maximizing oled lighting efficacy
TRANSCRIPT
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
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]
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
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]
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
0.10
0.15
0.20
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.