Berlin 2018 – wissenschaftliches Programm
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CPP: Fachverband Chemische Physik und Polymerphysik
CPP 46: Poster Session IV
CPP 46.37: Poster
Mittwoch, 14. März 2018, 11:00–13:00, Poster A
Composition control and photovoltaic properties of binary polymer:fullerene blends — •Lorena Perdigón-Toro1, Yueqi Yang1, Elisa Collado-Fregoso1, Harald Ade2, and Dieter Neher1 — 1University of Potsdam, Institute of Physics and Astronomy, Germany — 2Department of Physics and ORaCEL, North Carolina State University, Raleigh, North Carolina 27695, USA
Organic solar cells consist of blends of two or more semiconductors with distinct electronic structures, namely electron donors and acceptors. The morphology of the blend can vary greatly depending on numerous conditions, such as the nature of the materials or the processing. When employing an amorphous polymer and small molecules such as fullerenes, the morphology comprises at least two phases: one phase nearly pure in fullerenes and a second where the macromolecules and fullerenes are intimately intermixed. The initial polymer:fullerene ratio and the annealing temperature play deciding roles on the composition of these two phases. Recent work suggested an unique dependence of the fill factor of solar cells made from binary blends with composition contrast.
In this work, we use PCDTBT:PC71BM as reference to obtain a system ranging from a well-separated blend to a one phase blend. Devices annealed above the critical temperature exhibit much lower fill factor, pointing to increased geminate and/or non-geminate recombination. Various techniques such as bias assisted charge extraction (BACE) and time delayed collection field (TDCF) are used to disentangle these processes and analyse field-assisted charge generation and extraction.