Vacuum-Deposited Donors for Low-Voltage-Loss Nonfullerene Organic Solar Cells.

The advent of nonfullerene acceptors (NFAs) enabled records of organic photovoltaics (OPVs) exceeding 19% power conversion efficiency in the laboratory. However, high-efficiency NFAs have so far only been realized in solution-processed blends. Due to its proven track record in upscaled industrial production, vacuum thermal evaporation (VTE) is of prime interest for real-world OPV commercialization. Here, we combine the benchmark solution-processed NFA Y6 with three different evaporated donors in a bilayer (planar heterojunction) architecture. We find that voltage losses decrease by hundreds of millivolts when VTE donors are paired with the NFA instead of the fullerene C60, the current standard acceptor in VTE OPVs. By showing that evaporated small-molecule donors behave much like solution-processed donor polymers in terms of voltage loss when combined with NFAs, we highlight the immense potential for evaporable NFAs and the urgent need to direct synthesis efforts toward making smaller, evaporable compounds.

Kaienburg, P., Bristow, H., Jungbluth, A., Habib, I., McCulloch, I., Beljonne, D., & Riede, M. (2023). Vacuum-Deposited Donors for Low-Voltage-Loss Nonfullerene Organic Solar Cells. ACS Applied Materials & Interfaces.

The authors would like to thank Yun Xiao for fabricating Y6 layers for initial feasibility testing. P.K. and M.R. acknowledge funding from the Global Challenges Research Fund (GCRF) through the Science & Technology Facilities Council (STFC), grant no. ST/R002754/1: Synchrotron Techniques for African Research and Technology (START). P.K. also thanks the EPSRC for funding a Postdoctoral Fellowship EP/V035770/1. H.B. acknowledges funding from the Department of Chemistry at the University of Oxford. A.J. acknowledges funding from the Wolfson-Marriott Graduate Scholarship from Wolfson College, Oxford, the EPSRC Doctoral Training Accounts, and the Department of Physics at the University of Oxford. I.H. acknowledges funding from the Oppenheimer Memorial Trust and the Firstrand Foundation. I.M. acknowledges financial support from the KAUST Office of Sponsored Research (OSR) CRG 10 award and partial funding by the European Union’s Horizon 2020 research and innovation programme under grant agreement no. 952911, BOOSTER grant agreement no. 862474, RoLA-FLEX, and grant agreement no. 101007084 CITYSOLAR, as well as EPSRC Project EP/T026219/1 and EP/W017091/1. D.B. is a research director of the Belgian National Fund for Scientific Research (FRS-FNRS). This research was funded in whole, or in part, by the UKRI grant EP/V035770/1. For the purpose of Open Access, the author has applied a CC BY public copyright licence to any Author Accepted Manuscript version arising from this submission.

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