Dresden 2017 – wissenschaftliches Programm
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CPP: Fachverband Chemische Physik und Polymerphysik
CPP 50: Poster: Organic Electronics and Photovoltaics, Molecular Excitations
CPP 50.5: Poster
Mittwoch, 22. März 2017, 18:30–21:00, P3
Ultrafast Dynamics of Charge Transfer in Polymer-Fullerene Systems — •Stefan Wedler1, Thomas Unger1, Heinz Bässler2, and Anna Köhler1,2 — 1Experimental Physics II, University of Bayreuth, 95440 Bayreuth, Germany — 2Bayreuth Institute of Macromolecular Research (BAMF)
Exciton dissociation in organic semiconductors is a two-step process that consists first of an initial transfer of an electron from the photoexcited donor to the acceptor and second of the subsequent separation process of the resulting Coulomb-bound interfacial electron-hole pair. Here, we have explored whether the initial electron transfer is thermally activated and can thus be described by a Markus-type rate, or whether it is a temperature-independent tunneling-type process that is best modelled by a Miller-Abrahams rate. In order to investigate the influence of thermal activation on the transfer dynamics, we have performed temperature dependent ultrafast pump-probe spectroscopy on films of three polymer-PCBM blends with a resolution of 200 fs. The charge transfer is measured by monitoring the transient absorption of the polymer cation after excitation. So far we find no change in transfer dynamics upon cooling to low temperatures within our temporal resolution. This result suggests that initial charge transfer lacks thermal activation.