Berlin 2015 – wissenschaftliches Programm
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DF: Fachverband Dielektrische Festkörper
DF 11: Small Polarons in LiNbO3
DF 11.6: Vortrag
Mittwoch, 18. März 2015, 11:20–11:40, EB 133C
Light-induced polaron transport in 1, 2, and 3-dimensional systems — •Christoph Merschjann1,2 and Stefan Lochbrunner1 — 1Institut für Physik, Universität Rostock, D-18051 Rostock, Germany — 2Freie Universität Berlin, D-14195 Berlin, Germany
Transient optical spectroscopy of functional materials is frequently used to extract important electronic quantities, such as the nature of the photoexcitations (e.g., excitons or separated charge carriers, polarons, etc.), their concentrations, and mobilities. This is especially helpful for powders or microcrystalline samples which do not allow for macroscopic investigations like, e.g., standard conductivity measurements. The most prominent experimental techniques are pump-probe transient-absorption measurements and time-resolved fluorescence investigations. Very often, non-exponential decays of the transient spectra are observed, which are too frequently left unexplained or misinterpreted.
We apply a random-walk approach to model diffusion-type transports of light-induced charge carriers (e.g., small polarons). The obtained set of rate equations reveals distinct power-law behaviors for the decays of transient absorption and fluorescence. Typical phenomena like geminate and bimolecular recombination are clearly distinguishable. From the characteristics, one is able to directly deduce not only the dimensionality of the transport, but also mobilities and concentrations of the involved carriers.