advantages of oleds

1

Organic SemiconductorEE 4541.617A

2009. 1st Semester

2009 5 28

Changhee Lee, SNU, Korea

Changhee LeeSchool of Electrical Engineering and Computer Science

Seoul National Univ. [email protected]

2009. 5.28.


2009. 1st SemesterAdvantages of OLEDs

• Superior viewing performance:emissive bright colors, wide viewing angle, fast response time, and high contrast

• Simple fabrication processes: vacuum deposition, inkjet printing, spin coating,roll-to-roll (web) processing

Substrate

Vacuum Deposition

Ink-jetcartridge

Inkjet Printing

• Excellent operating characteristics:low operating voltage, power efficient, and wide temperature range

• Good form factor:Thin, light-weight, rugged, and flexible

Ultimate Portable Communication Devices

Fine Metal Shadow Mask

Source

Red ink Green ink Blue ink


http://www.universaldisplay.com/OLED vs LCD(http://www.oled-

display.net/oled-television) http://amoled.samsungsdi.com/

2


2009. 1st SemesterDevelopment of OLED technology

1998 1999 20001999 2001

2002 2003 2004 2005

PioneerS K d k

Pioneer, PM Sony SDI 15.1” Sanyo IDTech S

1982 1990 • • • 2006

Samsung SDIAMOLED 양산

2007

5.2” PM-OLED Sanyo-Kodak5.5” AM-OLED

4 Area ColorOLED

Sony13”

AMOLED

AM-OLEDXGA

LG, 8”-Full color

LGE1.8”PMOLED

MotoloraArea color

Toshiba 2.8”고분자 LED

TMD17” AM-PLED

XGA

Sanyo 14.7”AMOLEDWhite EL

5cd/A

IDTech20”a-Si

AMOLED

Sanyo-Kodak2.2” AMOLED

Samsung SDI

17” UXGA AMOLED

LGE-LPL20.1” XGAAMOLED

SEC40” WXGA

a-Si AMOLED

Samsung SDI2.6” AMOLED

Sony 3.8” PDATop-

1st OLEDITO/Diamine/Alq3/MgAg

USP 4,356,429

Ching W. TangEastman Kodak

Samsung SDI31” AMOLED

TV 개발

Sony

TMD (‘06)25” LTPS

AMOLED TV


ETRI 2” PM-OLED

UDCOLED

PioneerOLED

DNPOLED

Flexible OLED

Seiko-Epson40” WXGAAMOLED

(tiled, Ink-jet)

emissionAMOLED

1st Polymer LEDITO/PPV/Al

USP 5,247,190

Sir Richard Friend, FRSCambridge University

Sony11”

AMOLED TV(XEL-1) 판매

AMOLED TV

LGE (‘07)3.5” AMOLED

Oxide TFT


2009. 1st SemesterProgress in the efficiency of white OLEDs


N. Ide (Matsushita Electric Works, Ltd.), et al., SPIE (2008)

3


2009. 1st SemesterOrganic LEDs (polymers or small molecules)

Electron-transporting materialsN

ON

O N

OAl

Alq3

NNO(H3C)3C

PBD

Emitting materialsNC CN

ETL

Cathode

EML

－

Exciton

- LUMOETL

LUMOHTLElectron injection

-

LUMOEMLNN

Hole-transporting materials

N N

CH

H3C

TPD NPD

DPVBiAlq3

NO

NON

O AlN

O

NC CN

Ir(ppy)3

N

3

Ir

DCJTB

GlassITOHIL

HTL

+


++

+

-

-Φelight

Φmetal

HOMOETLHOMOHTL

ΦITO

Hole injection

++

-

HOMOEML

CH3 TPD α-NPD

Hole-injecting materials

PEDOT:PSS

n

S O3-

S O3-

S O3H S O3 H S O3H S O3H

SS

SS

SS

O O

OO

O O

OO OO

n

CuPC

CuN

NN

N N

N

NN

CH3

H3C

CH3

m-MTDATA


2009. 1st Semester

Kodak

B G Y RR=H, t-Bu

ADNKodakArAr

R

NO

O

NO

SiMe

Fluorescent emitters

DPVBiIdemitsu Kosan Alq3

Host

Almq3

TBPKodak

R=H Coumarin-545

Al N

ON

OAl N

ON

O

N

S

O ON

R

RR

SiMe

2PSPChisso


rubrenerubrene

Dopant

Mitsubishi

R1=R2=R3=R4=H, R5=MeDCM-2R1=R2=R3=R4=Me, R5=t-BuDCJTBKodakMe-QA

PioneerBCzBi

Idemitsu Kosan

R=H, Coumarin-545 PioneerR=CH3, Coumarin-545TKodak

N

N

DPAVBiIdemitsu Kosan

RR

4


2009. 1st Semester

Blue Green Red

DopantFI i

Ir(ppy)3

Ir(ppy)2acac

Btp2Ir(acac)NIr

O

2

ON

F

F

IrN

O O

2

NIr

N

O O

CF3F3C

2N N

NIr

O

2

O

S

NIr

3

N

H3C

Host and Phosphorescent Dopant Materials

Host

CN-PPV

CBP

mCP

UGH2 TAZ

PVK

FIrpic(CF3ppy)2Ir(pic) Ir(mpp)3

PtOEP

n

O

CN

CHCH2 nN

N N

NN

N

N N

N NPt

2

Si CH3H3C

NIr

2


Hole/ExcitonBlockingMaterials

BCP C60F42

mCP V

NNH3C CH3

FF

F

F

FF F

FFF F

FFF F

F F

FF

F

F

F

F

F FF

FF

F

F

FF

F

F

F

F

FF

FF

FF

Dr. H. N. Cho (InkTek)

NO

N

O AlO

BAlq


2009. 1st Semester

Fluorescence PhosphorescenceHost Alq3, ... CBP, TCTA, mCP, …

Excited state Singlet Triplet

Comparison of fluorescent and phosphorescent OLEDs

Excited state Singlet Triplet

Exciton diffusion length 50 ~ 100 Å > 1000 Å

Exciton blocking layer - BCP, Balq, etc.

Dopant concentration 0.1 ~ 3 % 5 – 15 %

Maximum quantum efficiency 25 % 100 %


Luminous efficacyRed: ~6 cd/AGreen: ~20 cd/ABlue: ~6 cd/A

Red: 6~20 cd/AGreen: 17~50 cd/ABlue: ~ 10 cd/A

Lifetime ~ 50,000 hour ~10,000 hour

5


2009. 1st Semester

Color CIE (x,y) Efficiency (cd/A) Half-Life (hr)

저

형

광

Red 0.65, 0.35 5.5 >80,000 @ 1000 cd/m2

Green 0.32, 0.62 19 40,000 @ 1000 cd/m2

Light blue 0.17, 0.30 12 21,000 @ 1000 cd/m2

Blue 0.15, 0.15 5.9 7,000 @ 1000 cd/m2

White 0 30 0 34 12 23 000 @ 1000 cd/m2

OLED Performance

저

분

자

White 0.30, 0.34 12 23,000 @ 1000 cd/m2

인

광

Red 0.65, 0.35 15 >22,000 @ 500 cd/m2

Orange 0.61, 0.38 22 15,000 @ 300 cd/m2

Green 0.31, 0.64 27 25,000 @ 600 cd/m2

Light blue 0.14, 0.23 8 -

White 0.39, 0.39 38 -

Red 0.68, 0.32 1.7 1790 @ 1000 cd/m2

Orange 0.58, 0.42 0.9 8138 @ 1000 nit


고

분

자

형

광

Yellow 0.50, 0.49 2.1 2420 @ 4000 cd/m2

Green 0.43, 0.55 7.7 2912 @ 2000 cd/m2

Blue 0.16, 0.22 6.9 >1147 @ 800 cd/m2

White 0.30, 0.33 3.8 235 @ 800 cd/m2

인

광

Red 0.67, 0.28 1.3 >8350 @ 100 cd/m2

Green 0.36, 0.59 22.8 2649 @ 400 cd/m2


2009. 1st Semester

• Electron-Hole Balance improved efficiency & Lifetime

ηφ = χγβφL

Electron-Hole Balance

1 0

balanced recombine all

Charge balance factor

ηφ χγβφLχ:coupling-out factor

γ:charge balance factor

β:probability of production of emissive species

φL:quantum efficiency of luminescence

To maximize the charge balance factor γ:

γ=1.0

γ=0.5


- Equal amount of electrons and holes are injected.- All the injected electrons and holes recombine.

Ambipolar emitting layerMixed emitting layer (co-doped host)p-type or n-type doping at the electrode interface

J. C. Scott et al., SPIE Proc., 3476, 111 (1998)

γ=0

hole only electron only

balanced escape all

6


2009. 1st Semester

Al

Al

Metal-doped organic layer(n-doping)

Control of:• Dopant concentration (Extent of reaction)

Electron injection layerEnhanced electron injection in OLEDs using an Al/LiF electrode

Al

p ( )• Thickness of doped layer

• Realize ohmic contact• Increase conductivity


J.Kido et al., Appl.Phys.Lett.(1998)L. S. Hung, C. W. Tang, and M. G. Mason, APL 70, 152, (1997)


2009. 1st Semester

ZnPC

Vacuum level

3.34 eV 5.28 eV5.24 eV 8.34 eV

E

LUMO

LUMO−e

Hole injection layer (p-doped organic layer)

F4TCNQ

FEFEHOMO

LUMO

HOMO

e

p-type doping

(a) (b)


(a) undoped (b) p-type doped M. Pfeiffer , K. Leo, X. Zhou, J.S. Huang, M. Hofmann, A. Werner, J. Blochwitz-Nimoth, Organic Electronics 4 (2003) 89–103

Weiying Gao and Antoine Kahn, Appl. Phys. Lett. 79, 4040 (2001)zinc phthalocyanine (ZnPc) doped with tetrafluorotetracyanoquinodimethane

7


2009. 1st Semester

Alq3(30 nm)

BCP:Cs(21 nm, 1:1)Al

N-type

Insulator

-

--

-

-

----

--

-+

+

+

+

+

++

++

+ BCP

Cs+

Alq3N

ON

O Al

p-i-n OLED

101

102

103

cm2 ) 104

105

L

ITOaNPD:F4TCNQ

aNPD(30 nm)

p-i-n structure

Insulator

P-type

++

+ ++

++ ++ +

+

++

--

-

---

-

---

α-NPD

F4TCNQ-

+-

Alq3 NON

NN

α-NPD

10-4

10-3

10-2

10-1

100

10

Cur

rent

Den

sity

(mA

/c

100

101

102

103

Luminance (cd/m

2)

Current Density Luminance


10-5

1086420

Voltage (V)

10-1

M. Pfeiffer , K. Leo, X. Zhou, J.S. Huang, M. Hofmann, A. Werner, J. Blochwitz-Nimoth, Organic Electronics 4 (2003) 89–103


2009. 1st Semester

US 20080030131 (2008.02.07) Francisco J. Duarte, Kathleen M. Vaeth, Liang-Sheng Liao, Eastman Kodak CompanyA light-emitting device, comprising: a multi-layer stack of materials supported on an optically transparent support member, a first spatial filter, and a second spatial filter spaced from the first spatial filter. The multi-layer stack including at least one organic light-emitting layers, an anode layer, and a cathode layer. The first spatial filter is disposed intermediate the multi-layer stack of materials and the second spatial filter.

Tandem OLED

2 2

33

OLED 2 Unit

P-N junction

CBP:Ir(ppy)3 dopedOLED 3 OLED 3 Unit

cathodeMg:Ag

CBP:Ir(ppy)3 dopedOLED 2

aNPD:FeCl3(48nm, 1 %)

Alq3:Li(24nm, 1.2%)


1

1

Glass

ITO

P-N junction

anode

OLED 1 Unit

aNPD:FeCl3(48nm, 1 %)

Alq3:Li(24nm, 1.2%)

CBP:Ir(ppy)3 dopedOLED 1

3배의 빛L. S. Liao, K. P. Klubek, and C. W. Tang, Appl. Phys. Lett. 84, 167 (2004)

8


2009. 1st SemesterI-V characteristics of organic semiconductors

Injection limited

Thermionic emission

]1)[exp( −=Tk

eVJJB

s )exp(2*

TkeTAJB

bns

φ−=

Current

Bulk Limited

Ohmic (Doped semiconductor)

EepJ μ=

Tunneling

)exp(2

EbEJ −

≈qh

qmb3

)(28 2/3* φπ=


SCLC (undoped semicond. or Insulator)

3

2

89

dVJ roSCLC μεε=


2009. 1st Semester

2.9 eV

Al

4.3 eVITO

O

O

MEH PPV

Thermionic Emission into low mobility organic semiconductor

EF4.8 eV

5.3 eVMEH-PPV


P. S. Davids, I. H. Campbell, and D. L. Smith, J. Appl. Phys. 82, 6319 (1997).

9


2009. 1st Semester

(a) (b)

Tunneling mechanism

(c) (d)


I. D. Parker, J. Appl. Phys. 75, 1656 (1994).


2009. 1st Semester

0<V<VΩ

+

Organic Semiconductor

electrodeelectrode + +

++++

d

Space-charge-limited (SCL) current

ITO Au

OC1C10-PPV

+

dt ττ >(a) (Ohmic current)

VΩ<V

electrode+

+++

Organic Semiconductor

29 V

0.3 μm

d=0.13 μm

0.7 μm


electrode++ ++++++ +

dt ττ <(b) (SCL current)

++

t.predominan is conduction SCLC ,At t.predominan is conduction ohmic ,At

dt

dt

ττττ

<>

389

dVJ roSCLC μεε=

P. W. M. Blom M. J. M. de Jong, and J. J. M. Vleggaar, Appl. Phys. Lett. 68, 3308 (1996).

10


2009. 1st SemesterField-dependent mobility in SCL current

])(891.0exp[89 2/1

3

2

dV

TkdVJ PF

BroSCLC βμεε=

P. N. Murgatroyd, J. Phys. D: Appl. Phys. 3, 151 (1970).

OC1C10-PPV


P. W. M. Blom, M. J. M. de Jong, and M. G. van Munster, Phys. Rev. B 55, R656 (1997).

ITO Au+


2009. 1st SemesterSpace-charge-limited (SCL) current

ITO Au

OC1C10-PPV

+


Poly(dialkoxy-p-phenylene vinylene) (OC1C10-PPV)P. W. M. Blom M. J. M. de Jong, and J. J. M. Vleggaar, Appl. Phys. Lett. 68, 3308 (1996).

11


2009. 1st Semester

. ,

SCLC limited-Trap

12

1

TTm

dVNNJ t

m

mm

tv =∝ +

+−μ

318

eV 15.0≈tE

SCL current with an exponential trap distribution

3-18 cm10≈tN

Changhee Lee, SNU, KoreaP. E. Burrows, Z. Shen, V. Bulovic, D. M. McCarty, S. R. Forrest, J. A. Cronin and M. E. Thompson, J. Appl. Phys. 79, 7991 (1996).


2009. 1st SemesterInterface-limited injection model


M. A. Baldo and S. R. Forrest, Phys. Rev. B 64, 085201 (2001)

12


2009. 1st SemesterCarrier Recombination

Recombination of electron hole pairs Singlet exciton S=0

↑↑=21χχ

Triplet exciton S=1

Spin-allowed transitionfast efficient Spin-forbidden transition

)(2

121 ↓↑−↑↓=χχ )(

21

21 ↓↑+↑↓=χχ

↓↓=21χχ


M. Segel, M. A. Baldo, R. J. Holmes, S. R. Forrest, Z. G. Soos, Phys. Rev. B 68, 075211 (2003)

Singlet exciton S=0

fast, efficientFluorescence

Triplet exciton S=1

slow, inefficientPhosphorescence


2009. 1st SemesterExciton Recombination Zone

- Electron-

e-h Recombination Zone ~ 10 nm


+

Φmeta

l

ΦITOhole

EML ETL+

C. Adachi, T. Tsutsui, and S. Saito, Optoelectron. Devices Technol. 6, 25 (1991).

13


2009. 1st Semester

TPD(65 nm) Alq3

(50 nm)

2.5 eV3 eV

N N

CH3

H3C

TPD Alq3

NO

NON

O Al

(a) (c)

Electron-hole and electric field distribution

5.4 eV5.7 eV

(b) (d)


B. Ruhstaller, S. A. Carter, S. Barth, H. Riel, W. Riess, and J. C. Scott, J. Appl. Phys. 89, 4575 (2001).


2009. 1st SemesterQuantum efficiency roll-off at high current

(2002) 1465 80, Lett. Phys. Appl. Kafafi, H. Z.and Kalinowski J. Stampor, W.i,Szmytkowsk J.

-fieldE11 X ,X T ,S

:excitons ofon dissociati field Electric +− ⎯⎯ →⎯

∗


(2002) 874 80, Lett. Phys. Appl. Marchetti, P. Alfred and Tang, W.Ching Young, H.Ralph

0Xor X

11 S T ,S

:quenchingexciton -Polaron -

⎯⎯⎯ →⎯

∗+

14


2009. 1st SemesterQuantum Efficiency vs Current of phosphorescent OLEDs

Triplet – Triplet (T – T) Annihilation

⎥⎦

⎤⎢⎣

⎡++−=⎥

⎦

⎤⎢⎣

⎡++−=

T

T

TT JJ

JJ

JJ

Jkqd 811

4811

2 20 τη

η

Changhee Lee, SNU, KoreaRef. M. A. Baldo, C. Adachi, and S. R. Forrest, Phys. Rev. B 62, 10967 (2000)


2009. 1st Semester

0=dt

dnT 021 2 =−+

gdJnnk T

TT τ

(근의 공식)

⎤⎡⎤⎡++− T

JJkqdJk

81212)1(1

22

τττ 2k

T – T Annihilation: Steady-state solution

⎥⎦

⎤⎢⎣

⎡++−=

⎥⎥⎦

⎤

⎢⎢⎣

⎡++−==

TT

T

TTT J

Jkqd

Jkkk

qdn 81112111

ττ

τττ

)4

( 12

−= TT Jqd

k τQ

τTnL = QE :

τη

Jn

JL T==

nL

T1

0η : 0=Tk 인 경우, 즉 , T-T annihilation이 없는 경우이므로 gdJnT =

τ

Light emission intensity


qdJJL 1

0 ===∴ τη

⎥⎦

⎤⎢⎣

⎡++−=⎥

⎦

⎤⎢⎣

⎡++−=

T

T

TT JJ

JJ

JJ

Jkqd 811

48112

0 τηη

M. A. Baldo, C. Adachi, and S. R. Forrest, Phys. Rev. B 62,10967 (2000)

15


2009. 1st SemesterTriplet exciton – polaron quenching


S. Reineke, K. Walzer, and K. Leo, Phys. Rev. B 75, 125328 (2007)


2009. 1st Semester

11212 Pρρρτ 2212 Pρρτ 112 Pρτ 22 PτP2P1

고 반사전극

투명전극

유기 박막

Spontaneous emission from planar microcavity

L

-z z’=L-z0

1ρ 22 , τρ cL2


)2()2()()( 2121

1222 cLtWP

cztWPtWPtEL −+−+= ρρτρττ

)22( 12112 c

LcztWP −−+ ρρρτ

D. G. Deppe, C. Lei, C. C. Lin, and D. L. Huffaker, J. Modern Optics 41, 325 (1994)

16


2009. 1st SemesterSpontaneous emission from planar microcavity

∫∫∞

∞−

∞

∞−−+= dtti

cztWPdttitWPEL )exp()2(

2)exp()(

2)( 1122

2 ωπρτω

πτω

dtticLtWP∫

∞

∞−−+ )exp()2(

2212 ω

πρρτ

)(ωWP

....)exp()22(2

12112 +−−+ ∫∞

∞−dtti

cL

cztWP ω

πρρρτ

...1)[(

......)()(

)()()()(

22

121

2

12

4

21212

22

1212

2

212

2

1222

11

1

1

+++=

+++

++=

+

+

cLi

czi

czi

cLi

cLi

czi

cLi

czi

L

eeWP

WPeWPe

WPeWPeWPE

ωωω

ωωω

ωω

ρρρρωτ

ωρρρρτωρρρτ

ωρρτωρτωτω


] ... 4

2121

2

21

12112

+++ cLi

cLi

eeωω

ρρρρρρ

}] ...1{

...}1{1)[()(2

21

2

21

2

12

2

122

1

+++

+++=

cLi

cLi

cLi

czi

L

ee

eeWPEωω

ωω

ρρρρ

ρρρωτω

cLi

cLi

ee ω

ω

ρρρρ 2

12

2

12

1

1...1−

=++


2009. 1st SemesterSpontaneous emission from planar microcavity

cLi

czi

L

e

eWPE ω

ω

ρρ

ρωτω 2

21

2

122

1

1)()(1

−

+=

2

2121

11122

2

4

)()2cos(21

)]2cos(21)[1()(

π

ωω

ω

ω

nz

WP

cLRRRR

cnzRRR

E L

−+

++−=

Emission spectrum in the forward direction

Interference effect

Fabry-Perot Resonator


2

2121

1112

)()4cos(21

)]4cos(21)[1( ω

λπ

λπ

WPnLRRRR

nzRRR

−+

++−=

22

222

212

1 1||,||,|| RRR −=== τρρD. G. Deppe, C. Lei, C. C. Lin, and D. L. Huffaker, J. Modern Optics 41, 325 (1994)

17


2009. 1st Semester

ρ2

θ

θSemitransparent cathode

Radiation mode in top-emitting OLED

Lz ρ1

o

Emitting layer

Reflective anode

)cos4exp(12

),( θπ ops nzir+

Changhee Lee, SNU, Korea32

C. Qiu, H. Peng, H. Chen, Z. Xie, M. Wong, and H. S. Kwok, IEEE Trans. on Electron Dev. 51, 1207 (2004).

)()cos4exp(1

)exp(1),( ),(

int),(

22),(

2),(

1

),(1

),( λ

λθπ

λλθ psps

opsps

op

psext IT

nLirr

irI

−

+=


2009. 1st SemesterResonant emission from microcavity


A. Dodabalapur, L. J. Rothberg, R. H. Jordan, T. M. Miller, R. E. Slusher, and J. M. Phillips, J. Appl. Phys. 80, 6954 (1996).

Blue Green Red

18


2009. 1st SemesterRadiation mode in top-emitting OLED

Conventional OLED

Top-emission OLEDConventionalTop-emission

LambertianSimulation (TE)

C ti l OLEDT i i OLED

Simulation (TE)

ConventionalTop-emission


C. Qiu, H. Peng, H. Chen, Z. Xie, M. Wong, and H. S. Kwok, IEEE Trans. on Electron Dev. 51, 1207 (2004).

Conventional OLEDTop-emission OLED


2009. 1st Semester

% 51~ :)(sin 21 θθ ≤=−

corganic

substrate

nn

External quantum efficiency of OLED

%.~n

ηn

norg

Corganic

airc 517

21 :)(sin 2

11 ≈=≤ −θθ

organic

% 31.5~ :21 cc θθθ ≤≤θ

Metal/Alq3 (x)/PVK (40 nm)/ITO (150 nm)Metal/Alq3 (80 nm)/PVK (40 nm)/ITO (x)

G. Gu, DZ Garbuzov, PE Burrows, S. Venkatesh, SR Forrest, ME Thompson, Opt. Lett. 22, 396 (1997)


(b)A. Chutinan, K. Ishihara, T. Asano, M. Fujita, S. Noda, Org. Electron. 6, 3 (2005).

19


2009. 1st Semester

Standard OLED structure OLED with aerogel interlayer OLED with integrated DFB grating

Methods of improving out-coupling efficiency

221

orgC nη ≈

OLED with scattering microspheres OLED with microlenses OLED built atop a mesa structure


K. Meerholz and D. C. Müller, Adv. Funct. Mater. 11, 251 (2001).


2009. 1st Semester

Doubling Coupling-Out Efficiency in Organic Light-Emitting Devices Using a Thin Silica Aerogel LayerT. Tsutsui, M. Yahiro, H. Yokogawa, K. Kawano, M. Yokoyama, Adv. Mater. 13, 1149-1152 (2001).

Index matching using a thin aerogel layer


20


2009. 1st SemesterPhotonic crystal


Yong-Jae Lee, Se-Heon Kim, Joon Huh, Guk-Hyun Kim, and Yong-Hee Lee, Sang-Hwan Cho, Yoon-Chang Kim, and Young Rag Do, Appl. Phys. Lett. 82, 3779 (2003).


2009. 1st SemesterDegradation Processes

Cathode

Cathode- Delamination of metal (Peel-off)- Corrosion & oxidation; O2, H2O

• Encapsulation- Permeation of H2O and O2, etc.• Ambient environment:- Temperature, moisture, and UV light, etc.• Joule heating, etc.

H2O, O2

ETL

HIL

HTL

EML

EIL－

Exciton

- Diffusion of metals such as Ca, Al, etc.

Electrode Interfaces- Interfacial degradation

Changes in injection efficiency- Formation of oxide layer: injection barrier- Electrochemical reaction with organic layers- Degradation of PEDOT:PSS- Degradation of p-, n-doped layers, etc.

Organic layers- Degradation of organic materials- Photo-oxidation

두께

: 100

~200

nm


Substrate(Glass, plastics, etc.)

ITO

HIL+

Anode- ITO inhomogeneity: injection barrier- Oxygen or In diffusion Degradation of organic layers- Dust, particles, etc.

- Morphological changes (Crystallization): change of mobility, trap distribution

change in e-h balance, etc.- Interdiffusion between org./org. interfaces- Trap formation at org./org. interfaces

21


2009. 1st Semester

Real-Time Observation of Temperature Rise and Thermal Breakdown Processes in Organic LEDs Using an IR Imaging and Analysis System

Joule heating


Xiang Zhou, Jun He, Liang S. Liao, Ming Lu, Xun M. Ding, Xiao Y. Hou, Xiao M. Zhang, Xiao Q. He, and Shuit T. Lee, Adv. Mater. 12, 265 (2000)


2009. 1st SemesterImpact of Joule heating on the brightness homogeneity of OLEDs

Brightness distribution of a device having anactive area of 15 cm2 at a current density of 33.3 mA/cm2.


C. Gärditz, A. Winnacker, F. Schindler, R. Paetzold, Appl. Phys. Lett. 90, 103506 (2007)

22


2009. 1st SemesterCoulombic degradation scaling law

Y. Sato, Electroluminescence I, edited by G. Mueller (Academic Press, San Diego, 2000) pp. 209-254.


C. Féry, B. Racine, D. Vaufrey, H. Doyeux, and S. Cinà, Appl. Phys. Lett. 87, 213502 (2005)

constant ; =∝ − ττ no

n LJ

1.7n constant. tL 1/20 ==×n


2009. 1st SemesterDegradation due to H2O permeation


M. Schaer, F. Nüesch, D. Berner, W. Leo, and L. Zuppiroli, Adv. Funct. Mater. 11, 116 (2001).

(d)

23


2009. 1st SemesterEncapsulation


P. E Burrows, G. L. Graff, M. E. Gross, P. M. Martin, M. Hall, E. Mast, C. Bonham, W. Bennett, L. Michalski, M. Weaver, J. J.Brown, D. Fogarty, L. S. Sapochak, Proceedings of SPIE 4105, 75 (2001).


2009. 1st Semester

•Inorganic:•Aluminum oxide deposited by DC reactive sputtering•Thickness 30-100 nm•Organic:•Monomer mixture deposited in vacuum•Non-conformal deposition: Liquid-Vapor-Liquid- (UV curing)-Solid•Thickness 0 25 several mm

Thin film encapsulation

Liquid precursor

(monomer)

Inorganic barrier

depositionCureLiquid

precursor (monomer) Cure

•Thickness 0.25 – several mm•4-5 polymer / inorganic pairs (dyads) for encapsulation


L. L. Moro, T. A. Krajewski, N. M. Rutherford, O. Philips, R. J. Visser, M. E. Gross, W. D. Bennett, and G. L. Graff, Proceedings of SPIE 5214, 83 (2004).

24


2009. 1st SemesterMethods of Full Color Display Fabrication

RGB method Color conversion method Color filter method

ETL

Cathode CathodeETL

CathodeETL

Glass

Anode

HTL

Blue emitting layerETL

Anode

Color conversion filter

HTL

White emitting layerAnode

Color filter


Red Green Blue

Glass

Red Green Blue

Glass

Red Green Blue


2009. 1st Semester

ItemsEvaporation

(Precision Shadow Mask)Ink-JetPrinting

Laser-InducedThermal Imaging (LITI)

M i l

Molecular Materials Only Polymer (LEP) Polymer (LEP)Molecular MaterialsHybrids (Blend)

Comparison of OLED color patterning methods

Materials

Printing Accuracy ± 15㎛ ± 15㎛ ± 2.5㎛

Resolution ~180ppi ~150ppi ~300ppi

Aperture Ratio40 50% 60% 70 80%


p(Top Emission)

40~50% ~60% 70~80%

Materials Usage - Smallest -Glass Size 730x460mm (~2005) 730x920mm 730x920mm (~2005)

Machine Price Very Expensive Cheapest MiddleSource: Samsung SDI, FPD int. 2004

25


2009. 1st SemesterPMOLED

Data Line(Anode : ITO)


Scan Line (Cathode : Al)


2009. 1st SemesterAMOLED

IC

TFTOLED pixel

TFT backplane

ITOHILHTL

ETLCathode

EML

＋

－

COLUMN DRIVERS(DATA VOLTAGE)

DR

IVER

SLE

CT

SIG

NAL

)

Metal Cathode Transparent Anode

Translucent Cathode

Transparent Plate

Light

Emissive Layer

Buffer Layer

FPC

Driver IC

Light Emission

GlassITO

RO

W

(PIX

EL S

EL

Power LineVDD

Scan Line

Data LineVDATA


Bottom Emission Top Emission

Al WiringLight

Metal Anode

Emissive Layer

DrivingTR

C

Light

SwitchingTR OLED

RGB

26


2009. 1st SemesterAM OLED Process Map

TFT Backplane Heat Treatment Washing Surface TreatmentOxygen plasma…etc

Organic LayerDeposition

Hole injection, transport layers

RGB materialDepoisition

Color patterning

Shadow MaskCleaning

Shadow MaskTension & Align

InspectionModule

Scribing


Organic LayerDeposition

ETL…Cathode DepositionSealing

Encap.glass

cleaning

g

Source: B. D. Chin (KIST), IMID 2006

advantages of oleds

Documents