Integer Charge Transfer and Hybridization at an Organic Semiconductor/Conductive Oxide Interface

Marco Gruenewald, Laura K. Schirra, Paul Winget, Michael Kozlik, Paul F. Ndione, Ajaya K. Sigdel, Joseph J. Berry, Roman Forker, Jean-Luc Bredas, Torsten Fritz, Oliver L. A. Monti

Research output: Contribution to journalArticlepeer-review

59 Scopus citations


We investigate the prototypical hybrid interface formed between PTCDA and conductive n-doped ZnO films by means of complementary optical and electronic spectroscopic techniques. We demonstrate that shallow donors in the vicinity of the ZnO surface cause an integer charge transfer to PTCDA, which is clearly restricted to the first monolayer. By means of DFT calculations, we show that the experimental signatures of the anionic PTCDA species can be understood in terms of strong hybridization with localized states (the shallow donors) in the substrate and charge back-donation, resulting in an effectively integer charge transfer across the interface. Charge transfer is thus not merely a question of locating the Fermi level above the PTCDA electron-transport level but requires rather an atomistic understanding of the interfacial interactions. The study reveals that defect sites and dopants can have a significant influence on the specifics of interfacial coupling and thus on carrier injection or extraction.
Original languageEnglish (US)
Pages (from-to)4865-4873
Number of pages9
JournalThe Journal of Physical Chemistry C
Issue number9
StatePublished - Feb 25 2015

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KAUST Repository Item: Exported on 2020-10-01


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