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HLUS Research Div.
Simulating Plasmon Effect in Nanostructured OLED Cathode Using COMSOL Multiphysics
Leiming WangKonica Minolta Laboratory USA Inc.
10/08/2015
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HLUS Research Div.
Lightweight
Thin
Flexible
Konica Minolta OLED lighting
One piece of cutting-edge technology creates the future
Flexible
Konica Minolta OLED lighting
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HLUS Research Div.
Konica Minolta OLED lighting
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HLUS Research Div.
Multilayer structure and light out-coupling of OLED
Typical power distribution spectrum of anOLED viewed in the k-space*
*Reineke et al., Rev. Mod. Phys. 85, 1245–1293 (2013) 4
HLUS Research Div.
Visualizing field distribution in OLED in real space
|Ex|
|Ey|
|E|
Py @ 475 nm
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HLUS Research Div.
Visualizing field distribution in OLED in real space
Px @ 475 nm
|Ey|
Pz @ 475 nm
|Ez|
SPP coupling is less for horizontally oriented dipole emission.
No SPP coupling for s-polarized case in 2D.6
HLUS Research Div.
Reducing waveguide mode by high index substrate
Regular glass
High refractive index glass
|Ey|
|Ey|
Py @ 475 nm.
Strategy of enhancing light extraction efficiency of OLED:plasmon mode waveguide mode substrate mode air mode. 7
HLUS Research Div.
Reducing SPP coupling by nanograting electrode
Light in air
Light in EML
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HLUS Research Div.
Reducing SPP coupling by nanograting electrode
Simplified model – Ag/EML two layer. Py @ 535 nm. Grating: λG = 100 nm, L = 50 nm, h = 50 nm, d = 50 nm, Δx = 0. 9
HLUS Research Div.
Reducing SPP coupling by nanograting electrode
3D capable, but memory intensive and time-consuming
|Ez|
Pz @ 535 nm
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HLUS Research Div.
Power flow analysis
SPP evanescent field (e-1)
Plasmon loss (%) = Pplasmon/Ptotal
0)( SdHEPtotal
⋅×= ∫1)( SdHEPlight
⋅×= ∫∫∫ ⋅⋅+⋅×= Agplasmon dVEJSdHEP )()( 2
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HLUS Research Div.
Total emission power
0.00E+00
5.00E+08
1.00E+09
1.50E+09
2.00E+09
2.50E+09
3.00E+09
3.50E+09
4.00E+09
0 50 100 150 200
Tota
l rad
iate
d po
wer
(Wat
ts/m
)
d (nm) (Δx=0)
flatλG = 100 nmλG = 300 nm
Py=1A•m @ 535 nm
Total emission power correlates with the decay rate of the molecular emitter andthe internal quantum efficiency (IQE) of OLED. For all-phosphorescent OLED, the IQE is ~100%; only the percentage of plasmonloss is concerned. 12
HLUS Research Div.
Plasmon loss – vertical dipole
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
0 50 100 150 200
Plas
mon
loss
(%)
d (nm)(Δx=0)
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
-150 -100 -50 0 50 100 150
Plas
mon
loss
(%)
Δx (nm)(d=50 nm)
Py @ 535 nm
flatλG = 100 nmλG = 300 nm
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HLUS Research Div.
Plasmon loss – horizontal dipole
Px @ 535 nm
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
-150 -100 -50 0 50 100 150
Plas
mon
loss
(%)
Δx (nm)(d=50nm)
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
0 50 100 150 200
Plas
mon
loss
(%)
d (nm)(Δx=0)
flat
λG = 100 nmλG = 300 nm
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HLUS Research Div.
Effect on emission patternFlat
λG = 50 nm |E|
|E|
|E|
λG = 100 nm
λG = 300 nm
λG = 1000 nm
|E|
|E|
Py @ 535 nm.
Δx = 0, d = 50nm,h=50nm, L/λG = ½.
Large grating may lead to structured directional emission.
Subwavelength grating –metasurface.
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HLUS Research Div.
Parametric studyRelative plasmon loss
0.37
SD of wavelength averaging
0.09
Relative ratio of plasmon loss - grating with respect to flat. λG = 100nm, d = 50 nm. Average of 2 horizontal positions: Δx = 0, Δx = λG/2. Average of Px and Py. Average of 3 emission wavelength: 475 nm, 535 nm, 625nm. COMSOL Multiphysics® Cluster Sweep – parallel! 16
HLUS Research Div.
Summary
Mode distribution and plasmon coupling effect in OLED were modeledusing COMSOL Multiphysics®, which can simulate the optical effectcaused by arbitrary subwavelength nanostructures.
Reduction of plasmon loss in OLED by ~ 50% over broadbandemission is promising by nanostructured metal cathode.
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HLUS Research Div.
Acknowledgement
Stanford UniversityProf. Mark BrongersmaMr. Majid Esfandyarpour
Konica Minolta Inc. (Japan)Mr. Toshihiko IwasakiMr. Masahiro ImadaOLED groupSimulation group
HLUSDr. Jun AmanoDr. Po-Chieh Hung
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