Universal Display Corporation

Maximizing OLED Lighting Efficacy

Ruiqing (Ray) Ma and Mike Weaver

DOE Workshop

Long Beach, LA, Jan 30, 2013

OLED Efficacy: Current Status

Pixel Efficacy = LER x IQE x OC x EEF

LER = Luminous Efficacy of Radiation ( = Max efficacy of emission spectra) IQE = Internal Quantum Efficiency OC = Outcoupling Efficiency EEF = Electrical Efficiency Factor ( = Optical Energy Gap/Applied Voltage)

Current Status LER [lm/W] 327 IQE [%] ~90% OC [%] ~40% EEF [%] ~70% Pixel Efficacy [lm/W] 80 (at 1,000 cd/m2)

There is a lot more!

Uses high index glass and a macroextractor

Without Outcoupling

With Outcoupling

Luminance [nits] 1,000 1,000

PE [lm/W] 45 120

CRI 82 82

EQE [%] 24 60

Voltage [V] 4.0 3.7

1931 CIE (0.438, 0.417) (0.438, 0.417)

Duv 0.005 0.005

CCT [K] 3091 3091

Efficacy Enhancement 1.00x 2.67x

Cathode

Anode HIL

Red-Green EML

Blue EML

ETL

High Index Glass

BL

HTL

Warm White

High Index glass hemisphere

4

WOLED Efficacy

VoutIQE

p

ηη∝η

Minimize

Maximize

• Power efficiency η P • Internal Quantum Efficiency η IQE

• Outcoupling efficiency η OUT

• Device voltage V

Maximize

VoutIQE

p

ηη∝η

• Power efficiency η P • Internal Quantum Efficiency η IQE

• Outcoupling efficiency η OUT

• Device voltage V Maximize

WOLED Efficacy

Phosphorescence Is Core to Maximizing IQE

Phosphorescent Emitters Enable OLED Lighting with IQE ≈ 100% → Approximately 4x higher IQE than fluorescent OLEDs

→ Much less heat within the device

Spin-orbit coupling via heavy metal atom (e.g. Pt or Ir)

M.A. Baldo, et. al., Nature., 1998

Host Guest

So So

S1 S1 T1 T1

Tran

sfer

ISC Phosphorescent OLEDs

Higher IQE Lower Temperature

Longer Lifetime

0

0.2

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0.8

1

350 400 450 500 550 600 650 700 750 800

Nor

mal

ized

EL

inte

nsity

[a.u

.]

Wavelength [nm]

New Red Emitter for Lighting Applications 8

0 1,000 2,000 3,000 4,000 5,0000

10

20

30

40

Luminance [cd/m2]

Lum

inous

Effic

acy [

cd/A

]

0

5

10

15

20

25

30E.Q.E.[%

]

At 1,000 cd/m2: LE = 29 cd/A EQE= 25% LT95% = 23,000h LT50% = 600,000h

620 nm

RED Monochrome PHOLED with EQE = 25%

Bottom-Emission Lambertian Device with no Outcoupling Enhancement

0 1,000 2,000 3,000 4,000 5,0000

20

40

60

80

100

Luminance [cd/m2]

Lum

inou

s Ef

ficac

y [c

d/A]

0

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25E.Q

.E.[%]

0

0.2

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350 400 450 500 550 600 650 700 750 800

Nor

mal

ized

EL

inte

nsity

[a.u

.]

Wavelength [nm]

9 New Yellow Emitter for Lighting Applications

At 1,000 cd/m2: LE = 81 cd/A EQE= 24% LT95% = 85,000h LT50% = 1,450,000h

Yellow Monochrome PHOLED with EQE = 24%

558 nm

Bottom-Emission Lambertian Device with no Outcoupling Enhancement

0 1,000 2,000 3,000 4,000 5,0000

10

20

30

40

50

60

Luminance [cd/m2]

Lum

inou

s Ef

ficac

y [c

d/A]

0

5

10

15

20

25E.Q

.E.[%]

0

0.2

0.4

0.6

0.8

1

350 400 450 500 550 600 650 700 750 800

Nor

mal

ized

EL

inte

nsity

[a.u

.]

Wavelength [nm]

10 Light Blue Emitter for Lighting Applications

At 1,000 cd/m2: LE = 50 cd/A EQE= 22% LT95% = 700h LT50% = 20,000h

Light Blue Monochrome PHOLED with EQE = 22%

Bottom-Emission Lambertian Device with no Outcoupling Enhancement

476 nm

0 1000 2000 3000 4000 50000

10

20

30

40

50

60

70

80

Luminance [cd/m2]

Lum

inou

s Ef

ficie

ncy

[cd/

A]

0

5

10

15

20

25

30

35

40EQ

E [%]

Light Blue Monochrome PHOLED with EQE ≈ 31%

λmax = 474 nm

400 450 500 550 600 650 700 750

0.00

0.05

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0.25

0.30

0.35

EL In

tens

ity [W

/sr/m

2 ]

Wavelength [nm]

At 1,000 cd/m2: LE = 69 cd/A EQE = 31%

Bottom-Emission Lambertian Device with no Outcoupling Enhancement

Light Blue PHOLED for Lighting: High EQE

VoutIQE

p

ηη∝η

• Power efficiency η P • Internal Quantum Efficiency η IQE

• Outcoupling efficiency η OUT

• Device voltage V

Maximize

WOLED Efficacy

Optical Outcoupling Challenge

Pixel

Panel

~ 50%

~ 20%

~ 30%

n = 1.0

n = 1.5

n = 1.7 ~ 2.0

Extracting Substrate Mode

Sun et al., Nature Photonics, 2008, 2, 483. Moller et al., J. Applied Physics, 2002, 91, 3324.

D’Andrade, Appl. Phys. Lett., 88 (2006) 192908 Y.H. Cheng et al., Appl. Phys. Lett., 90 (2007) 091102

Reineke et al., Nature, 2009, 459, 234.

Chang et al., Organic Electronics, 13 (2012) 1073-1080

Sun et al., Nature Photonics, 2008, 2, 483. Koh et al., Advanced Materials, 2010, 22, 1849.

Extracting ITO/Organic Mode

D Yokoyama, J. Mater. Chem. Oct 2011.

Orientation and Surface Plasmon Mode

D.K. Gifford, D.G. Hall, Appl. Phys. Lett. 81 (2002) 4315.

OLED Efficacy: Current Status & Targets

Pixel Efficacy = LER x IQE x OC x EEF

LER = Luminous Efficacy of Radiation ( = Max efficacy of emission spectra) IQE = Internal Quantum Efficiency OC = Outcoupling Efficiency EEF = Electrical Efficiency Factor ( = Optical Energy Gap/Applied Voltage)

Current Status Targets LER [lm/W] 327 350 IQE [%] ~90% 95% OC [%] ~40% 60%* EEF [%] ~70% 90% Pixel Efficacy [lm/W] 80 (at 1,000 cd/m2) 180 (at 3,000 cd/m2)

White OLED Pixel Efficacy Target = 180 lm/W

White PHOLEDs already emit with IQE ≈ 100% at low luminance. Challenge is to maintain IQE ≈ 95% at 3,000 cd/m2.