Surface plasmon polariton modification in top-emitting organic light-emitting diodes for enhanced light outcoupling

C. Fuchs, T. Schwab, M. Wieczorek, M.C. Gather, S. Hofmann, K. Leo, R. Scholz

Research output: Chapter in Book/Report/Conference proceedingConference contribution

5 Citations (Scopus)
2 Downloads (Pure)

Abstract

We report on the enhanced light outcoupling efficiency of monochrome top-emitting organic light-emitting diodes (OLEDs). These OLEDs incorporate a hole transport layer (HTL) material with a substantially lower refractive index (∼ 1:5) than the emitter material or the standard HTL material (∼ 1:8) of a reference device. This low-index HTL is situated between the opaque bottom metal contact (anode) and the active emission layer. Compared to an HTL with common refractive index, the dispersion relation of the surface plasmon polariton (SPP) mode from the opaque metal contact is shifted to smaller in-plane wavenumbers. This shift enhances the outcoupling efficiency as it reduces the total dissipated power of the emitter. Furthermore, the excitation of the coupled SPPs at the thin transparent metal top contact (cathode) is avoided by using an ultrathin top electrode. Hence, the coupling of the electroluminescence from the emitter molecules to all non-radiative evanescent modes, with respect to the emitter material, is reduced by at least a factor of two, additionally increasing the outcoupling efficiency. Furthermore, for sufficiently high refractive index contrast the shift of the SPP at the anode/organic interface can lead to in-plane wavenumbers smaller than the wavenumber within the organic emitter layer and outcoupling of all excited modes by high index light extraction structures, e.g. microlens, seems feasible. In accordance to optical simulations, the external quantum efficiency is enhanced by about 20% for monochrome green emitting OLEDs with low refractive index HTL compared to a reference sample.
Original languageEnglish
Title of host publicationOrganic Light Emitting Materials and Devices XVIII
EditorsF. So
PublisherSPIE
Volume9183
ISBN (Print)9781628412109
DOIs
Publication statusPublished - 2014
EventOrganic Light Emitting Materials and Devices XVIII - San Diego, United Kingdom
Duration: 17 Aug 201417 Aug 2014

Publication series

NameProceedings of SPIE
PublisherSPIE - The International Society for Optical Engineering
Volume9183
ISSN (Print)0277-786X

Conference

ConferenceOrganic Light Emitting Materials and Devices XVIII
Country/TerritoryUnited Kingdom
CitySan Diego
Period17/08/1417/08/14

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