Regensburg 2010 – scientific programme

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SYDI: Symposium SKM Dissertation Prize 2010

SYDI 1: SKM Dissertation Prize 2010

SYDI 1.3: Invited Talk

Tuesday, March 23, 2010, 14:30–15:00, H10

Charge Transport in Organic Crystals — •Frank Ortmann — Friedrich-Schiller-Universität Jena, Institut für Festkörpertheorie und -optik, Jena, Germany — CEA Grenoble, France

The understanding of basic principles of charge transport in semiconductors with varying strength of electron-phonon interaction is still a great challenge. The complex interplay between moving electrons and phonons results in a variety of transport phenomena that evaded a comprehensive description within a single approach so far. Only for certain limits such as band transport in crystalline structures with weak electron-phonon coupling or phonon-assisted hopping in disordered systems with strong electron-phonon coupling one can easily come up with reduced models for carrier transport. This is not possible, however, for organic crystals which are important benchmark systems to understand carrier transport in organic materials.

I present a novel approach that describes carrier transport for arbitrary strength of the electron-phonon coupling including the temperature-dependent crossover from band transport to hopping in organic crystals. The polaronic nature and motion of localized carriers at high temperatures is obtained as well as the band motion for delocalized particles at low temperatures. The theory, supplemented with material parameters obtained from density-functional theory, allows for a systematic study of carrier transport in organic crystals. As a prototypical example, the simulated carrier mobilities for naphthalene crystals show clear improvements with respect to measured values both for the temperature dependence and for the mobility anisotropy.