Regensburg 2016 – scientific programme

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DS: Fachverband Dünne Schichten

DS 9: Organic Thin Films II

DS 9.1: Talk

Monday, March 7, 2016, 15:00–15:15, H11

Investigation of phase separation in bulk heterojunction organic solar cells — •Vladislav Jovanov, Arne Hendel, Nivedita Yumnam, and Veit Wagner — Jacobs University Bremen, Campus Ring 1, 28759 Bremen, Germany

Performances of bulk heterojunction organic solar cells strongly depend on their ability to dissociate photo-generated excitons. Efficient exciton dissociation is crucial for achieving high short circuit currents and energy conversion efficiencies. A volume distributed junction between donor and acceptor material is needed to obtain efficient dissociation, since exciton dissociation occurs only at their interface. Furthermore, the domain sizes of donor and acceptor material should be at nanometer length scale, so that excitons can reach the interface before they recombine. In this study, a phase separation of bulk heterojunction organic solar cells based on a blend mixture of PTB7 (donor) and PCBM (acceptor) material is investigated. To record the phase separation, an atomic force microscopy (AFM) has been used. The phase image measured by AFM depends on the energy dissipated by a cantilever tip to a material at the surface of a sample. Consequently, the phase contrast observed in the phase image is influenced by different materials present at the sample surface. By identifying the phase of donor and acceptor material, the phase separation and its dependence on preparation conditions can be determined from AFM phase image.