Overview of OLED Display Technology

Overview of OLED Display Technology

Homer Antoniadis, Ph.D. Product Development Group Manager phone: (408) 456-4004 cell: (408) 314-6460 email: [email protected]

Homer Antoniadis | OLED Product Development| page:1

Outline ! OLED device structure and operation ! OLED materials (polymers and small molecules) ! Evolution of OLED performance ! OLED process and fabrication technologies ! Color capabilities ! White emitting OLEDs ! Passive and active matrix driving schemes ! OLED market potential ! Products and demonstrators Homer Antoniadis | OLED Product Development| page:2

OLED Display and Pixel Structure Display

Pixel Cover glass

Cathode Emissive polymer layer

Cathode (Ba,Ca/Al 2000 Å) Emissive polymer layer ~ 800 Å

Conducting polymer layer

Conducting polymer layer ~ 1200 Å

Epoxy Anode

Anode (ITO 1500 Å)

Single pixel structure

Glass substrate

Human hair is 200X the thickness of the OLED layers Homer Antoniadis | OLED Product Development| page:3

OLED Device Operation Principles OLEDs rely on organic materials (polymers or small molecules) that give off light when tweaked with an electrical current

_ _ _ _ _ _ _ Emissive polymer _+ _+ _ _

! Electrons injected from cathode

Cathode

+

+

Conducting polymer

+

! Holes injected from anode ! Transport and radiative recombination of electron hole pairs at the emissive polymer

V

+ + + + ++ + + + Anode OLED device operation (energy diagram) Transparent substrate

light

Anode (ITO)

Conducting polymer

Emissive polymer -

-

LUMO

Cathodelayer (s)

e

e

LUMO

Light

HOMO h+

HOMO

h+ h+

ca. 100 nm Homer Antoniadis | OLED Product Development| page:4

10 - >100 nm

100 nm

Optoelectronic Device Characteristics Efficiency-Luminance-Voltage

Luminance-Current-Voltage 0

12

12

10

-2

10

-3

10

-4

10

-5

10

10

10

Efficiency (cd/A)

Efficiency (cd/A)

2

Current Density (A/cm )

-1

10

8 6 4

-6

10

8 6 4 2

-7

10

-8

-6

-4

-2

0

2

4

6

8

Voltage (Volts)

2 10

100

1000

2

Luminance (cd/m )

10000

0

0

2

5

4

Voltage (V)

10

LUMINANCE is the luminous intensity per unit area projected in a given direction

4

2

Luminance (cd/m )

10

3

10

The SI unit is the candela per square meter (cd/m2), which is still sometimes called a nit

2

10

1

10

The footlambert (fL) is also in common use: 1 fL = 3.426 cd/m2

0

10

-1

10

0

2

4

6

Voltage (Volts) Homer Antoniadis | OLED Product Development| page:5

8

http://www.resuba.com/wa3dsp/light/lumin.html

6

8

Evolution of LED Performance SM OLED

Polymer OLED

Courtesy of Agilent Technologies Homer Antoniadis | OLED Product Development| page:6

Electroluminescent Polymers

Conducting polymers ! Polyaniline (PANI:PSS)

NH

! Polyethylenedioxythiophene (PDOT:PSS)

PANI

PDOT

PSS

Emissive polymers ! Polyphenylenevinylene (R-PPV) ! Polyfluorene (PF) Processed by : Spin casting, Printing, Roll-to-roll web coating

IP owned by Cambridge Display Technology


R1

R1

R-PPV

n R1 R1

PF

n

Multiple emission colors achieved by Covion Different emission colors can be obtained with a variety of chemical structures

300 nm

PPP n

PPV OR

PT or CN-PPV


CN

S RO

500 nm

700 nm

Multiple emission colors achieved by Dow Chemical

R1 R 1

PF


n

Polymer OLED display fabrication steps

Deposit and pattern anode (ITO)

Pattern polymer layers (first conducting then emissive) Spin coating Ink Jet printing Screen printing Web coating

Vacuum deposit and pattern cathode (Ba,Ca/Al)


Ink Jet Printing to Pattern Polymers (Full Color Applications)

Ink Jet Head

Red emitter

Green emitter

Blue emitter

Substrate

Ink Jet printing to define and pattern R, G, B emitting subpixels


The Holy Grail: Flexible OLEDs

Sheila Kennedy, Harvard Univ., 1999 Homer Antoniadis | OLED Product Development| page:12

Electroluminescent Small Molecules

Hole transport small molecules ! Metal-phthalocyanines ! Arylamines, starburst amines

N

N

NPD

Emissive small molecules ! Metal chelates, distyrylbenzenes ! Fluorescent dyes

N O N

Al O

O

Processed and deposited by : thermal evaporation in vacuum

IP owned by Eastman Kodak


Alq3

N

Polymer and Small Molecule Device Structures

Small molecule

Polymer

Cathode - LiF/Al

Cathode – Ba, Ca/Al

ETL - Alq3 ETL - PPV, PF EML - doped Alq3 HTL - NPB

HIL - PDOT, Pani

HIL - CuPc Anode - ITO Substrate - glass

Anode - ITO Substrate - glass

Multi-layer structure made all in vacuum


Bilayer structure made from solution

Full color patterning with small molecules substrate

R emission layer

Cathode separator

Shadow mask

ITO

G emission layer

NPD

Alq3

Shadow mask

ITO

B emission layer

Shadow mask

ITO

Small molecules are thermally evaporated in vacuum


R, G, B pattering is defined by shadow masking in vacuum

White emitting small molecule OLEDs


Phosphorescent small molecule OLEDs

PHOLED technology offers significant room for further performance advances Homer Antoniadis | OLED Product Development| page:17

The Head-Start of Small Molecule OLEDs ! Manufacturing started ! ! ! ! !

Pioneer 1997 TDK (Alpine, 2001) Samsung-NEC Mobile Display (SNMD) (2002) RiTdisplay (2003) Sanyo-Kodak (2003)

! R, G, B colors available ! limited lifetimes for blue

! Shadow masking allows easy patterning for area color ! presents challenges with scalability and high volume manufacturing

! Shadow masking challenging for full color ! high throughput and scalability is a challenge


Advantages of Solution Processing (Polymer) OLEDs

! Lower fabrication cost ! fewer vacuum deposition steps - lower capital cost ! advantageous materials usage and scalability (I/J printing)

! Solution processing techniques ! compatible with printing techniques - lower cost for full color

! scalable to very large substrates (high volume manufacturing) ! better mechanical integrity ! compatible with roll process for flex manufacturing


Full-color/Multi-color Approaches RGB- polymer emitters

Color filters White emitter

Color Changing Media (CCMs)

Advantages: - power efficient - lower production cost - mature ITO technology

Advantages: - well-established technology (LCD) - no patterning of emitter necessary - homogeneous aging of emitter (?)

Advantages: homogeneous aging of emitter (?) more efficient than filters no patterning of emitter necessary

Disadvantages: - emitters have to be optimized separately (common cathode?) - differential aging of emitters - patterning of emitters necessary

Disadvantages: - power inefficient - ITO sputtering on filters - efficient white emitter necessary

Disadvantages: ITO Sputtering on CCMs stable blue emitter necessary aging of CCMs


EL Intensity (normalized)

Obtaining a Full Color OLED Display

Green polymer

1.0 0.8 0.6 0.4 0.2 0.0 400 450 500 550 600 650 700 750 Wavelength (nm)

AM TFT screen

Ink Jet printing of R,G,B emissive polymers defines the R,G,B subpixels

Red polymer

(xR, yR)

(xG, yG)

(xB, yB)

Blue polymer

R

G

B

Single pixel Homer Antoniadis | OLED Product Development| page:21

Passive Matrix Addressing

Output Current Output Current Output Current Output Current Output Current Output Current

• Line by line multiplex scanning • Duration of addressing is 1/mux rate • Pixel pulsed luminance = mux rate times average luminance • if 64 rows then pixel L=6400 nits for an average of 100 nits

• Limited addressed lines Homer Antoniadis | OLED Product Development| page:22

Courtesy of Philips Electronics

Passive Matrix Addressing

Output Current Output Current Output Current Output Current Output Current Output Current

• Line by line multiplex scanning

Courtesy of Philips Electronics

• Duration of addressing is 1/mux rate • Pixel pulsed luminance = mux rate times average luminance • if 64 rows then pixel L=6400 nits for an average of 100 nits

• Limited addressed lines Homer Antoniadis | OLED Product Development| page:23

Active Matrix Addressing

light

• Place a switching TFT at each pixel • Selected pixel stays on until next refresh cycle (pixels are switched and shine continuously) • Common cathode • Unlimited addressed lines


OLED Market will show strong growth Flat panel market 2006 $57B

Worldwide OLED Market, 2000-2006

Thsd. units

Value (Mio $) $3,500

250,000

value: iSuppli

value: DisplaySearch

units: iSupply

units: DisplaySearch

Other 3%

$3,000 200,000

PDP 12%

$2,500

TFT LCD 75%

150,000 $2,000

$1,500 100,000

OLED 4% PM LCD 6%

$1,000 50,000 $500

$0

0 2001

2002

2003

2004


2005

2006

2007

2008

Other: VFD: vacuum fluorescent display EL: electroluminescence DLP: Digital Light Processing source: iSupply/SRI 2002, Display Search 2002

Small Molecule Area Color Passive Matrix Displays

Motorola (by Appeal)

Samsung Electronics

Examples of Wireless Products With Kodak Display Technology

Lucky Goldstar (LG)


Small Molecule Full Color Passive Matrix Displays Caller ID Subdisplays

Samsung Electronics

Fujitsu F505i GPS

96x64 Full Color PM Display

With Pioneer Full Color (4,096 colors) PHOLED 1.1-inch 96x72 pixels display. Phosphorescent material developed by Universal Display Corp.

Kodak Licensed SNMD to Manufacture PM OLED Displays


Small Molecule Active Matrix Display Products

Eastman Kodak: Digital camera


Sanyo: Cell Phone with Digital camera

Kodak-Sanyo 15-in flat panel display (based on white)

15-inch HDTV format (1280x720) AM a-Si OLED display by Sanyo-Kodak Full Color based on white OLED with Integrated Color Filters. The two companies showed the prototype at the CEATEC JAPAN trade show (Sep 2002). Homer Antoniadis | OLED Product Development| page:29

Top Emitting Active Matrix OLED Display Top Emission Adaptive Current Drive technology, allows OLEDs to be larger and higher in brightness and resolution. A 13-inch full-color AMOLED using poly-Si TFT was made where the light emits through the transparent cathode and thus, the filling factor does not depend on the TFT structure. The schematic vertical structure of the device is substrate/TFT/metal anode/organic layers/transparent cathode/passivation layer/transparent sealing. Display format: 800x600 (SVGA); pixel pitch 0.33x0.33mm2


Polymer Passive Matrix Display Products

Philips: Electrical Shaver


Delta Electronics: Display for MP3 player

OSRAM Pictiva™ Evaluation Kit (www.pictiva.com)

San Jose, CA – May 15, 2003 -- Osram Opto Semiconductors, a global leader of solid-state lighting devices, today announced its Pictiva™ Evaluation Kit. Announced earlier this week, the Pictiva brand is Osram’s suite of organic light emitting diode (OLED) technologies. Pictiva displays offer a high level of brightness and contrast, video capabilities, wide viewing angles and a thin-profile, enabling developers and engineers to have greater design flexibility when developing the next-generation state-of-the-art electronics products. Homer Antoniadis | OLED Product Development| page:32