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DS: Fachverband Dünne Schichten

DS 21: Organic Electronics and Photovoltaics IV (joint session with CPP, HL, O)

DS 21.6: Vortrag

Mittwoch, 2. April 2014, 10:45–11:00, ZEU 260

Electronic Structure of Fullerene Heterodimer in Bulk-Heterojunction Blends — •Andreas Sperlich¹, Oleg G. Poluektov², Jens Niklas², Kristy L. Mardis³, and Vladimir Dyakonov¹ — ¹Experimental Physics VI, Julius Maximilian University of Würzburg and ZAE Bayern, 97074 Würzburg — ²Chemical Sciences and Engineering Division, ANL, Argonne, Illinois 60439, USA — ³Department of Chemistry and Physics, Chicago State University, Chicago, Illinois 60628, USA

To increase performance of organic solar cells, the optimization of the electron-accepting fullerenes has received less attention. Here, we report an electronic structure study of a novel covalently linked C₆₀-C₇₀-heterodimer in blend with the polymer PCDTBT. Upon optical excitation of polymer:heterodimer solid films, the electron is shared between both C₆₀ and C₇₀ cages. In contrast, in the solution the electron is localized on one half of the dimer. Electronic structure calculations reveal that for the heterodimer two nearly iso-energetic minima exist, essentially the cis and trans conformers. These conformers have different edge-to-edge distance between the two cages and therefor the electron is either shared between two dimer halves (cis) or localized on one half of the heterodimer (trans). By comparison with the experimental data, we conclude that the cis conformation is preferable in films, and the trans conformation in solution. These findings demonstrate how electronic coupling of the fullerene acceptor molecules is influenced by their packing in blends, which may have an impact on the charge carrier generation efficiency in solar cells.