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Improved Light Outcoupling from OLED by Non-Wave-Guiding Anode Designs

Published online by Cambridge University Press:  13 February 2014

M. Slawinski
Affiliation:
Device Technology, RWTH Aachen University, Sommerfeldstr. 24, 52074 Aachen, Germany
M. Brast
Affiliation:
Device Technology, RWTH Aachen University, Sommerfeldstr. 24, 52074 Aachen, Germany
X. D. Zhang
Affiliation:
Device Technology, RWTH Aachen University, Sommerfeldstr. 24, 52074 Aachen, Germany
F. Merget
Affiliation:
Integrated Photonics, Sommerfeldstr. 24, RWTH Aachen University, 52074 Aachen, Germany
J. Witzens
Affiliation:
Integrated Photonics, Sommerfeldstr. 24, RWTH Aachen University, 52074 Aachen, Germany
M. Heuken
Affiliation:
Device Technology, RWTH Aachen University, Sommerfeldstr. 24, 52074 Aachen, Germany AIXTRON SE, Kaiserstr. 98, 52134 Herzogenrath, Germany
A. Vescan
Affiliation:
Device Technology, RWTH Aachen University, Sommerfeldstr. 24, 52074 Aachen, Germany
H. Kalisch
Affiliation:
Device Technology, RWTH Aachen University, Sommerfeldstr. 24, 52074 Aachen, Germany
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Abstract

We improve the efficiency of a bottom-emitting red phosphorescent organic light emitting diode (OLED) by the suppression of wave-guided modes in the bottom contact. ITO as bottom contact layer has been substituted by a thin Ti/Au layer. Electromagnetic simulation results of both devices predict the absence of TE polarized guided contact modes by the use of 10 nm Au as bottom electrode. We measured an improved outcoupling of light which overcompensates absorption losses of the Ti/Au layer in the measured emission cone. By the use of 1 nm Ti as undercoat, a continuous Au film of 8 nm thickness could be realized with an improved transmittance for long wavelengths (λ > 550 nm). As a consequence of fewer lateral guided modes, the external quantum efficiency (EQE) has been enhanced from 11.5 % of the standard device to 14 % of the device with the Ti/Au electrode.

Type
Articles
Copyright
Copyright © Materials Research Society 2014 

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References

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