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Getting All the Light Out: Light Extraction from Organic Light Emitting Devices
Yue Qu 1
Prof. Stephen Forrest 1,2,3
1 2018 SSL R&D workshop
1Department of Electrical Engineering and Computer Science, 2Physics Department, 3Department of Materials Science and Engineering,
University of Michigan, Ann Arbor
Motivation & Background
ηEQE = ηIQE (~100%1) × ηExt ≈ 20%
substrate modes waveguide modes surface plasmon modes
2
1Adachi et al, J. Appl. Phys. 90, 5048–5051 (2001)
2018 SSL R&D workshop
Air mode Substrate mode
Waveguide
SPP
Motivation & Background
As ETL increases
SPPs decrease Waveguide modes increase Substrate and air modes
fluctuate
3
0 20 40 60 80 100 120 1400
20
40
60
80
100
Frac
tion
of P
ower
(%)
ETL thickness (nm)
SPP WV
Sub Air
Abs.
2018 SSL R&D workshop
Sub-Anode Grid
A multi-wavelength scale dielectric grid between glass and transparent anode (sub-anode grid)
The grid layer is planar and non-intrusive into OLED active region
Waveguided light is scattered into substrate and air modes
4
Qu, Slootsky, Forrest, Nature Photonics (2016)
Cathode
nglass=1.5
nhost norg=1.7, nITO=1.8
ngrid ngrid
2018 SSL R&D workshop
Sub-Anode Grid
5
160nm grid/ 70nm ITO/ 2nm MoO3/40nm CBP/15nm CBP:Ir(ppy)3/xnm TPBi/1nm LiF/Al
2018 SSL R&D workshop
Thick-ETL organic structure: 340nm grid/70nm ITO/2nm MoO3/40nm TcTa/15nm CBP: Ir(ppy)3/10nm TPBi/230nm Bphen:Li/Al
Sub-Electrode Grid in TE-OLEDs
6 2018 SSL R&D workshop
Substrate Au Ag
SiO2 IZO Organic Capping layer
Metal reflector far away from the EML No excitation of SPPs
Grid >> optical wavelengths
The grid is planar and non-intrusive into the active region
control grid
Sub-Electrode Grid in TE-OLEDs
7 2018 SSL R&D workshop
Organic structure: MoO3 30nm/ BPhen: Li 30nm/ Bphen 30nm / CBP : Ir(ppy)3 25nm/ TAPC 40nm /MoO3 30nm/
Glass
Ag Substrate
Organic
IZO 50nm
IZO 50nm
MgF290nm
control grid
grid
control
Microlens on Top of TEOLEDs
9 2018 SSL R&D workshop
0 5 10 15 2010-4
10-3
10-2
10-1
100
101
102
J (m
A/c
m2 )
Voltage (V)
450 500 550 600 6500.0
0.2
0.4
0.6
0.8
1.0
MLA control
Inte
nsity
wavelength (nm)
0.1 1 10 1000
10
20
30
40
50
EQ
E(%
)
J (mA/cm2)
Ag
IZO 50nm
Organic
Substrate
SiO2 65nm
IZO 50nm
MLA
Organic structure: HatCN 30nm/ BPhen: Li 30nm/ Bphen 30nm / CBP : (acac)Ir(ppy)2 30nm/ TAPC 40nm / HatCN 30nm/
Flexible Corrugated Substrates
10 2018 SSL R&D workshop
Ultra-thin (~μm) Flexible Light extraction from substrate, waveguide and SPP modes
a a
Flexible Corrugated Substrates
11
0 5 10 15 2010-7
10-5
10-3
10-1
101
103
glass flat parylene corrugated parylene
J (m
A/c
m2 )
Voltage (V)
0.01 0.1 1 10 1005
10
15
20
25
30
35
glass flat parylene corrugated parylene
EQ
E(%
)
J (mA/cm2)400 450 500 550 600 650 700 750
0.0
0.2
0.4
0.6
0.8
1.0
Inte
nsity
wavelength (nm)
70nm ITO/2nm MoO3/40nm TAPC/25nm CBP: Ir(ppy)2acac/65nm TPBi/LiQ/Al
2018 SSL R&D workshop
High RI
Conclusions & Discussions
Four light extraction methods Non-intrusive structures can be better in light extraction Substrates integrated with outcoupling structures are applicable
for both top and bottom emitting OLEDs Wavelength & angle independent outcoupling methodes
12 2018 SSL R&D workshop
Low RI
Scattering layer
Metal/abs. materials
Acknowledgements
DoE SSL Program (DE-EE0007626) Universal Display Corporation Lurie Nanofabrication Facility
13 2018 SSL R&D workshop
