Dresden 2017 – scientific programme

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 50: Poster: Organic Electronics and Photovoltaics, Molecular Excitations

CPP 50.17: Poster

Wednesday, March 22, 2017, 18:30–21:00, P3

Towards high-mobility polymorphs in organic semiconductors — •Daniel R. Reiterer, Simon Erker, Egbert Zojer, and Oliver T. Hofmann — Institute of Solid State Physics, NAWI Graz, Graz University of Technology, Austria

An important aspect for the application of organic semiconductors in practical devices is their charge-carrier mobility. However, in organic molecules the mobilities are often small. One of the reasons is that organic molecules tend to crystallize in polymorphs with a small band dispersion and that polymorphs with large dispersion tend to be energetically unfavorable. This is because increasing the intermolecular wave-function overlap, which would increase the band dispersion, also increases Pauli-repulsion. In this work, we discuss various strategies to mitigate or circumvent this effect in order to achieve high-mobility (high dispersion) polymorphs of organic semiconductors. For the example of pentacene we show that high-dispersion polymorphs can be stabilized when the antibonding states in the valence band are depleted. This can be achieved via doping or, to a lesser extent, via contact with passivated metal surfaces. Another possible strategy that we demonstrate here is the use of antiaromatic molecules such as cyclooctatetraene (COT).