Regensburg 2019 – scientific programme

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 9: Organic Electronics and Photovoltaics I - Charge Transport and Electronic Devices

CPP 9.3: Talk

Monday, April 1, 2019, 15:45–16:00, H18

Electronic couplings in molecular crystals: Tight-Binding fits vs. cluster-based approaches — •Florian Mayer, Christian Winkler, and Egbert Zojer — Institute of Solid State Physics, NAWI Graz, Graz University of Technology, Petersgasse 16, 8010 Graz, Austria

The ever-growing interest in electronic properties of new materials triggers the development of new methodologies for their reliable description. For modelling charge-transport properties, theories span the full range from band transport via dynamic-disorder models to hopping approaches. For all these methods the electronic coupling between neighboring molecules is a crucial input. This quantity can be calculated with various approaches most of them relying on simulations of molecular dimers and small clusters. In contrast, the fitting of extended Tight-Binding models to full band structures allow the evaluation of intermolecular coupling, treating the molecules in their actual crystalline environments. In the present contribution, for the prototypical examples of pentacene and quinacridone, applying the above-mentioned complementary approaches, we discuss issues like next-nearest neighbor coupling, interference between different coupling directions for coherent transport, and how to deal with off-Gamma point band extrema. For non-periodic calculations we also present a new variant of the fragment orbital and electronic splitting method. The obtained results provide insight into the strengths and limitations of the various approaches and help to better understand electronic coupling in organic semiconductors.