99 Digest, P438.
Without Vth
compensation
With Vth
compensation
Data Line
VDD
Select Line
Driving
Switching TFT
AZ
(auto-zero)
AZB
OLED
Id.sat ∝ µ(Vg-Vth)2
TFT
Dawson et al/ SID 99 Digest, P438.
Without Vth
compensation
With Vth
compensation
Data Line
VDD
Select Line
Driving
Switching TFT
King
Green
AZ
Stewart
(auto-zero)
Sturm
AZB
OLED
Id.sat ∝ µ(Vg-Vth)2
TFT
LCD Vs OLED (2000, Kodak)
G. Rajeswaren
Kodak LS633 (2003)
AMOLED Development Timeline - Courtesy of
Sanyo 5.5″
QVGA(2000.5)
Sony 13″ SVGA
(2001.5)(77ppi)
Toshiba 17″WXGA
(2002.5)(86ppi)
8.4” SVGA AMOLED
(May,2001)
ID tech
20” WXGA(73ppi)
15.1” XGA AMOLED
(Nov,2001)
Seiko-Epson(’04.4)
12.5”VGA(64ppi)
186ppi Top Emission
5.0” WVGA AMOLED
(May,2003)
Samsung SDI
LG 20.1” XGA
(75ppi)(’04.12)
SEC’05.1)
21”WUXGA(105ppi)
17” UXGA LITI
(May,2004)(118ppi)
15.5” WXGA AMOLED
(May,2003)
SEC’05.5)
40”WXGA(106ppi)
17” UXGA SGS
(Nov,2004)
§ 2000 AMOLED
Project Start
2000
2001
2002
2003
■
2004
3.6” LITI AMPLED 3.6” Ink-Jet AMPLED
3.6” QVGA
2.2” QVGA
(Oct.,2001)
AMOLED(Jan,2001)(May,2001)
CMOS 2.2” AMOLED Both-side Emissive
(Nov,2003)
(Jan.,2002)
2.2” AMOLED
2.2”
in
Phone
(Oct.,2002)
(CMOS, Dec,2002)
CDT/Seiko 2.8″
(100ppi)
Pioneer 3″
(150ppi)
SKD
(’03. 4)
HK Chung2.16”
On market
■
■
2.2” QCIF, QVGA
LITI(Nov,2003)
■
■
2.5” SOP
(Sep,2004)
■
2.65” VGA
(May,2005)
Samsung SDI
3.8” SONY
(’04 .9)
On market
AMOLED TVs by different paths
Samsung:
 LTPS TFT backplane
 Patterned RGB
LG:
 Metal oxide TFT backplane
 RGB by White OLED with CFA
55” OLED TV Exhibits in 2012 Consumer Electronic Show
OLED-TV pixel layout and emission spectra
Samsung
RGB
E. Kelley, Information Display 6/13, 2013
LG
W/RGB
Samsung Galaxy Note 3 Pixel Layout
Fine Shadow Mask
388 Pixels Per Inch (Pentile)
Laser close-space dye-transfer patterning method
Patent number: 5688551
Filing date: May 16, 1996
Issue date: Nov 18, 1997
Inventors: Jon Littman, Ching W Tang
Assignee: Eastman Kodak Company
Diode Laser
Donor sheet
vacuum gap
Receiver - Substrate
Sony 27” TV
2.4” 222 x 284 x 3 AMOLED
Panasonic all-printing UHD OLED TV (2013)
AMOLED: Color by White
W / RGB Format
W / RGBW Format
12.5 cd/A
2.6
6.6
12.5 cd/A
1.1
176 (W/RGB)
x 220
Ref: Van Slyke et al, ASID Display / IMID’04
2.6
6.6
1.1
12.5
132(W/RGBW)
x 220
W/RGB Vs W/RGBW Power Consumption
Power Consumption in mW
2.2”, 100cd/m2 white, 44% circular polarizer
400
W-RGB
300
200
W-RGBW
100
Average for 13,000 images:
180 mW - RGBW
340 mW - RGB
0
1
2
3
4
5
6
7
8
Image Number
Ref: Van Slyke et al, ASID Display / IMID’04
9
10 11
12 13
55” OLED-TV by LG (Oxide TFT; RGB filters/White OLED)
2012 Consumer Electronic Show
2001-2011
OLED Technology Development
ID Tech
20” aSi AMOLED
WXGA
Seiko-Epson
40”
AMPLED;
inkjet/tiled
2002
Samsung
Electronics 40"
aSi AMOLED,
WXGA, RGB/W
Koizumi Lighting &
Institute of Organic
Electronics, Yamagata
OLED Lamp
2005
Kodak EasyShare
LS633
2.2" AMOLED
OLED Products
Mitsubishi 155”
OLED TV, 3mm
pitch
Sony 27“ AMOLED
RGB by Laser
thermal printing
2010
Sony 11” XEL-1
AMOLED TV
eMagin
SVGA+
AMOLED
microdisplay
SMD
Flexible and
Transparent
AMOLED
LG 15”
EL9500
AMOLED TV
Sony CLIE PDA
3.8” AMOLED
AUO
2” AMOLED
SMD Ultra
Touch 2.8"
AMOLED
Microsoft
Zune 3.3”
AMOLED
Google
Nexus One
Cellphone
Osram
ORBEOS
OLED lamp
It took more than 30 years for OLED to emerge as a display technology!
OLED for Lighting Applications
Lumiotec OLED Lighting exhibit
DOE_SSL_2013_Multiyear Program Plan (Published 4/2013)
$/klm = 16.2
Efficacy = 84 l/W
49.3 / T. Kawata , SID 2013 DIGEST, p 685-8
Semiconductor Energy Laboratory
Samsung Forecast:
Source:Kiman Kim, Analysis Day 2013 Presentation, Samsung Display
Size Matters!
Yao Ming: 2.29 m
Gen 8
2.50 m
Gen 7
Gen 5
Gen 2
Gen 1
2.20 m
Gen 3
Linear source for vapor deposition of organic thin films – G5 size
OLED Challenges:
 Continuing Cost Reduction
 Lifetime Improvements (solving the blue
problem)
OLED will enable new display technology –
e.g. flexible displays
OLED will be THE next-generation display
technology – displacement of LCD is on-going
Evolution of OLED
Pope
Schneider
Williams
Dresner
Segmented OLED
Kodak EasyShare
LS633
2.2" AMOLED
2013 55”
TV
Samsung
LG
100 x 100
PMOLED
OLED
discovery
at EK
1960
Pioneer
PMOLED
Products
1970
1980
Tang/Vans
lyke
1987 APL
paper
2.4 inch dia
AMOLED
(EK/Sanyo)
1990
Polymer
OLED
SMD
Ultra
Touch
AUO
2” AMOLED
2000
Triplet
emitters
Thompson/
Forrest
TDK
AMOLED
2010
Sony 11”
XEL-1
AMOLED TV
OLED on
Plastic
It took more than 30 years for OLED to emerge as aSony
display
technology!
13”