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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 6: Electronic and Optical Properties of Organic Systems I

CPP 6.1: Topical Talk

Monday, March 22, 2010, 11:30–12:00, H39

Triplet exciton diffusion in organic semiconductors — •Anna Köhler — Department of Physics, University of Bayreuth, Bayreuth, Germany

Efficient triplet exciton emission has allowed improved operation of organic light-emitting diodes (LEDs). To enhance the device performance, it is necessary to understand what governs the motion of triplet excitons through the organic semiconductor. We use a series of poly(p-phenylene)-type conjugated polymers and oligomers of variable degree of molecular distortion (i.e. polaron formation) and energetic disorder as model systems to study the Dexter-type triplet exciton diffusion in thin films. We show that triplet diffusion can be quantitatively described in the framework of a Holstein small polaron model (Marcus theory) that is extended to include contributions from energetic disorder. The model predicts a tunnelling process at low temperatures followed by a thermally activated hopping process above a transition temperature. In contrast to charge transfer, the activation energy required for triplet exciton transfer can be deduced from the optical spectra. We discuss the implications for device architecture.