Portal de Periódicos da CAPES

Understanding the Electronic Structure of Metal/SAM/Organic−Semiconductor Heterojunctions

2009; American Chemical Society; Volume: 3; Issue: 11 Linguagem: Inglês

10.1021/nn9010494

1936-086X

Ferdinand Rissner, Gerold Rangger, Oliver Hofmann, Anna Maria Track, Georg Heimel, Egbert Zojer,

Organic Electronics and Photovoltaics

Computational modeling is used to describe the mechanisms governing energy level alignment between an organic semiconductor (OSC) and a metal covered by various self-assembled monolayers (SAMs). In particular, we address the question to what extent and under what circumstances SAM-induced work-function modifications lead to an actual change of the barriers for electron and hole injection from the metal into the OSC layer. Depending on the nature of the SAM, we observe clear transitions between Fermi level pinning and vacuum-level alignment regimes. Surprisingly, although in most cases the pinning occurs only when the metal is present, it is not related to charge transfer between the electrode and the organic layer. Instead, charge rearrangements at the interface between the SAM and the OSC are observed, accompanied by a polarization of the SAM.