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 journalArticlepeer-review

48 Citations (Scopus)

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 languageEnglish
Pages (from-to)7524-7537
Number of pages14
JournalOptics Express
Volume22
Issue number7
DOIs
Publication statusPublished - 25 Mar 2014

Keywords

  • Light-emitting diodes
  • Microstructure fabrication
  • Organic materials
  • Gratings

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