Coherent mode coupling in highly efficient top-emitting OLEDs on periodically corrugated substrates

Tobias Schwab; Cornelius Fuchs; Reinhard Scholz; Alexander Zakhidov; Karl Leo; Malte Christian Gather

doi:10.1364/OE.22.007524

Coherent mode coupling in highly efficient top-emitting OLEDs on periodically corrugated substrates

Tobias Schwab, Cornelius Fuchs, Reinhard Scholz, Alexander Zakhidov, Karl Leo, Malte Christian Gather

Research output: Contribution to journal › Article › peer-review

Abstract

Bragg scattering at one-dimensional corrugated substrates allows to improve the light outcoupling from top-emitting organic light-emitting diodes (OLEDs). The OLEDs rely on a highly efficient phosphorescent pin stack and contain metal electrodes that introduce pronounced microcavity effects. A corrugated photoresist layer underneath the bottom electrode introduces light scattering. Compared to optically optimized reference OLEDs without the corrugated substrate, the corrugation increases light outcoupling efficiency but does not adversely affect the electrical properties of the devices. The external quantum efficiency (EQE) is increased from 15 % for an optimized planar layer structure to
17.5 % for a corrugated OLED with a grating period of 1.0mm and a
modulation depth of about 70 nm. Detailed analysis and optical modeling
of the angular resolved emission spectra of the OLEDs provide evidence
for Bragg scattering of waveguided and surface plasmon modes that are
normally confined within the OLED stack into the air-cone. We observe
constructive and destructive interference between these scattered modes and
the radiative cavity mode. This interference is quantitatively described by a
complex summation of Lorentz-like resonances.

Original language	English
Pages (from-to)	7524-7537
Number of pages	14
Journal	Optics Express
Volume	22
Issue number	7
DOIs	https://doi.org/10.1364/OE.22.007524
Publication status	Published - 25 Mar 2014

Keywords

Light-emitting diodes
Microstructure fabrication
Organic materials
Gratings

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10.1364/OE.22.007524

schwab2014opticsexpress7524
(C) 2014 OSA. This paper was published in Optics Express and is made available as an electronic reprint with the permission of OSA. The paper can be found at the following URL on the OSA website: http://www.opticsinfobase.org/. Systematic or multiple reproduction or distribution to multiple locations via electronic or other means is prohibited and is subject to penalties under law.
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title = "Coherent mode coupling in highly efficient top-emitting OLEDs on periodically corrugated substrates",

abstract = "Bragg scattering at one-dimensional corrugated substrates allows to improve the light outcoupling from top-emitting organic light-emitting diodes (OLEDs). The OLEDs rely on a highly efficient phosphorescent pin stack and contain metal electrodes that introduce pronounced microcavity effects. A corrugated photoresist layer underneath the bottom electrode introduces light scattering. Compared to optically optimized reference OLEDs without the corrugated substrate, the corrugation increases light outcoupling efficiency but does not adversely affect the electrical properties of the devices. The external quantum efficiency (EQE) is increased from 15 % for an optimized planar layer structure to17.5 % for a corrugated OLED with a grating period of 1.0mm and amodulation depth of about 70 nm. Detailed analysis and optical modelingof the angular resolved emission spectra of the OLEDs provide evidencefor Bragg scattering of waveguided and surface plasmon modes that arenormally confined within the OLED stack into the air-cone. We observeconstructive and destructive interference between these scattered modes andthe radiative cavity mode. This interference is quantitatively described by acomplex summation of Lorentz-like resonances.",

keywords = "Light-emitting diodes, Microstructure fabrication, Organic materials, Gratings",

author = "Tobias Schwab and Cornelius Fuchs and Reinhard Scholz and Alexander Zakhidov and Karl Leo and Gather, {Malte Christian}",

note = "This work was funded by the European Social Fund and the Free State of Saxony through the OrganoMechanics project, and by the AIF/BMWi in the framework IGF under contract no. GF-11/05 resp. AiF-Nr. 16784 BR (project LipsOLED). Support from the excellence cluster cfaed is gratefully acknowledged. We acknowledge support by the German Research Foundation and the Open Access Publication Funds of the TU Dresden.",

year = "2014",

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doi = "10.1364/OE.22.007524",

language = "English",

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T1 - Coherent mode coupling in highly efficient top-emitting OLEDs on periodically corrugated substrates

AU - Schwab, Tobias

AU - Fuchs, Cornelius

AU - Scholz, Reinhard

AU - Zakhidov, Alexander

AU - Leo, Karl

AU - Gather, Malte Christian

N1 - This work was funded by the European Social Fund and the Free State of Saxony through the OrganoMechanics project, and by the AIF/BMWi in the framework IGF under contract no. GF-11/05 resp. AiF-Nr. 16784 BR (project LipsOLED). Support from the excellence cluster cfaed is gratefully acknowledged. We acknowledge support by the German Research Foundation and the Open Access Publication Funds of the TU Dresden.

PY - 2014/3/25

Y1 - 2014/3/25

N2 - Bragg scattering at one-dimensional corrugated substrates allows to improve the light outcoupling from top-emitting organic light-emitting diodes (OLEDs). The OLEDs rely on a highly efficient phosphorescent pin stack and contain metal electrodes that introduce pronounced microcavity effects. A corrugated photoresist layer underneath the bottom electrode introduces light scattering. Compared to optically optimized reference OLEDs without the corrugated substrate, the corrugation increases light outcoupling efficiency but does not adversely affect the electrical properties of the devices. The external quantum efficiency (EQE) is increased from 15 % for an optimized planar layer structure to17.5 % for a corrugated OLED with a grating period of 1.0mm and amodulation depth of about 70 nm. Detailed analysis and optical modelingof the angular resolved emission spectra of the OLEDs provide evidencefor Bragg scattering of waveguided and surface plasmon modes that arenormally confined within the OLED stack into the air-cone. We observeconstructive and destructive interference between these scattered modes andthe radiative cavity mode. This interference is quantitatively described by acomplex summation of Lorentz-like resonances.

AB - Bragg scattering at one-dimensional corrugated substrates allows to improve the light outcoupling from top-emitting organic light-emitting diodes (OLEDs). The OLEDs rely on a highly efficient phosphorescent pin stack and contain metal electrodes that introduce pronounced microcavity effects. A corrugated photoresist layer underneath the bottom electrode introduces light scattering. Compared to optically optimized reference OLEDs without the corrugated substrate, the corrugation increases light outcoupling efficiency but does not adversely affect the electrical properties of the devices. The external quantum efficiency (EQE) is increased from 15 % for an optimized planar layer structure to17.5 % for a corrugated OLED with a grating period of 1.0mm and amodulation depth of about 70 nm. Detailed analysis and optical modelingof the angular resolved emission spectra of the OLEDs provide evidencefor Bragg scattering of waveguided and surface plasmon modes that arenormally confined within the OLED stack into the air-cone. We observeconstructive and destructive interference between these scattered modes andthe radiative cavity mode. This interference is quantitatively described by acomplex summation of Lorentz-like resonances.

KW - Light-emitting diodes

KW - Microstructure fabrication

KW - Organic materials

KW - Gratings

U2 - 10.1364/OE.22.007524

DO - 10.1364/OE.22.007524

M3 - Article

SN - 1094-4087

VL - 22

SP - 7524

EP - 7537

JO - Optics Express

JF - Optics Express

IS - 7

ER -

Coherent mode coupling in highly efficient top-emitting OLEDs on periodically corrugated substrates

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