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Optics Express

Optics Express

  • Editor: Andrew M. Weiner
  • Vol. 22, Iss. 7 — Apr. 7, 2014
  • pp: 7524–7537

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

Tobias Schwab, Cornelius Fuchs, Reinhard Scholz, Alexander Zakhidov, Karl Leo, and Malte C. Gather  »View Author Affiliations


Optics Express, Vol. 22, Issue 7, pp. 7524-7537 (2014)
http://dx.doi.org/10.1364/OE.22.007524


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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 1.0 μm 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.

© 2014 Optical Society of America

OCIS Codes
(050.2770) Diffraction and gratings : Gratings
(160.4890) Materials : Organic materials
(230.3670) Optical devices : Light-emitting diodes
(230.4000) Optical devices : Microstructure fabrication

ToC Category:
Optoelectronics

History
Original Manuscript: September 18, 2013
Revised Manuscript: November 28, 2013
Manuscript Accepted: December 19, 2013
Published: March 25, 2014

Citation
Tobias Schwab, Cornelius Fuchs, Reinhard Scholz, Alexander Zakhidov, Karl Leo, and Malte C. Gather, "Coherent mode coupling in highly efficient top-emitting OLEDs on periodically corrugated substrates," Opt. Express 22, 7524-7537 (2014)
http://www.opticsinfobase.org/oe/abstract.cfm?URI=oe-22-7-7524


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