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 31.1: Talk

Wednesday, April 3, 2019, 09:30–09:45, H18

Loss Processes in Non-fullerene Acceptor Bulk Heterojunction Solar Cells — •Frédéric Laquai — King Abdullah University of Science and Technology, KAUST Solar Center, Thuwal, Saudi Arabia

Organic solar cells that use non-fullerene acceptors (NFA) are now outperforming their fullerene-based counterparts with efficiencies exceeding 14%. While the photophysics of fullerene-based systems have been studied quite intensively, the complex interplay between structure, morphology, photophysics, and efficiency of non-fullerene acceptor devices remains less well understood; yet, understanding the structure-property relations is an important prerequisite for a guided material design and further efficiency enhancements. In this contribution, I will discuss what currently limits the quantum efficiency in blends of common donor polymers and novel non-fullerene acceptors. By using steady-state and transient spectroscopy techniques and advanced data analysis tools, we are able to distinguish the spectral contributions and dynamics of singlet excitons, charge carriers, and triplet states and to quantify their concentration across a wide dynamic range relevant to the solar cell performance. Furthermore, we investigate how the CT-state energy, radiative, and non-radiative losses in non-fullerene acceptor blends influence the open-circuit voltage and we address the origin of low fill factors sometimes observed in NFA systems. This allows us to develop a precise picture of the efficiency-limiting processes in solar cells that use novel non-fullerene acceptors.