Recent Development of OLED Technology
Prof. C. H. (Fred) Chen
Centre for Advanced Luminescence Materials (CALM)
Hong Kong Baptist University
&
Display Institute
National Chiao Tung University, Taiwan
8/5/2009 at HK Green Display Technology Symposium
Outline
•
Introduction – The making of a Dream Display
•
Key OLED technology development
•
•
Graded device architecture – increase stability
•
Top emitting OLED with µ−cavity – enhance color
•
Tandem OLED – increase luminance efficiency/stability
•
p-i-n OLED – reduce drive voltage/increase power efficiency
•
IOLED – fab on a-Si TFT backplane for OLED TV
•
Oxide TFT backplane – new AMOLED
A look into the future
Why are we interested in OLEDs?
Worldwide displays value vs time in the market
Better than some of the best drug industries
OLED will have 50 years of continuing development and growth
OLED
AMOLED shipments to hit
185 million by 2014 –
iSuppli reported by DigiTimes 8/19/2008
AMOLED Revenue increased 110% in 2008 and
will surpass PMOLED in 2009 to $350 million
– DisplaySearch: 20/2/2009
OLED Revenue will hit $5.5 billion revenue by
2015 with 37% CAGR (compared to 3% of total
FPD)
– DisplaySearch: 24/4/2009
By Dr. S. J. Park
Future driver of a new display technology
Display Daily (8/14/2008)
• Nokia will only select panel suppliers who are able to develop
AMOLED displays
• Nokia sold >1 billion handset in 2008 – needs >1 million/day!
Why OLED looks much brighter than LCD?
Contrast Ratio &
Luminance
Because OLED has wider color gamut and superior contrast
Big may be beautiful but thin is in
– Display Daily October 12th, 2007
For environmental friendly & green displays
1.9 cm (2009)
Thinnest part: 2.88 cm
Planned release: (NA)
Thinnest 3.7 cm (2008) 2 – 2.9 cm (2010)
Thickest 7.2 cm
BLU:20 mm LCD module
Sony’s flexible OLED is only 0.3 mm thick (2008)!
3 mm (2007)
for future 3G and 4G wireless broadband communication interface
OLED
The ultimate
Dream display
Keynote speech presented
by
S. T. Kim, c.e.o. of Samsung SDI
at IMID 2006, August 23, 2006
Daegu, Korea
OLED夢幻顯示器
夢幻顯示器
Nokia N85 & N86 mobile phones to compete with
Apple iPhone 3G –
17/2/2009, Nokia OLED device
N85
• 2.6-in OLED
• 5 Mp camera
• Built-in GPS
• Wifi/HSDPA mobile connectivity
• $429 US
N86
• 2.6” OLED
•
•
•
•
Wireless TV
8 Mp DC
8 Gb storage
$375 Euro available Q2/2009
iRiver launches its new SPINN media player -- with a
3.3-in AMOLED made by Samsung, SDI, to compete
with iPod (29/8/2008)
www.t3.com/news
• 3.3-in QVGA OLED
• Touch screen
• 16 GB
• DMB TV
• DAB radio
• MPEG 4/WMA
• Blue tooth
• $179 US
Home Communication Device
4.3-in OLED with touch screen
Kodak introduced 7.6-in AMOLED
Wireless Picture Frame – 17/9/2008
AM-OLED panel made by Chi Mei EL
Marshall Electronics V-OL761 OLED Camera Top
-- 19/4/2009
• A wireless picture frame with a 7.6" AMOLED
• Made by CMEL, (16:9 aspect ratio, 800 x 480 resolution)
• White to black contrast ratio of 30,000:1
• $794 US Amazon.com
Samsung just introduced A877 Phone
w/largest OLED screen
-- 11/3/2009
• A QWERTY keyboard-slider
• 4-band GSM/EDGE/HSDPA
• 3 Mp camera
• 3.2 inch WQVGA OLED
• TouchWiz user interface
• GPS
• Full HTML browser
• $50 @Amazon.com w/plan
Samsung's new Projector-Phone –
www.popsci.com (26.1.2009)
• 0.7 inch thick
• 3.2 inch AMOLED (240 x 400 pixel)
• 5 Megapixel DSC and 3G wireless (to 7.2 Mbps)
• 10 lumen DPL projector to show 480 x 320 pixel
up to 50-in video/still bright images
OQO introduced new UMPC model
w/5” OLED display – 8/1/2009
Capacitance touchscreen is easier to fab on OLED than LCD
5" touchscreen OLED, 800x480 (WVGA)
The Art of Compartmentalization in Engineering –
Design & Optimization for each functional layer
(Kodak’s original patent) – circa 1985
But, there’ll be charge built-up in the interface!
RGB
LUMO
p-type material
n-type material
HOMO
Kido, SID 2008
Trend of developing high resolution OLEDs
Nokia
Hitachi
SDI (Pentile)
3.1” WVGA
800x480
300 ppi
Sanyo-Kodak
2.2” 521x218
165 ppi
SDI
1.7’’
128x128
Pioneer
1.1”
141 ppi
SDI
2.2” QCIF
135 ppi
130
au
140
SDI, 2”
320x240, 200 ppi
Samsung Anycall
Sony
3.8” HVGA
150 ppi
150
SDI
5” 800x480
186 ppi
160
SDI (Pentile)
2.8” WVGA
800x480
350 ppi
200 ppi
Higher Resolution
300 ppi
350 ppi
To achieve high aperture ratio in AMOLEDs
Larger aperture ratio
Alignment issue
Light
Metal Cathode
EML
EML
Metal anode
TFT circuits
Light
Conventional Structure
Smaller aperture ratio < 40%
Shorter lifetime
Top Emission Structure
Advantage of OLED Micro-cavity
Increase
Increase in
in External
External Quantum
Quantum Efficiency
Efficiency
Conventional Structure
Transparent
Electrode
Semitransparent
Electrode
MicroMicro-cavity Structure
Extraction of coherent
light to forward direction
Organic layer
Organic layer
Reflection Electrode
Reflection Electrode
RGB
RGB Spectra
Spectra
Brightness [a.u.]
１．６ times
２．５ times
２．２ times
With μ-C
Without
μ-C
４００
５００
６００
５００
６００
Wavelength [nm]
６００
７００
To lower drive voltage and increase power effciency
Tandem OLEDs – to increase cd/A/stability
V
V
L
V
3V
L
V
L
V
3V
L
Current Efficiency (cd/A):
Single stack = L / J
n-Stacks
~ n (L / J)
J
V
L
V
L
J
V
L
J
“p-n” degenerate and transparent contacts
Kido, SID Digest 2003
Liao et al, Appl. Phys. Lett. 84, 167 (2004)
Principle of tandem OLED with CGL
Connecting Layers – CGL
Not be too conducting to avoid cross-talk (Kido SID’08)
Cathode
Alq3
(Kido, 2003)
BCP:Cs / V2O5/ NPB
C545T:Alq3
Emission
unit
NPB
Connecting layer
Alq3
(Tang, 2004)
Alq3:Li / NPB : FeCl3
C545T:Alq3
NPB
ITO
Glass
Emission
unit
Cathode side
+
NPB+
_
V2O5- or FeCl3+
_
+
_
+ + +
_ _ _
+
+
_ _
Anode side
Cathode side
_ _+_+ _+
_ +
+
+
_ __+
_
_
++
_+
+
_ +
_ + _ +_
+_ _ _ +
+
+
_ + _ +_ +
_ _
+
+
+
_
_+
Anode side
Connecting Layer of NCTU
Al-LiF
0.14
C545T:Alq3
(32.5nm)
Al-LiF
NPB (60nm)
Alq3 (32.5nm)
WO3 (10 nm)
Mg:Alq3 (10nm)
Alq3 (22.5nm)
C545T:Alq3
(32.5nm)
NPB (60nm)
CuPc (15nm)
ITO
Glass
2 units
C545T:Alq3
(32.5nm)
NPB (60nm)
CuPc (15nm)
ITO
Glass
EL intensity (au.)
Alq3 (32.5nm)
1 unit
2 units
0.12
0.10
0.08
0.06
0.04
0.02
0.00
350 400 450 500 550 600 650 700 750 800
1 unit
Wavelenght (nm)
Units
yield
(cd/A)
Voltage
(V)
CIEx
CIEy
Peak
(nm)
FWHM
(nm)
1
11.0
11.0
0.33
0.63
528
64
2
32.0
18.1
0.28
0.68
528
44
@ 20mA/cm2
Ref: C.-C. Chang, S.-W. Hwang, H.-H. Chen, C. H. Chen, J.-F. Chen, Proceedings of IDW’04, 1285 (2004).
Trend of developing large size AMOLEDs
Sony 13” SVGA Sony 12.5” QVGA
IDT 20” WXGA
Sanyo-Kodak
5.5” QVGA
Sanyo-Kodak
15” WXGA
Sony 24” XGA
SDI 15.1” XGA
LG
20.1” 1280x800
15
Samsung
21” 1920x1080
Samsung 40” WXGA
TMD 17” XGA
5
Seiko Epson 40” WXGA
SID 2005
20
Larger size
40 inch
Conventional AMOLED with LTPS TFT
BenQ-Siemens S88
Sony ‘CLIE PEG-VZ90’
a-Si TFT
LTPS TFT
Mobility
Low
High
Type
Only NMOS
NMOS/PMOS
Masks
4 or 5
9 or 10
Gen. Size
>7.5 (1950×2250mm2) 4 (730x920mm2)
Uniformity
Better
Worse
Issues of AMOLED on a-Si TFT
a-Si TFT for AMOLED
Inverted OLED
Anode
Advantages
Mature technology in large display
Better uniform brightness
Low cost for large display
HTL
EL
ETL
Cathode
Substrate
Disadvantages
Only n-type a-Si TFT
Conventional OLED with bottom anode
can only be fabricated at the source end of
the driving a-Si TFT Poor stability
J. J. Lih, Info. Display, 20, 18 (2004)
LG reported ITOLED on a-Si TFT in SID 2008
To enhance NTSC color
LG to introduce 31-in OLED TV in 2010 – DigiTimes 4/2009
Comparison of TFT technology for OLED
J. K. Jeong, H. J. Chung, Y. G.. Mo, and H. D. Kim, Information Display, 24(9), 20 (2008)
Bonding characteristic of Oxide TFT vs Si
K. Nomura, H. Ohta, A. Takagi, T. Kamiya, M. Hirano, and H. Hosono, Nature, 432, 488 (2004)
a-IGZO在
在Si基板與玻璃基板上
基板與玻璃基板上TFT元件結構與電氣特性
元件結構與電氣特性
基板與玻璃基板上
-- In:Ga:Zn = 1:1:1
µ > 12.9 cm2/V⋅⋅s
Vth 3.1 V
IOn/Off > 1010
µ > 10.2 cm2/V⋅⋅s
Vth 3 V
IOn/Off > 108
K. Abe, H. Kumomi, K. Nomura, T. Kamiya, M. Hirano and H. Hosono, IDW’07, AMD9-2.
Samsung a-IGZO TFT 元件架構與電氣特性
J. K. Jeong, J. H. Jeong, H. W. Yang, J.-S. Park, Y.-G. Mo and H. D. Kim, Appl. Phys. Lett., 2007, 91, 113505.
12.1-in Oxide TFT-AMOLED panel –
Samsung SDI demo’d at SID 2008
The Past, Present & Future Trend
of
OLED Technology and Industry
•
Past –
•
Efficiency, Efficiency, Efficiency
–
•
Present –
•
•
Luminance (cd/A) and Power (lm/W)
Stability, Stability, Stability
Future – >2008
•
Cost down, Cost down, Cost down!
• Flexible OLED
• WOLED for lighting
Development of FOLED as “killer application”?
The future of white OLED lighting –
coming in 2010 - 2012
My colleagues at CALM/HKBU
Funding by Innovation & Technology Commission of HK
Thank you for your attention
Raymond Wong
K. W. Cheah
Jason Cheng
Rick Wong
Ricky Wong