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Proceedings Paper

Surface plasmon polariton modification in top-emitting organic light-emitting diodes for enhanced light outcoupling
Author(s): Cornelius Fuchs; Tobias Schwab; Martin Wieczorek; Malte C. Gather; Simone Hofmann; Karl Leo; Reinhard Scholz
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Paper 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.

Paper Details

Date Published: 8 October 2014
PDF: 10 pages
Proc. SPIE 9183, Organic Light Emitting Materials and Devices XVIII, 91831Z (8 October 2014); doi: 10.1117/12.2061585
Show Author Affiliations
Cornelius Fuchs, Technische Univ. Dresden (Germany)
Tobias Schwab, Technische Univ. Dresden (Germany)
Martin Wieczorek, Technische Univ. Dresden (Germany)
Malte C. Gather, Technische Univ. Dresden (Germany)
Univ. of St. Andrews (United Kingdom)
Simone Hofmann, Technische Univ. Dresden (Germany)
Karl Leo, Technische Univ. Dresden (Germany)
Reinhard Scholz, Technische Univ. Dresden (Germany)


Published in SPIE Proceedings Vol. 9183:
Organic Light Emitting Materials and Devices XVIII
Franky So; Chihaya Adachi, Editor(s)

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