Regensburg 2019 – scientific programme
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CPP: Fachverband Chemische Physik und Polymerphysik
CPP 31: Organic Electronics and Photovoltaics II - Non-Fullerene Organic Solar Cells
CPP 31.2: Talk
Wednesday, April 3, 2019, 09:45–10:00, H18
Analysing geminate and non-geminate losses in high performance non-fullerene blends — •Lorena Perdigón-Toro1, Huotian Zhang2, Safa Shoaee1, Feng Gao2, and Dieter Neher1 — 1University of Potsdam, Institute of Physics and Astronomy, Germany — 2Linköping University, Department of Physics, Chemistry and Biology (IFM), Sweden
Organic solar cells consist of blends of two or more semiconductors with different electronic structures, namely organic electron donors and acceptors. Recently, interest has increased towards non-fullerenes (NF) as the small-molecule acceptor. Organic cells benefit from the NF long wavelength absorption, which provides the blend with a broader coverage of the sun spectrum and thus, higher short-circuit currents. Moreover, devices containing NFs show high open-circuit voltages meaning that charge separation occurs efficiently even with small driving forces. In this work we study charge generation and recombination in a set of NF devices with efficiencies up to 13%. While all blends exhibit similar low voltage losses, the fill factors (FF) of the solar cells differ greatly, pointing to significant differences in geminate and/or non-geminate recombination. Time delayed collection field (TDCF) and bias assisted charge extraction (BACE) were used to disentangle these processes. Indeed, the devices with lower FF suffer from field-dependence of charge generation and faster bimolecular recombination. Altogether, the obtained recombination coefficients together with SCLC-measured mobilities allow reconstructing the FF, clearly pointing to these parameters as those to address for higher overall performance.