Controlling the work function of ZnO and the energy-level alignment at the interface to organic semiconductors with a molecular electron acceptor

Raphael Schlesinger, Yong Xu, Oliver T. Hofmann, Stefanie Winkler, Johannes Frisch, Jens Niederhausen, Antje Vollmer, Sylke Blumstengel, Fritz Henneberger, Patrick Rinke, Matthias Scheffler, Norbert Koch

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Abstract

We show that the work function (Φ) of ZnO can be increased by up to 2.8 eV by depositing the molecular electron acceptor 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane (F4TCNQ). On metals, already much smaller Φ increases involve significant charge transfer to F4TCNQ. No indication of negatively charged F4TCNQ on ZnO is found by photoemission spectroscopy. This fundamental difference is explained by a simple electrostatic model that identifies the bulk doping and band bending in ZnO as key parameters. Varying Φ of the inorganic semiconductor enables tuning the energy-level alignment at ZnO/organic semiconductor interfaces.

Original languageEnglish
Article number155311
JournalPhysical Review B - Condensed Matter and Materials Physics
Volume87
Issue number15
DOIs
Publication statusPublished - 22 Apr 2013
Externally publishedYes

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ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Condensed Matter Physics

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