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