hi h ffi i hit oled f di lhigh efficiency white oled for...

Hi h ffi i hit OLED f di lHigh efficiency white OLED for display and lighting applicationsand lighting applications

2009.09.18

Jun Yeob Lee

Organic Electronics Laboratory, Dankook University, Korea

White light-emitting diodes

G l li h iLi h

Application of white OLEDs

General lightingLight sourceni

t)In

tens

ity (a

rb. u

GE Philips400 500 600 700 800

Wavelength (nm)

Device structure of white OLEDsSingle layer white OLEDsSimple device structure

Stacked white OLEDsGood device performances

Device structure of white OLEDs

Poor device performancesSuitable for polymers

pGood color stabilitySuitable for small molecules

RGB or YB

Materials for white OLED

Fluorescent OLED Phosphorescent OLED

Emission process

Singlet to singlettransition

Triplet to singlet transition

Efficiency 25 %(internal efficiency) 100 %(internal efficiency)25% 75% 100%

Emitter Organic or organometallic Organometallic(Ir, Pt, Os,…complex)

N

Emission Singlet Triplet

NIr

N

Emission mode

Singlet Triplet

High efficiency phosphorescent white OLEDs

All phosphorescent white OLEDs

Quantum efficiency : > 15 %, Q y ,Lifetime : >200,000 h@1,000 cd/m2

CIE : (0.47,0.45)

UDC, SID 2008

High efficiency phosphorescent white OLEDs

Hybrid white OLEDs

Singlet blue/red and green tripletQuantum efficiency : 18.4%

Forrest et al. Nature. 440, 908(2006)

High efficiency phophorescent white OLEDs

Tandem OLED(Multiphotoemission)

Emission Layer Hole Transport Layer

Electron Transport LayerCathode

Cathode

Emissive unit Glass substrate

AnodeHole Injection Layer Hole Transport Layer

Charge generation layer

Emissive unitEmissive unit

Charge generation layer

Emissive unitAnode

ITO, WO3, V2O5, NPD:F4-TCNQ

BCP:Li, BCP:Cs

White lightForrest et al. Adv. Mater. 18, 339(2006)

Comparison of white OLEDs

All phosphorescent

hybrid tandem

Quantum efficiency 15 ~ 20 % 15 ~ 20 % 20 ~ 35 %

Driving voltage 5 ~ 6 V 5 ~ 6 V ~ 8-9 V

Color purity bad good goodp y g g

Lifetime >100, 000 h >100, 000 h >> 100,000 h

Bl lif i Bl lif iProblem

Blue lifetimeColor stability

Efficiency roll-off

Blue lifetimeColor stability

Efficiency roll-off

Complicated process

Efficiency roll-offEfficiency roll off Efficiency roll off Efficiency roll off

Comparison of OLED as a display and lighting

Display lightingDisplay

휘도 : 100 ~ 500 cd/m2

수명 : >10 000 30 000 h

lighting

휘도 : >1000 cd/m2

수명수명 : >10,000 ~ 30,000 h높은 색순도

고정세넓은 색재현 범위

수명 : >10,000 h높은 연색지수대면적 구현

넓은 색재현 범위낮은 소비전력

TFT 구동

낮은 소비전력저가 공정 구현

Key performances of white OLEDs

High quantum efficiencyHigh quantum efficiency

Low driving voltage : P-I-NHigh mobility common layer

C l t bilit b l d bi ti hiftColor stability : balanced recombination zone shift

Little efficiency roll-off : little charge leakageLittle efficiency roll off : little charge leakagebroad recombination zone

High color rendering index for lighting

P re RGB emission for displaPure RGB emission for display

High quantum efficiency in sky blue and white OLED for lightingwhite OLED for lighting- New blue phosphorescent host material

- New orange phosphorescent host material

Advantages of spiro structure

•High thermal stability

•Morphological stability•Morphological stability

•Good Electron transporting properties

•Photochemical stability•Photochemical stability

•Blue emission

•Chemical versatility•Chemical versatility

•Wide triplet bandgap(2.9 eV)

Synthesis of SPPO1

PCl

MC SPPO 1341 nmP

PO

Br

MC

H2O2

0.15

0.20

UV

SPPO 1BG = 324 nm, 3.82eVET = 444 nm, 2.79 eV

Ia.u.

) 0.8

1.0444 nm308, 316 nm341 nm

PL at 77K PL at 298K

2-diphenylphosphine oxide-9,9′-spirobifluorene (SPPO1)

0.05

0.10

ntensity(a.u.)Abs

orba

nce(

a

0.4

0.6

300 400 500 6000.00

0.05 )A

Wavelength(nm)

0.0

0.2

Wavelength(nm)

J. Y. Lee et al. submitted (2008)

Device performances of SPPO1

25 mCP

LiF/Al (200 nm) Quantum efficiency : 17 %

15

20SPPO1 PEDOT/SPPO1 PEDOT/TCTA/SPPO1

Effic

ienc

y (%

)Alq3 (20 nm)

SPPO1:FIrpic (30 nm,10%)BCP (5 nm)

mCP (5 nm)

(0.15,0.33)

0

5

10

Qua

ntum

E

NPB (20 nm)

ITO

DNTPD (60 nm)

ITO

DNTPD (60 nm)

40

8000

0 1 10 100 1000 100000

Luminance (cd/m2)

ITOITOGlass

30

40

ty(m

A/c

m2 )

mCP SPPO1 PEDOT/SPPO1 PEDOT/TCTA/SPPO1 6000

8000 mCP SPPO1 PEDOT/SPPO1 PEDOT/TCTA/SPPO1

e (c

d/m

2 )

10

20

Cur

rent

Den

sit

2000

4000

Lum

inan

ce0 2 4 6 8 10

0

Voltage(V)0 2 4 6 8 10

0

Voltage (V)

SPPO1 in simple device structure

Q. E. : 19.4 %(0 15 0 33)(0.15,0.33)

J. Y. Lee et al. Appl. Phys. Lett. 94, 013301(2009)

SPPO1 as a host in WOLEDs

SPPO1

LiF/Al 120

cm2 ) 15000

Device I(current density) 20

%) 50

A)

mCP

SPPO1:Firpic:Ir(pq)2acac

SPPO1

TCTA 60

90

ensit

y (m

A/c

6000

9000

12000

ance

(cd/

m2 )Device II(current density)Device I (luminance)Device II(luminance)

8

12

16

m e

ffici

ency

(%

20

30

40

effic

ienc

y (c

d/A

Device I(quantum eff )

ITO

PEDOT:PSS

NPB

0

30

Cur

rent

de

0

3000

6000

Lum

ina

0

4

8

1 10 100 1000 10000

Qua

ntum

0

10

20

Cur

rent

eDevice I(quantum eff.)Device II(quantum eff.)Device I(current eff.)Device II(current eff.)

D i I d 0 7 %

2.4 2 72.42.4

0 2 4 6 8

Voltage (V)

1 10 100 1000 10000

Luminance (cd/m2)Device I : red 0.7 %Device II : red 1.0 %

NPD

2.4 2.7

2.8

PEDOT

3.1

BCP

2.42.8

Alq3

3.0

FIrpic

TCTA

2.4

Ir(pq)2acac

3.0

(arb

. uni

t) Device I

Device II

5.5 5.6mCP

5.1

BCP

6.1 SPPO1 6.1

Alq3

5.85.7

5.2

Inte

nsity

6.5 400 500 600 700 800

Wavelength (nm)

J. Y. Lee et al. Optics Letters. 34, 407(2009)

Stacked WOLEDs

J. Y. Lee et al. submitted(2009)

Stacked WOLEDs

(0.37,0.43) 27.5 cd/A

New SPPO2 material

Roughness : 0.3 nm Triplet energy : 2.4 eVJ. Y. Lee et al. J. Mat. Chem. In press(2009)

SPPO2 as an electron transport material

Electron only device high electron density in the SPPO2

SPPO2 as the electron transport layer in green

SPPO2 as an electron transport material in blue

Phosphorescent orange host material

J. Y. Lee et al. Org. Electron. 10, 998(2009)

Deep blue and pure white phosphorescent OLED for displayOLED for display

deep blue phosphorescent device- deep blue phosphorescent device

- pure white phosphorescent devicep p p

Deep blue phosphorescent materials

(0.13,0.14)

BASF SID 2006

Deep blue phosphorescent materials

Chi et al. Adv. Mater. ASAP 2009 Wu et al. Angew. Chem. Int. Ed. 47, 4542 2008

Blue phosphorescent dopant materials

NIr

FN

Ir

NIr

FN

I

F

3

NC

FIr

FNC

F

F

3

Ir

3333

475 nm 464 nm 452 nm523 nm

Blue shift by electron withdrawing substituent in phenylBlue shift by electron donating substituent in pyridine

Deep blue phosphorescent dopant materials

(0.15, 0.16), 11 cd/A


Pure white OLEDs using deep blue material

LiF/Al

Alq3

LiF/Al

Alq3

LiF/Al

Alq3

LiF/Al

Alq3

mCP:FCNIr(20 nm)

BCP

q3

TCTA:TAZ:Ir(ppy)3:Ir(pq)2acac

mCP:FCNIr(15 nm)

BCP

q3


mCP:FCNIr(10 nm)

BCP

q3


mCP:FCNIr(15 nm)

BCP

q3

TCTA:TAZ:Ir(ppy)3:Ir(pq)2acac30 nm

TCTA

ITO

PEDOT:PSS

NPB

mCP

ITO

PEDOT:PSS

NPB

mCP

ITO

PEDOT:PSS

NPB

mCP

ITO

PEDOT:PSS

NPB

mCP

100D i I

10000

ITO ITO ITO ITO

Device I Device II Device III Device IV

60

80

nsity

(mA

/cm2 ) Device I

Device IIDevice IIIDevice IV 6000

8000

nce

(cd/

m2 )

Device I

Device II

Device III

Device IV

20

40

Cur

rent

den

2000

4000

Lum

inan

00 2 4 6 8 10

Voltage (V)

00 2 4 6 8 10

Voltage (V)


Pure white OLEDs using deep blue material

CIE Current ffi iefficiency

Device I (0.28,0.31) 21 cd/A

Device II (0.30,0.31) 21 cd/A

30

Device III (0.35,0.34) 25 cd/A

Device IV (0.30,0.31) 28 cd/A

20

25

30

cy (c

d/A

)

uni

t) Device IDevice IIDevice III

10

15

ent e

ffici

enc

Device IDevice II en

sity

(arb

. Device IIIDevice IV

0

5

0 2000 4000 6000 8000 10000

Cur

re Device IIIDevice IV

400 500 600 700 800

Inte

0 2000 4000 6000 8000 10000Luminace (cd/m2)

400 500 600 700 800

Wavelength (nm)

EL spectra according to luminance

t) (0.30,0.33)

(arb

. uni

t (0.30,0.33)

7500 cd/m2

(0.30,0.31)

630 cd/m2

Inte

nsity

630 cd/m

400 500 600 700 800

I

(0.29,0.31)

270 cd/m2

400 500 600 700 800

Wavelength (nm)

New fabrication method of WOLEDNew fabrication method of WOLED

- stamp transfer printingstamp transfer printing

Stacked polymer white light-emitting diodes

Stacked double layer emitting structure in polymer white LEDs

toluene soluble

alcohol soluble

Xie et al. Appl. Phys. Lett. 90, 203513, 2007

Printing method to form orthogonal polymer filmsPrinting method to form orthogonal polymer filmsTransfer printing Laser induced thermal imaging

Bradley et al. Adv. Mater. 20, 1679, 2008 Lee et al. Adv. Mater. 16, 51, 2004

Stamp transfer printing process

SiITO

Yellow polymerPEDOT:PSS

PDMS

metal cathode

J. Y. Leet et al. Org. Electron. 10, 372(2009)

AFM of Yellow Polymer Films

S i ti St t f i tiSpin coatingSurface roughness : 0.5 nm

Stamp transfer printingSurface roughness : 0.4 nm

Comparison of hole only devices

Hole current density increase by stamp transfer printing

ITO/PEDOT:PSS/SY/Al

35004000

A/c

m2 )

spin coatingT f i ti

2000

25003000

nsity

(mA Transfer printing

Yellow polymer

Al

++ + + + +

++ + + + +

500

10001500

urre

nt d

en

ITO

PEDOT:PSS

0500

0 1 2 3 4 5

V lt (V)

Cu

Voltage (V)

Comparison of device performances

Current density and luminance increase by stamp transfer printingC t ffi i i b t t f i tiCurrent efficiency increase by stamp transfer printing

ITO/PEDOT:PSS/SY/LiF/Al

2000

)

30000 4

1500

y (m

A/c

m2 )

20000

25000

ce (c

d/m2 )Spin coating

Transfer printing3

ency

(cd/

A)

500

1000

rent

den

sity

10000

15000

Lum

inan

c1

2

rren

t effi

cie

Spin coating

00 1 2 3 4 5

Cur

0

5000

00 5000 10000 15000 20000 25000 30000

Cur Transfer printing

Voltage (V) Luminace (cd/m2)

Comparison of emission spectrum

Same spectrum irrespective of film coating method

. uni

t) Spin coating

Transfer printing

nsity

(arb

.In

ten

400 500 600 700 800

Wavelength (nm)

Comparison of lifetime

Lifetime was doubled by stamp transfer printing process

Current density : 40 mA/cm2

80

100

) 4

4.5spin coatingTransfer printing

60

nanc

e (%

3.5

4

tage

(V)

20

40

Lum

in

3

Vol

t

00 50 100 150 200

2.5

Time (h)

Stamp transfer printing of soluble small molecules

J. Y. Leet et al. Org. Electron. 10, 978(2009)

Stamp transfer printing process for white deviceSi

ITOSi

ITO



PDMS Blue polymerPDMS Blue polymer

l h dl h dmetal cathodemetal cathode

J. Y. Leet et al. J. Phys. D. 42, 105115(2009)

Multilayer white polymer light-emitting device

2.4

2.5Low current density in the white device due to poor 2.9

PEDOTBl

YellowLiF/Al

hole injection into blue emitting layer

5.1

4.85.0

Blue

ITO

5.4

1000

cm2 ) B(30 nm)/Y(30 nm)

B(20 nm)/Y(20 nm) 80009000

10000

m2 )

B(30 nm)/Y(30 nm)B(20 nm)/Y(20 nm)B(30 nm)

600

800

nsity

(mA

/c B(30 nm)Y(30 nm)

40005000600070008000

nanc

e (c

d/m2 B(30 nm)

Y(30 nm)

200

400

Cur

rent

den

01000200030004000

Lum

in

00 1 2 3 4 5 6 7 8

Voltage (V)

00 1 2 3 4 5 6 7 8

Voltage (V)

Efficiency of WPLEDs

High efficiency compared with corresponding single layer devices

5

4

5y

(cd/

A) B(30 nm)/Y(30 nm)

B(20 nm)/Y(20 nm)B(30 nm)Y(30 nm)

2

3

t effi

cien

cy

0

1

Cur

rent

00.1 1 10 100 1000 10000

Luminace (cd/m2)

Electroluminescence spectra of WPLEDs

Balanced red and green emission in multilayer WPLEDs

Color coordinate (0.34, 0.41)

unit)

B(30nm)/Y(30nm)B(20nm)/Y(20nm)B(30 nm)

ity (a

rb. u Y(20 nm)

Inte

nsi

400 500 600 700 800

W l th ( )Wavelength (nm)

WPLEDs with QD interlayer

QD interlayer forcolor control in WPLEDs

J. Y. Leet et al. Appl. Phys. Lett. 94, 093303(2009)

AcknowledgementS. O. Jeon (Ph.D, 4학기)- OLED material synthesis- Organic memory

S. U. Jang (MS, 2학기)- OLED material synthesis

g y- Organic solar cell

K S Yook (Ph D 1학기) H. S. Son (MS, 2학기)K. S. Yook (Ph.D, 1학기)- White OLED- Organic bistable LED

H. S. Son (MS, 2학기)- OLED material synthesis- Solar cell material synthesis

C. W. Joo (MS, 4학기)- Polymer WOLED Undergraduate

Y. J. Cho C. W. Suh

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