Bi-directional organic light-emitting diodes with nanoparticle-enhanced light outcoupling

Hong-Wei Chang, Jonghee Lee, Tae-Wook Koh, Simone Hofmann, Bjoern Luessem, Seunghyup Yoo*, Chung-Chih Wu, Karl Leo, Malte C. Gather

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

19 Citations (Scopus)

Abstract

An effective method is presented for enhancing the outcoupling efficiency of translucent/bi-directional organic light-emitting diodes (TL/BD-OLEDs) with a bottom indium tin oxide (ITO) anode and a top cathode comprised of a thin Ag layer covered with an organic capping layer. Upon insertion of a nanoparticle (NP)-based scattering layer (NPSL) between the substrate and the ITO anode, the TL/BD-OLEDs exhibit significantly enhanced external quantum efficiency (EQE) in both emission directions. Furthermore, the NPSL improves the color stability of the TL/BD-OLEDs over a wide range of viewing angles. Simulations based on geometrical and statistical optics are performed to elucidate the mechanism by which the efficiency is enhanced and to establish strategies for further optimization. Simulations performed on the scattering layers with varying NP volume percentage reveal that the bottom-side emission is governed by competition between waveguide-mode extraction and backward scattering by NPs in the film, while the top-side emission is largely dominated by the latter. Optimized bi-directional OLEDs achieve a 1.64-fold enhanced EQE compared to reference devices without NPSL.

Original languageEnglish
Pages (from-to)1079-1087
Number of pages9
JournalLaser & Photonics Reviews
Volume7
Issue number6
DOIs
Publication statusPublished - Nov 2013

Keywords

  • bi-directional organic light emitting diodes
  • nanoparticle scattering layer
  • outcoupling enhancement
  • DEVICES
  • EFFICIENCY
  • ELECTRODE
  • EMISSION
  • LAYER

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