The role of transition metal oxides in chargegeneration layers for stacked organic light-emitting diodes

Sami Hamwi, Jens Meyer, Michael Kröger, Thomas Winkler, Marco Witte, Thomas Riedl, Antoine Kahn, Wolfgang Kowalsky

Research output: Contribution to journalArticle

132 Scopus citations

Abstract

The mechanism of charge generation in transition metal oxide (TMO)-based charge-generation layers (CGL) used in stacked organic light-emitting diodes (OLEDs) is reported upon. An interconnecting unit between two vertically stacked OLEDs, consisting of an abrupt heterointerface between a Cs 2 CO 3 doped 4,7-diphenyl-1,10-phenanthroline layer and a WO 3 film is investigated. Minimum thicknesses are determined for these layers to allow for simultaneous operation of both sub-OLEDs in the stacked device. Luminance - current density - voltage measurements, angular dependent spectral emission characteristics, and optical device simulations lead to minimum thicknesses of the n-type doped layer and the TMO layer of 5 and 2.5 nm, respectively. Using data on interface energetic determined by ultraviolet photoelectron and inverse photoemission spectroscopy, it is shown that the actual charge generation occurs between the WO 3 layer and its neighboring hole-transport material, 4, 4', 4'-tris(N-carbazolyl)-triphenyl amine. The role of the adjacent n-type doped electron transport layer is only to facilitate electron injection from the TMO into the adjacent sub-OLED.

Original languageEnglish (US)
Pages (from-to)1762-1766
Number of pages5
JournalAdvanced Functional Materials
Volume20
Issue number11
DOIs
StatePublished - Jun 9 2010

All Science Journal Classification (ASJC) codes

  • Chemistry(all)
  • Materials Science(all)
  • Condensed Matter Physics

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