Berlin 2018 – wissenschaftliches Programm

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 39: Organic Photovoltaics II

CPP 39.1: Hauptvortrag

Mittwoch, 14. März 2018, 09:30–10:00, C 243

Charge generation and recombination in an organic BHJ solar cell with low energetic offsets — •Thuc-Quyen Nguyen — Department of Chemistry and Biochemistry, University of California, Santa Barbara

Organic bulk heterojunction (BHJ) solar cells require energetic offsets between the donor and acceptor to obtain high short-circuit currents and fill factors. However, it is necessary to reduce the energetic offsets to achieve high open-circuit voltages. Recently, reports have highlighted BHJ blends that are pushing at the accepted limits of energetic offsets necessary for high efficiency. How the energetic offset impacts the solar cell characteristics thus remains poorly understood. We attempt to characterize the losses in BHJ blends that achieves a high open-circuit voltages with very low energy losses from the energy of absorbed photons. Despite the low energetic offset, the system does not suffer from field dependent generation and instead it is characterized by very fast nongeminate recombination and the presence of shallow traps. The charge-carrier losses are attributed to suboptimal morphology due to high miscibility between a polymer donor and PC61 BM. These results hold promise that given the appropriate morphology, the device parameters such as short-circuit currents, open-circuit voltages and fill factors can all be improved, even with very low energetic offsets.