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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
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
Why are we interested in OLEDs?
AMOLED shipments to hit 185 million by 2014–
iSuppli reported by DigiTimes 8/19/2008
OLED Revenue will hit $5.5 billion revenue by 2015 with 37% CAGR (compared to 3% of total FPD) – DisplaySearch: 24/4/2009
AMOLED Revenue increased 110% in 2008 and will surpass PMOLED in 2009 to $350 million – DisplaySearch: 20/2/2009
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 developAMOLED displays
• Nokia sold >1 billion handset in 2008– needs >1 million/day!
Contrast Ratio & Luminance
Why OLED looks much brighter than LCD?
Because OLED has wider color gamut and superior contrast
2 – 2.9 cm (2010)Thinnest 3.7 cm (2008)Thickest 7.2 cmBLU:20 mm LCD module
1.9 cm (2009)Thinnest part: 2.88 cm Planned release: (NA)
3 mm (2007)
Big may be beautiful but thin is in– Display Daily October 12th, 2007
Sony’s flexible OLED is only 0.3 mm thick (2008)!
For environmental friendly & green displays
for future 3G and 4G wireless broadband communication interface
OLEDThe ultimate display
Keynote speech presented by
S. T. Kim, c.e.o. of Samsung SDIat IMID 2006, August 23, 2006
Daegu, Korea
Dream
OLED夢幻顯示器夢幻顯示器夢幻顯示器夢幻顯示器
Nokia N85 & N86 mobile phonesto 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 Device4.3-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
• 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
Marshall Electronics V-OL761 OLED Camera Top
-- 19/4/2009
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 pixelup to 50-in video/still bright images
OQO introduced new UMPC model w/5” OLED display – 8/1/2009
5" touchscreen OLED, 800x480 (WVGA)
Capacitance touchscreen is easier to fab on OLED than LCD
p-type materialn-type material
HOMO
LUMORGB
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!
Kido, SID 2008
SDI5” 800x480
186 ppi
SDI2.2” QCIF
135 ppi
Sony3.8” HVGA
150 ppi
SDI1.7’’
128x128
Sanyo-Kodak2.2” 521x218
165 ppi
Trend of developing high resolution OLEDs
130 140 150 160 200 ppi
Higher Resolution
Pioneer1.1”
141 ppi
350 ppi
SDI (Pentile)3.1” WVGA
800x480300 ppi
au Hitachi
SDI, 2”320x240, 200 ppi
Nokia
300 ppi
Samsung Anycall
SDI (Pentile)2.8” WVGA
800x480350 ppi
To achieve high aperture ratio in AMOLEDs
EML
Metal anode
Top Emission Structure
Larger aperture ratio
Metal Cathode
EML
Light
Conventional Structure
Smaller aperture ratio < 40%
Shorter lifetime
LightAlignment issue
TFT circuits
Advantage of OLED Micro-cavity
Reflection ElectrodeReflection ElectrodeReflection ElectrodeReflection Electrode
Organic layer
MicroMicroMicroMicro----cavity Structurecavity Structurecavity Structurecavity Structure
Reflection Electrode
Organic layer
Extraction of coherent Extraction of coherent Extraction of coherent Extraction of coherent light to forward direction light to forward direction light to forward direction light to forward direction
Increase in External Quantum EfficiencyIncrease in External Quantum Efficiency
Conventional StructureConventional StructureConventional StructureConventional Structure
400400400400 500500500500 600600600600 500500500500 600600600600 600600600600 700700700700
RGB SpectraRGB SpectraRGB SpectraRGB SpectraRGB SpectraRGB SpectraRGB SpectraRGB Spectra
Wavelength [nm]Wavelength [nm]Wavelength [nm]Wavelength [nm]
Brigh
tness
[a.
u.]
Brigh
tness
[a.
u.]
Brigh
tness
[a.
u.]
Brigh
tness
[a.
u.]
With μμμμ-C
Withoutμμμμ-C
1111....6666 timestimestimestimes 2222....5555 timestimestimestimes 2222....2222 timestimestimestimes
Transparent Electrode
Semi-transparent Electrode
To lower drive voltage and increase power effciency
“p-n” degenerate and transparent contacts
Tandem OLEDs – to increase cd/A/stability
Current Efficiency (cd/A):Single stack = L / Jn-Stacks ~ n (L / J)
Kido, SID Digest 2003Liao et al, Appl. Phys. Lett. 84, 167 (2004)
V3V
V V
L L LJ
V
LV J
V3V
V V
L L LJ
Principle of tandem OLED with CGL
+ + + + + + +_ _ _ _ _ _ _
Cathode side
Anode side
_+
_+
_
+
_
+
_
+
+
+
+
__+
_
+
_
+
_
+
_
+ __
+
_
+ _+
_+_
+_
_
+_
++
_ +_+
__+
+
_
+
Cathode side
Anode side
NPB+
V2O5- or FeCl 3
-
+
_
Emissionunit
NPBC545T:Alq 3
Cathode
ITOGlass
Alq 3
NPB
C545T:Alq 3
Alq 3
Emissionunit
Connecting layer
(Kido, 2003)BCP:Cs / V2O5/ NPB
(Tang, 2004)Alq3:Li / NPB : FeCl3
Connecting LayersConnecting Layers–– CGLCGLNot be too conductingNot be too conducting to avoid crossto avoid cross --talk (Kido SIDtalk (Kido SID ’’08)08)
350 400 450 500 550 600 650 700 750 800
0.00
0.02
0.04
0.06
0.08
0.10
0.12
0.14 1 unit 2 units
EL
inte
nsity
(au.
)
Wavelenght (nm)
2 units
528
528
Peak (nm)
0.28
0.33
CIEx
44
64
FWHM (nm)
0.6818.132.02
0.6311.011.01
CIEyVoltage
(V)yield
(cd/A)Units
@ 20mA/cm2
NPB (60nm)
C545T:Alq 3 (32.5nm)
Al-LiF
ITOGlass
CuPc (15nm)
Alq 3 (22.5nm)
NPB (60nm)
C545T:Alq 3 (32.5nm)
Alq 3 (32.5nm)
WO3 (10 nm)
Mg:Alq 3 (10nm)
1 unit
Al-LiF
ITOGlass
CuPc (15nm)
NPB (60nm)
C545T:Alq 3 (32.5nm)
Alq 3 (32.5nm)
Connecting Layer ofConnecting Layer ofNCTUNCTU
Ref: C.-C. Chang, S.-W. Hwang, H.-H. Chen, C. H. Chen, J.-F. Chen, Proceedings of IDW’04, 1285 (2004).
Sanyo-Kodak15” WXGA
Sanyo-Kodak5.5” QVGA
Sony 13” SVGA
SDI 15.1” XGA
TMD 17” XGA
Seiko Epson 40” WXGAIDT 20” WXGA Sony 24” XGA
Trend of developing large size AMOLEDs
Samsung21” 1920x1080
Sony 12.5” QVGA
5 15 20 40 inch
Larger size
LG20.1” 1280x800
Samsung 40” WXGASID 2005
Conventional AMOLED with LTPS TFT
BenQ-Siemens S88 Sony ‘CLIE PEG-VZ90’
WorseBetterUniformity
NMOS/PMOSOnly NMOSType
4 (730x920mm2)>7.5 (1950×2250mm2)Gen. Size
9 or 104 or 5Masks
HighLowMobility
LTPS TFTa-Si TFT
Advantages
� Mature technology in large display
� Better uniform brightness
� Low cost for large display
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
HTLEL
ETL
Anode
Substrate
Cathode
Issues of AMOLED on a-Si TFT
J. J. Lih, Info. Display, 20, 18 (2004)
Inverted OLEDa-Si TFT for AMOLED
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
J. K. Jeong, H. J. Chung, Y. G.. Mo, and H. D. Kim,Information Display, 24(9), 20 (2008)
Comparison of TFT technology for OLED
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在在在在Si基板與玻璃基板上基板與玻璃基板上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元件結構與電氣特性元件結構與電氣特性-- In:Ga:Zn = 1:1:1
K. Abe, H. Kumomi, K. Nomura, T. Kamiya, M. Hirano and H. Hosono, IDW’07, AMD9-2.
µµµµ > 12.9 cm2/V⋅⋅⋅⋅sVth 3.1 V
IOn/Off > 1010
µµµµ > 10.2 cm2/V⋅⋅⋅⋅sVth 3 V
IOn/Off > 108
Samsung a-IGZO TFT 元件架構與電氣特性元件架構與電氣特性元件架構與電氣特性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
– Luminance (cd/A) and Power (lm/W)
• Present–• 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/HKBUFunding by Innovation & Technology Commission of HK
K. W. Cheah Rick WongRaymond WongRicky Wong
Jason Cheng
Thank you for your attention
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