oled display training

- 1 -

OLED Display 1. Introduction

2. OLED & PLED materials

3. Device Operation

4. Device Performance

5. OLED Display- Full color OLED - PMOLED and AMOLED- Emission type- AMOLED products

6. Summary

1. Introduction Display

- 2 -

Electronic information displays

Projection Direct-view Off-screenDMDTMA

Light valveLCOS

Flat-panel

Shadowmask

Beamindex

Mono-chrome

Emitter

Nonemitter

Luminescence Incandescence

CL (Flat CRT)

Liquid-crystal Electro-chromic

Electro-phoretic

Ferro-electric

Activematrix

Passivematrix

Plasmaaddressed TFT MOS MIN Diodeothers TN STN FLC others

EL LED Gas discharge (PDP)

OrganicInorganic

Non-coherentdisplays

Coherentholograms

CRTCRT

FED VFD AC DC

Polymer Small Molecule

1. Introduction

- 3 -

Luminescence

Excitation Source

PL Photoluminescence PDP,

EL Electroluminescence Electric Field OLED, laser diode

CL Cathodeluminescence Cathode Ray(Electron) CRT, FED

i

V

p n

Inorganic Semiconductor LEDs(p-n junction LED)

1. Introduction What is OLED display?

- 4 -

Light

SubstrateAnode (ITO, IZO)

HIL / HTLEML

EIL / ETLCathode

OLED (Organic Light Emitting Diode):- , (Exciton) , .

1. Introduction History of OLED

- 5 -

LTPS-TFT 24.2 Full color OLED - 2003 Sony

LTPS-TFT 17 Full color OLED - 2002 TMD

LTPS-TFT 15.5 Full color OLED - 2003 SS SDI

a-Si TFT 20 Full color OLED - 2003 CMO LTPS-TFT 20.1 Full color OLED - 2004 LG.Philips LCD

a-Si TFT 21 Full color OLED - 2004 Samsunga-Si TFT 40 Full color OLED - 2005 Samsung

1. Introduction OLED

- 6 -

(Small molecule)

(Polymer)

(Fluorescence)

(Phosphorescence)

Bottom Emission

Top Emission

Color RGB LEDBlue EL + CCM

White EL + C/F

Passive Matrix

Active Matrix

1. Introduction AMOLED vs. TFT-LCD

- 7 -

AMOLEDAMOLEDTFT- LCDTFT- LCD

LC C/F

B/L

TFT

No backlight : Thinner & lighter

No LC : Fast Response time

Less cell process : Simple process

Wide viewing angle

High brightness

Better color purity

Easily applicable to flexible display

Polyimide

PolyimideLC

ITO CathodeOrganic ELTFTGlassPolarizer

Advantages of AMOLED

TFT

OLED/PolyLED

PolarizerGlassC/F + BM

Encapsulation

TFT

PolarizerGlass

Back Light

1. Introduction Market Forecast

- 8 -

2007 main display AMLCD 50.7% , OLED main display 5,300 , main display 10% .

Mobile Phone Sub Display()

0

200,000

400,000

600,000

MSTN 179,554 132,761 115,590 110,917 CSTN 160,027 170,368 128,770 100,852 AMLCD 153,524 194,789 239,895 272,791 OLED 2,266 10,990 41,120 53,495

2004 2005 2006 2007

Mobile Phone Main Display ()

(

x

1

0

0

0

)

050,000100,000150,000200,000

MSTN 50,251 47,442 22,282 17,059 CSTN 34,562 52,706 34,329 21,562 AMLCD 30,537 45,217 59,154 62,002 OLED 18,115 20,780 22,720 24,152

2004 2005 2006 2007

(

x

1

0

0

0

)

Source : DisplaySearch Q4 03 Quarterly mobile phone shipment and forecast report

1. Introduction Display Market

- 9 -

10 40

VGA

Size (Inch)

20 30

SVGA

XGA

UXGA

Digital HD TV

QVGA

SXGA

QXGA

D-Paper

IMT2000

PDA

Car Navi.

DesktopMonitorNote PC

Monitor

EWS

FPD PRT TV

TVMonitor

Resolution

50 60

CRT TV

Monitor Zone

TV ZoneMobile Zone

TFT

AMOLED

1. Introduction OLED Product Roadmap

- 10 -

1. Introduction OLED Product Roadmap

- 11 -

Display

Display

* OLEDs 2003 by UDC

1. Introduction OLED Display History

- 12 -

Sony 3.8

2004

LPL 20.1

SS 21

Epson 40 Tiled

1. Introduction Emission Mechanism

- 13 -

2. OLED & PLED Materials Small molecular OLED

- 14 -

Small molecular OLED

Formation of organic film and cathode metal9 Vacuum evaporation

2. OLED & PLED Materials Small molecular OLED

- 15 -

Optical absorption and photoluminescence

I-V characteristics of the ITO/TPD/Alq3/Al device

Absorption and PL emission spectra of Alq3

2. OLED & PLED Materials Polymer LED

- 16 -

Polymer LEDJ.H. Burroughes et al.

- Nature 347, 539 (1990)

Glass

ITO

External circuit

Al or Ca

PPV

Formation of organic film 9 Spin coating, Dip-coating, Ink-jet

Formation of cathode metal9Vacuum evaporation

2. OLED & PLED Materials Polymer LED

- 17 -

Optical absorption, PL and EL of PLED

I-V and L-V characteristics of the ITO/PPVPPV/Al device Absorption, PL and EL emission spectra of PPV

- 18 -

(, ) () ( Joule ) (;Tg ) ( , ) HOMO, LUMO

OLED

2. OLED & PLED Materials

Emissive materials : Small-molecular


- 19 -

Emissive materials : Dye


- 20 -

Phosphorescent sensitizer

Emissive materials : Polymer


- 21 -

Emissive materials : Polymer

Hole Transporting Materials

3. Device operation

- 22 -

(i) Quantum efficiency

(ii) Carrier injection and transport mechanism

(iii) Photonic effects

Internal quantum efficiency, int = rstq

is the ratio of number of excition formation events within device to number of electrons in external circuit

rst is fraction of excitions formed as singlets

q is efficiency of radiative decay of excitions

rst

q

ext

h+ - e- pair

SingletexcitonSingletSingletexcitonexciton

Triplet excitondirect deactivation

Triplet Triplet excitonexcitondirect deactivationdirect deactivation

EmissionEmissionEmission Thermaldeactivation

ThermalThermaldeactivationdeactivation

ExternalemissionExternalExternalemissionemission

Internaldissipation

InternalInternaldissipationdissipation

h+ e-

25% 75%

rst

q

ext

h+ - e- pair







Internaldissipation


h+ e-

h+ - e- pairh+ - e- pair







Internaldissipation


h+h+ e-e-

25% 75%

Basic processes :

(i) injection of electron and hole,

(ii) capture to form exciton,

(iii) emission

3. Device operation

- 23 -

3. Device operation

- 24 -

3. Device operation

- 25 -

Excited State

Triplet(75%)

OLED(25%) OLED(100%)

Singlet(25%)

Ground state

()( & )

Fast decay time(

3. Device operation

- 26 -




LUMO : Lowest Unoccupied Molecular Orbital HOMO : Highest Occupied Molecular Orbital

3. Device operation Injection of Charge

- 27 -

Injection dominated mechanisms : thermionic and tunneling emission

y Thermionic emission : J. Gmeiner et al., Acta Polym. 44, 201 (1993)

Thermionic emission

Tunneling emission

y Tunneling emission : J. Appl. Phys. 75, 1656 (1994)

I F2exp(-/F) = 8(2m*)1/23/2(3qh)-1/2

MetalPPV

J = A*T2exp(-b/kT)A* = 4qk2m*/h3

A*: Richardson constant, m* : effective mass

In MEH-PPV devices, F-N tunneling model applies at high fields and the barrier is determined by the metal work function and the energy levels of MEH-PPV (I.D. Parker, J. Appl. Phys. 75, 1656, (1994))

3. Device operation

- 28 -

Conduction in organic semiconductor : ohmic conduction and SCLC

y Ohmic conduction :

J = qn0V/d : P.W.M. Blom et al., Appl. Phys. Lett. 68, 3308 (1996)

y Space Charge Limited Current :JSCL = 9/8seV2/d3 : no traps

R.N. Marks et al., Synth. Met. 55, 4128 (1996)P.W.M. Blom et al., Appl. Phys. Lett, 68, 3308 (1996)

JSCL ~ V(m+1)/d(2m+1) : exponential distribution of traps (m=Tt/T)

P.E. Burrows et al., J. Appl. Phys. 79, 7991 (1996)

3. Device operation

- 29 -




y Fraction of internally generated light that emerges in forward direction is approx. 1/2n2 where n is the internal refractive index

External quantum efficiency, ext ~ 1/(2n2)

OLED

glass

Forward emission

4. OLED Performance

- 30 -

Current balance is set by the size of the barriers at the two electrodes. Lower voltage operation Higher efficiency Good thermal stability Longer life time

To improve device performanceTo improve device performance

Introduce HTL, ETL, HIL, EILIntroduce HTL, ETL, HIL, EIL i.e.) HeterostructureHTL : Hole transporting layerETL : Electron transporting layerHIL : Hole injecting layerEIL : Electron injecting layer

Balancing of electron and hole currentsBalancing of electron and hole currents

4. OLED Performance

- 31 -

Schematic diagram of the EL emission process in a typical multilayer OLED.

ITO

HIL

HTL

ETL

EIL

EML

Metal

Exciton

1000 ~ 1500

Cathode(low work function metal: Ca, Al:Li, Mg:Ag, etc)

Anode(Transperent electrode:ITO, IZO, etc)

4. OLED Performance

- 32 -

4. OLED Performance Lifetime

- 33 -

:

- ( ) : () ( 1/L0 , L0: )

- :

Log(T) = -a Log(I) + b (T: , I: (/), a: )


- 34 -


- 35 -

5. OLED Display

- 36 -

OLED

OLED with high efficiency

- Device structure

- Material(Phosphorescent OLED)

- Processing

- Outcoupling, full color

--

5. OLED Display What is pixel ?

- 37 -

Sub-pixel

Pixel

R G B

R G

BGR G B

RG

BR B

G

(a) Stripe (b) Delta Triad (c) Quad

Cf.) RGBW sub-pixel

5. OLED Display Color Mix

- 38 -

Color mix of sub-pixel

< 0.03 mixed color

15.0 XGA : 0.297mm x 0.099 (85.5 ppi)

17.0 SXGA : 0.264mm x 0.088 (96.2 ppi)

19.0 SXGA : 0.294mm x 0.098 (86.4 ppi)

20.1 UXGA : 0.255mm x 0.085 (99.6 ppi)

* ppi : pixel per inch

5. OLED Display Color Generation

- 39 -

Number of Color White balance Control# of Color = 2n (R) x 2n (G) x 2n (B)n: # of video data bits

Dynamic range of RGB data - current, voltage

RGB driving TFT size RGB emission time White OLED + color filter

3 bit= 8-gray/RGB = 512 colors 4 bit= 16-gray/RGB = 4,096 colors 6 bit= 64-gray/RGB = 262,144 colors 8 bit = 256-gray/RGB = 16,777,216 colors

%100

=

NTSCRGBDisplay

) LCD - Note PC : 45%~65%- Monitor : 65%~72%- LCD-TV : 72%

5. OLED Display Driving Method of FPD

- 40 -

CRT : E-beam scanning

FPD : Electrical signal scanning

0.1~1 msec

Brightness

time

Passive matrix Active matrix

Brightness Brightness

timetime

- 41 -

5. OLED Display

(b) Color Filter(CF)

(c) Color Change Media(CCM)

White OLED

Blue OLED

(a) RGB

RGB C/F CCM

RGB Patterning

RGB Patterning

ColorReproductionQuality

Approaches to Full Color OLED

EL & Color

Filter

EL&

Color Filter

5. OLED Display RGB OLED

- 42 -

Shadow mask () Pattern Metal Mask (Shadow Mask), Pixel

Issues

Fine Metal Mask

- Mask ( < 50, )- Mask - Mask (Mask )

- Mask Alignment ( Mask )

- Mask ( )

- Mask High Resolution- Mask Particle(/Metal) Device (Line , Dark Spot..)

Source

Substrate

Shadow Mask

Source

Substrate

10-7 Torr

Shadow Mask


- 43 -

Ink-Jet ITO Ink- Jet Printing Polymer Ink- Jet Print Process

ITOPassivation

TR Units

Glass Substrate

Bank Channel

Insulator

Conducting polymer (PFDT/PSS)

Bank

Red emitterRhodamine 101/PPV)

Ink-jetGreen emitter (PPV)

Blue emitter (Poly(dialkylfluorene))

Cathode


- 44 -

Laser Coating Donor Film Coating Pixel- : Evaporated onto the LITI Donor Film- : Blending onto the LITI Donor Film

Laser Induced Thermal Imaging (LITI)

Substratewith

Anode

HTL (Spin Coating)

Laser

Donor Film

LEPCoating

Cathode(Evaporation)

LITI PLEDDevice

Encapsulation

Nd:YAGLASER Beam

Substrate

Donor Film

LTHCLEP

adhesioncohesion

adhesion

LITI Process(R,G,B, 3 times)

LTHC : Light-To-Heat Conversion Layer, LEP : Light Emitting Polymer

5. OLED Display

- 45 -

Passive matrix

Digital driving method- Time ratio gray scale method - Area ratio gray scale method

Analog driving method- Simple pixel circuit(Two TFT + 1 Capacitor)- Compensation pixel circuit

Active matrix

OLED Displays

5. OLED Display PMOLED vs. AMOLED

- 46 -

Cathode

Organicfilm

AnodeGlasssubstrate

Glasssubstrate

TFT

Matrix EL device Line Emission

Passive Matrix (PM) Active Matrix (AM)

Matrix EL TFT Frame time Emission

1)

1) TFT : Thin Film Transistor

5. OLED Display PMOLED

- 47 -

Glass

ITO Inter Insulator

Organic layerCathode

Cathode separatorInter insulator

ITOGlass

AA

Cathode

Anode(ITO)

Glass

Scan1

Scan2

Scan3

Scann

Data1 Data2 Data3 Datam

A A

5. OLED Display PMOLED

- 48 -

PMOLED Scan Line, Data Line Pixel.

Scan 1

Scan 2

Scan 3

Scan 4

Data 1

Data 2

Data 3

Data 4

t1 t2 t3 t4 t5

Data 5

Data 6

Data

1 2 3 4 5 6

S

c

a

n

1

2

3

4

5. OLED Display PMOLED Layout

- 49 -

Metal

Metal/ITO

Inter-Insul. Cathode

Separator

Mask #4Mask #3

Mask #2Mask #1

5. OLED Display PMOLED Process

- 50 -

(1) Metal & ITO patterning (2) Inter-insulator

ITO glass Cleaning Metal(Mo, Cr) Sputtering

() Metal & ITO patterning : Mask #1 Metal patterning : Mask #2

Insulator layer formation : MASK #3(ITO edge breakdown )

- Photosensitive polymer


- 51 -

(3) Cathode Separator (4)

Pretreatment- Plasma treatment : ITO Work function - UV cleaning

(Shadow mask )

Cathode separator : Mask #4 ( pixel cathode line short )Reverse Taper angle ( Negative PR )


- 52 -

(5) (Cathode) (6) UV

Out Going Inspec.COF BondPol Lamin. Probe TestCell CutAging

COF Film


COF FilmCOF Film

(7) Aging, Scribing, Module

5. OLED Display PMOLED Grayscale

- 53 -

Grayscale methods

1datai 2datai 3datai tandai

Pulse-Amplitude modulation(PAM)- Current level control- Multiple Current sources- Matching problem

Pulse-Width Modulation(PWM)- ON/OFF timing control- Only One current source

CCV

5. OLED Display PMOLED vs. AMOLED

- 54 -

AMOLED PMOLED ( : Resolution => 640 x 480, Luminance =>100cd/m2)

100cd/m2

52500cd/m2

16.7ms32us

AM

~~~~ ~~ ~~

PM??

1 Frame Time : 16.7 ms( 60Hz )1 line scan time : 32 us( 525 line in 1 frame )Duty Driving = 100 x 16.7m / 32u 52500 cd/m2

5. OLED Display

- 55 -

0 5000 10000 15000 20000 25000 300007

8

9

10

11

12

Luminescence [cd/m2]

E

f

f

i

c

i

e

n

c

y

[

c

d

/

A

]

0

2

4

6

8

10

Voltage [V]

AM Operation PM Operation

PMOLED vs. AMOLED

5. OLED Display PMOLED Power dissipation

- 56 -

In a poly-LED display, there are three sources of power dissipation.

1. Light production:Plight = ILED VLED

2. Capacitive losses:Pcap = C Vswing Vsupply freq.

3. Resistive losses:Pres = I2 R

Power Dissipation in poly-LED Displays with Increasing Size and Resolution

Resolutioncolumn/row

80 60160 120320 240640 480

Diagonal(in.)1.22.45

10

Plight(mW)

15804002000

Pcap(mW)

1011013001800

Pres(mW)

1103008000

Ptotal(mW)

262002000

28000

Efficacy(lm/W)

5.32.81.10.3

(Pixel : 300300 um, luminance : 100 cd/m2, efficiency : 15 cd/A, green poly-LED)

5. OLED Display AMOLED

- 57 -

TFT-LCD TFT : switching

AMOLED TFTs : switching + current driving

Pixel array

LCCstStorage line

Gate line

Data line

Data

G

a

t

e

VDDGate line

Data line Pixel array

SW

DRV_TFT

Cst

OLED

GND

Data

G

a

t

e

TFT-LCD AMOLED

5. OLED Display AMOLED Process

- 58 -

INPUTINPUTTFT for AMTFT for AM

Evaporation

Seal Dispensing Canister CleanGetter Input


Encapsulation

Evaporation

Back End

Sealing

UV Expose

EvaporationMetal Source R/G/B Source

COF Film

Pre Treatment

INPUTINPUTTFT for AMTFT for AM

Evaporation

Seal Dispensing Canister CleanGetter Input


Encapsulation

Evaporation

Back EndBack End

Sealing

UV Expose

Sealing

UV Expose

EvaporationMetal Source R/G/B Source

COF FilmCOF Film

Pre Treatment


- 59 -

AMOLED Scan Line , Data Line Pixel ( Frame) .

t1 t2 t3 t4 t5

Data

1 2 3 4 5 6

S

c

a

n

1

2

3

4

Scan 1

Scan 2

Scan 3

Scan 4

Data 1

Data 2

Data 3

Data 4

Data 5

Data 6


- 60 -

TFT(Thin Film Transistor)Gate

Source Drain

G

S D

TFT : CdSe TFT, Organic TFT, a-Si TFT, Poly-Si TFT,

5. OLED Display Silicon

- 61 -

Semiconductor layer

Single Crystalline Silicon Polycrystalline Silicon amorphous Silicon

Grain boundaryGrain

Long range orderEg = 1.1 eVNo defect

CMOSHigh mobility=> ~ 600Low leakage

Long range orderEg = 1.1 eVGrain boundary

No long range orderLarge bandgapMany Trap states

CMOSMedium mobility=> ~ High off current

NMOS Low mobility=> 0.5 ~ 1High photo current

5. OLED Display a-Si:H

- 62 -

a-Si:H formation SiH4 + H2 amorphous Si deposition

Gas phase transport

Migration & chemical reaction

Surface desorption of byproduct(Exhaust)

Plasma

Deposition film

Substrate

Electron drift mobility 1 cm2/VsHole drift mobility 0.003 cm2/VsOptical band gap 1.5~1.8 eV300K conductivity 10-11/cm n+ a-Si conductivity 10-2/ /cmH content 10 at%

5. OLED Display a-Si:H TFT

- 63 -

a-Si:H TFT GATE DATA Bank /

/ (Deposition & Patterning Process) Photo Lithography

Patterning

(Cleaning)

SUBSTRATE

AlDC

AlAlAlAl

Ar+

Al

Ar+

TARGET

SPUTTER

R F

HSi SiNSi N

HSiHH

HN

NH H

HHH

PECVD

(Deposition)

PR (PR Coating)

(Exposure)

(Develop)

PR (PR Strip)

(Inspection)

(Wet Etch)

(Dry Etch)

FO Si

SiF4

SiPLASMA

Gas RF

(Etch)


- 64 -

a-Si:H TFT I-V Transfer curve Output curve


- 65 -

a-Si:H TFT Stability : SNU (SID 2005)

5. OLED Display Poly-Si TFT

- 66 -

Poly-Si formation Solid Phase Crystallization (SPC) base

Pure SPC

- High Temperature SPC

- Low Temperature SPC

Metal induced Crystallization ( MILC )

- Metal Induced Lateral Crystallization ( MILC )

- Continuous Grain Silicon (CGS)

- Field Enhanced Metal Induced Crystallization (FEMIC)

Alternating Magnetic Field Crystallization (AMFC)

Laser base Excimer Laser Annealing (ELA)

Sequential Lateral Solidication (SLS)

5. OLED Display LTPS TFT

- 67 -

Excimer laser crystallization Overlapped pulse scanning

ScanningDistanceper Pulse(Ls)

Laser BeamWidth(Lw)

L

a

s

e

r

B

e

a

m

L

e

n

g

t

h

OverlappingRate

= 100 X (Lw-Ls)/Lw

A

v

r

g

.

G

r

a

i

n

S

i

z

e

[

A

]

Laser Energy Density [mJ/cm2]E0 E0+10 E0+20

1000

2000

3000

4000

5000

6000

7000

8000

Non-Uniform GrainRegion

Overlap : 90% (10 Shot)Overlap : 92% (13 Shot)Overlap : 94% (17 Shot)Overlap : 96% (25 Shot)

E0+30 E0+40 E0+50 E0+60


- 68 -

1 Shot 5 Shots

10 Shots 20 Shots

Multiple shot effect Excimer laser crystallization


- 69 -

LTPS TFT Process Buffer SiO2 depo.a-Si:H depo.

Dehydrogenation

Laser annealing

Active patterning

Gate SiO2 depo.

Gate metal depo.

Gate patterning

Annealing

LDD doping

Interlayer SiO2Contact hole open

Passivation depo.

ITO Patterning

ITO depo.

S/D metal depo.

S/D Patterning

Passi hole open

Storage doping

n-type doping

p-type doping Bank Patterning

Bank layer depo.

n-type TFTp-type TFT

Buffer SiO2

Source

Passi-SiNx

INT-SiO2Drain

P-Si

Gate

Drain Source

ITO

P-Si

Bank layer

Gate

Storagecapacitor


- 70 -

I-V characteristics of LTPS TFTs

-20 -15 -10 -5 0 5 10 15 20 251E-15

1E-14

1E-13

1E-12

1E-11

1E-10

1E-9

1E-8

1E-7

1E-6

1E-5

1E-4

1E-3

0.01

D

r

a

i

n

C

u

r

r

e

n

t

(

A

)

Gate Voltage (V)

??? ??? ??? ?? ? ? ?? ??

??? ?? ???? ???????

Mobility : 68 cm2/V.secIoff : 0.16 pA/um

Mobility : 68 cm2/V.secIoff : 2.78 pA/um

Transfer curve


- 71 -

Uniformity of LTPS TFTsVth [V]

-2.5

-2.25

-2

-1.75

-1.5

-1.25

-11 4 7 10 13 16 19 22 25 28

Vth

Vth [V]

-2.5

-2.25

-2

-1.75

-1.5

-1.25

-11 4 7 10 13 16 19 22 25 28

Vth

ufl_m [cm2/Vs]

505560657075808590

1 4 7 10 13 16 19 22 25 28

ufl_m

ufl_m [cm2/Vs]

505560657075808590

1 3 5 7 9 11 13 15 17 19 21 23 25 27

ufl_m

5. OLED Display TFT Hysteresis

- 72 -

a-Si TFT Hysteresis : SNU (SID 2005)

5. OLED Display TFT Hysteresis

- 73 -

LTPS TFT Hysteresis : POSTECH & LPL (JJAP, 43, p. L482 (2004)

10 5 0 -5 -10 -151E-14

1E-13

1E-12

1E-11

1E-10

1E-9

1E-8

1E-7

1E-6

1E-5

1E-4

Vds = -0.1V

Vds = -10 V

Vth = 0.6 [V]

TFT W/L=8/20 [m/m] forward gate voltage sweep reverse gate voltage sweep

I

d

s

[

A

]

Vgs [V]


- 74 -

Two TFT and One capacitor pixel structure

Saturation region operation:

Device-to-device variation on panel

: Brightness uniformity on panel

Run-to-run variation

: Panel-to-to panel brightness uniformity

VDD IR drop problem

TFT hysteresis : Image Sticking

2)(2 thpSGpoxDSsat

OLED VVLWCII ==

data Line

Gate Line

SW_TFT DRV_TFT

Cst

OLED

GND

VDD

Ids

VDD

VOLED < Chess pattern >

VGS

Vds VTFT


- 75 -

Voltage distribution of VDD line : POSTECH & KIT (ITC 2005)

ColumnRow ColumnRow

V

D

D

[

V

]

ColumnRow ColumnRow

V

D

D

[

V

]

< Voltage distribution for full white >

RP

RPV

RHIPIXEL

VDD 1

VDDN

VDD2

IPIXEL

IPIXEL

IPIXEL

IPIXEL IPIXEL

RH

RH

RH

RH RH

RP

RPV

RPV

RP

< VDD structure >

A

A

B

B

Row Column

A

A

B

B

A

A

B

B

Row Column

V

D

D

[

V

]

150 300 450 60013

13.5

14

14.5

15

V

D

D

[

V

]

A-A'B-B'

< Voltage distribution for test chess pattern>


- 76 -

Voltage distribution of VDD line : POSTECH & KIT (ITC 2005)

R P

`

IPIXEL

RH

RV

RPV

VDD1

VDDN

VDD2

R P

R P

RPV

RPV

RPV

RPV

RPVRV

IPIXEL

IPIXEL

RH

RH

RH RHRVRV

RV

RHRH

IPIXEL

IPIXEL IPIXEL

R P

R P

R P

RV RV RV

RH

RVRVRV

VDDN

DDV1

DDV1

DDV2

DDV2

VDDM

DDV1

DDV2

VDDM

R P R P R P

R P R P R P

RPH RPH RPH

RPH RPH RPH

< VDD structure >

ColumnRow

V

D

D

[

V

]

ColumnRow

V

D

D

[

V

]

< Voltage distribution for full white >

Row Column

A

A

B

B

V

D

D

[

V

]

Row Column

A

A

A

A

B

B

B

B

V

D

D

[

V

]

150 300 450 60013

13.5

14

14.5

15

A-A'B-B'

< Voltage distribution for test chess pattern>


- 77 -

Poly-Si TFT AMOLED Non-uniformity of electrical characteristics in driving TFTs

Mobility, subthreshold swing, threshold voltage Luminance non-uniformity

a-Si TFT AMOLED Low cost, flexible displays

Well-established large manufacturing base for AMLCD displays

Poor mobility and reliability

Large-sized driving TFT

High operation voltage power consumption increase Stress-induced threshold voltage shift

Luminance non-uniformity & degradation

5. OLED Display AMOLED Driving Methods

- 78 -

Digital DrivingDigital Driving

Conventional Voltageprogrammed Compensation Circuit

Compensation Circuit

Analog DrivingAnalog Driving

AMOLED DrivingAMOLED Driving

TFT

TFT

TFT

*1) Area ratio gray scale method*2) Time ratio gray scale method

Hybrid Driving Feedback Driving

Voltage Programmed Current Programmed ARG*1 TRG*2

TFT

TFT

TFT

5. OLED Display Digital Driving Methods

- 79 -

Area ratio gray scale method (ARG)

2m gray scales can be acquired.

m=2, the areas of the sub-pixels are 1 : 2.

Four gray scales are acquired.


- 80 -

ARG & TRG

The frame time is divided into plural sub-frames.

2m n gray scales can be acquired.

m=n=2, the time of the sub-frames are 1 : 4.

16 gray scales are acquired.


- 81 -

Similar to PDP driving method. TU has no contribution to light emission. Cathode voltage variation required TLn have the ratio of 1:2:4:8:16:32 in length.

SF1 SF2 SF3TU1 TL1 TU3 TL3

OFF ON

SEL (SID 2000) : Display Period Separated (DPS) Driving

Gate 1

Gate 2

Gate NEL_cathode


- 82 -

SEL (SID 2000) : Simultaneously Erased Scan (SES) Driving

Good uniformity

Difficult to embody the driver system

Frame memory is needed.

The degradation of image quality is more serious than analog driving method


- 83 -

Hitachi (SID 2002) : Clamped Inverter Driving

SID 2003 SID 2004 SID 2004


- 84 -

Ryukoku (IDW 2004) : TRG + Current uniformization


- 85 -

SEL & Pioneer (SID 2004) - Resolve Luminance variation depending on ambient temperature &

degradation of OLED

5. OLED Display Voltage Programmed Driving Methods

- 86 -

2

223

222

21

21

21

)(/

)])([/

)_(/

__

_

dataDD

TthTthdataDD

TthTGSD

VVk

VVVVk

VVkI

==

=

If Vth_T3=Vth_T2

ResetStoring Data

VDD

C1

T2

T4

T3

T1Vdata

Select

OLED

GND

A

B

SNU (SID 2002)

Compensation : Vth (o), mobility (x), VDD (x) Mismatch problem between T2 and T3 Low contrast ratio Emission control S/W between OLED & T2 (IDW 2002)


- 87 -

Hanyang Univ. & SS SDI (Euro-display 2002)

( ) ( )2221

21

dataSGOLED VVDDKVKI

VI

===


- 88 -

SS SDI (SID 2003)

Hanyang Univ. (IMID 2003) VDDData Line

Select [n]

Select [n-1]

C1T1

T2

T4T3

em [n]

T5

em[n]

II IIIISelect [n-1]

Select [n]

Improve contrast ratio (C/R)


- 89 -

Sarnoff Corp. (IEDM 1998)

Vdata

1 2 3

( ) 2221

21

+==

+=

=


- 90 -

SS SDI & Hanyang Univ. (IDW 2003)

12

th_M1dataSG_M1 VV += VVDD

2

21

2121

)(

)V( I th_M1_ OLED

dataDD

MSG

VVK

VK

=

=

Compensation : Vth (o), mobility (x), VDD (x)


- 91 -

SS SDI & Hanyang Univ. (IDW 2003)

th_M1dataSG_M1 VV += VVDD

2

21

2121

)(

)V( I th_M1_ OLED

dataDD

MSG

VVK

VK

=

=

Compensation : Vth (o), mobility (x), VDD (x)


- 92 -

Hanyang Univ. & SS SDI (SID 2004)

th_T1DDdataCST VV-V +=V

+ -

1. Scan ON

2. Scan OFF

th_T1SUSdata

_SG_T1

VV-

V

+==

V

VV TGDD 1

2

21

2121

)(

)V( I th_T1_ OLED

SUSdata

TSG

VVK

VK

=

=

Compensation : Vth (o), mobility (x), VDD (o)

1TthDDdataSUS VVVV

V

_

CSTSUSG_T1 V-V

+==


- 93 -

KAIST (IDW 2001)

VD

VC

Data line

Select2 Select1

Select1

C1C2T1

T2

T3T4OLED

(1) (2) (3)

Select1

Select2

Data line

(1) Initialization, VG_T1 = GND(2) Compensation, VC1 = Vth_T1(3) Data input, VG_T1 = Vdata +Vth_T1

Vcomp

Compensation : Vth (o), mobility (x), Vc (X)


- 94 -

SSE (SID 2005)

TNO

+-

(1) Initialization, VC1=VDD (when, Vref = 0 V)(2) Compensation, VC1= VTO_OLED +Vth(3) Data input, VG_DTFT = Vdata +VTO_OLED +Vth

Compensation : Vth (o), mobility (x), GND (x) Low contrast ratio

5. OLED Display Current Programmed Driving Methods

- 95 -

Sarnoff Corp. (IEDM 1998) Toshiba (SID 2003)

Compensation : Vth (o), mobility (o), VDD (o) Difficult to display low gray level

2

21 )V( I th Data = SGVK

KIV DataSG 2+= thV

1. Programming Period 2. Driving Period

Data

SG

I

VK

== 2

21 )V( I th OLED


- 96 -

Sony (SID 2001) : Current mirror type,

Compensation : Vth (o), mobility (o), VDD (o) W/L of T4 is larger than that of T2

Reduce settling time Mismatch problem between T2 and T4


- 97 -

SNU (IDW 2002) : Current scaling type

Compensation : Vth (o), mobility (o), VDD (o) Current scaling type

Reduce settling time Mismatch problem between T3 and T4


- 98 -

Hanyang Univ. & SS SDI (IDW 2002)

Compensation : Vth (o), mobility (x), VDD (o) Capacitive coupling of C2

Solve settling problem


- 99 -

Michigan Univ & Kyushu Univ. (IEEE2001)

Waterloo Univ. (Eurodisplay. 2002)

5. OLED Display Feedback Driving Methods

- 100 -

Hanyang Univ. & SS SDI (SID 2005)


- 101 -

Waterloo Univ. & Ignis (SID 2005)


- 102 -

Philips SID 2002 SID 2004

5. OLED Display Hybrid Driving Methods

- 103 -

Hanyang Univ. (AMLCD 2005)

5. OLED Display Hybrid Driving Methods

- 104 -

Ignis (SID 2005)

5. OLED Display Emission Type

- 105 -

Bottom Emission OLED Top Emission OLED

Metal Anode

Semi-transparent Cathode

Transparent Plate

Light Buffer Layer

Emissive Layer

Al Wiring Light

Metal Cathode Transparent Anode

Emissive Layer

Pixel

- 106 -

Shift Register

Sampling Latch

Holding Latch

Voltage or Current DAC

Output Buffer

ReferenceVoltage or Current

Integrated data driving circuit Voltage mode

- Accurate output buffer

Current mode- Accurate current DAC Control nano-level current Devices non-uniformities

- Accurate current S/H circuit design- Accurate pre-charge circuit design- gamma correction

Data Driver IC

Data driver IC

5. OLED Display

HSYNCHCLK

RGB data

LOAD

Channel Outputs

5. OLED Display Integrated Data Driving circuits

- 107 -

SS SDI (IDW 2004) : External D-IC + analog sampling


- 108 -

SS SDI (SID 2005) : RGB adjustable gamma compensation

6-bit DAC : 3-bit decoder and voltage selector+ 3-bit decoder and resister ladder


- 109 -

SS SDI & Hanyang Univ. (IDW 2004) : External D-IC + DeMux


- 110 -

AU (IDW 2004)


- 111 -

AU (SID 2004)

5. OLED Display

- 112 -

NEC (IDW 2002)


- 113 -

NEC (Eurodisplay 2002)


- 114 -

AU (IDW 2003)

5. OLED Display AMOLED Product

- 115 -

Digital Still Camera ( Kodak Easyshare LS633, 2003. 5 ) 2.16 inch, 521 x 218 Dot pitch ; 0.084 x 0.151 mm2

Color arrangement : RGB delta Gate driver integration Analog sampling data driver integration

5. OLED Display PHOLED Product

- 116 -

Sub-Display of Mobile Phone ( Fujitsu F5005iGPS, 2004. 4)

1.1 inch, 96 x 72

Pioneer, PM-PHOLED

4,096 color

Phosphorescent developed by UDC

5. OLED Display AMOLED Product

- 117 -

PDA ( Sony Clie PEG-VZ90, 2004. 9 )

3.8 inch, 480 x 320 Top emission Contrast ratio : 1000: 1 Viewing angle : 180 Response time : 1 us

5. OLED Display AMOLED Development

- 118 -

SS SDI (SID 2005)- LTPS TFT - 2.6 480 x 640 (302ppi)- LITI (Laser-induced thermal imaging)- Top emission-200 cd/m2

LPL LGE (2004)- LTPS TFT - 20.1 1280 x 800- Small Molecule- > 1,000 cd/m2

SSE (2005)- a-Si TFT- 40 1280 x 800- White OLED + Color filter- 600 cd/m2

- Color Purity : 80%

6. Summary

- 119 -

OLED performance is rapidly improving Lifetime Efficiency & power consumption Color purity

Innovation is needed OLED performance & fabrication processes

Brightness uniformity

Global uniformity : IR drop of power lines

Local uniformity : Electrical characteristics of Driving TFT (Poly-Si TFT)

Reliability

OLED device : lifetime, thermal reliability

Driving TFT : degradation (a-Si:H TFT)

In the near future,OLED display will be widely used and the most attractive display of FPD.

oled display training

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