Non-fullerene acceptor photostability and its impact on organic solar cell lifetime

Abstract
The development of non-fullerene acceptors (NFAs) has facilitated the realization of efficient organic solar cells (OSCs) with minimal burn-in losses and excellent long-term stability. However, the role of NFA molecular structures on device stability remains unclear, limiting commercialization of NFA-based OSCs. Herein, the photostability of 10 OSC devices, fabricated with various NFAs (O-IDTBR, EH-IDTBR, ITIC, and ITIC-M) blended with donor polymers (PTB7-Th, PffBT4T-2OD, and PBDB-T), is investigated. O-IDTBR and EH-IDTBR form highly stable devices with all three polymers, whereas ITIC and ITIC-M devices suffer from burn-in losses and long-term degradation. Conformational instability is found to be responsible for the poor photostability of ITIC and ITIC-M, resulting in poor device stability. Twisting and potential breakage of the chemical bond that links the end group to the main backbone of ITIC and ITIC-M molecules causes undesirable conformational changes. Potential strategies to overcome such detrimental photo-induced conformational changes in NFAs are proposed.

Citation
Clarke, A. J., Luke, J., Meitzner, R., Wu, J., Wang, Y., Lee, H. K. H., … Li, Z. (2021). Non-fullerene acceptor photostability and its impact on organic solar cell lifetime. Cell Reports Physical Science, 100498. doi:10.1016/j.xcrp.2021.100498

Acknowledgements
The authors thank all sources of funding that made this work possible. A.J.C. and W.C.T. acknowledge funding from the European Social Fund via the Welsh Government and EPSRC project EP/L015099/1. J.L. and J.-S.K. thank UK EPSRC for the Plastic Electronics Centre for Doctoral Training (EP/L016702/1) and ATIP Programme grant (EP/T028513/1) and CSEM Brasil for a CASE studentship. This research was also supported by the Global Research Laboratory Program of the National Research Foundation (NRF), funded by the Ministry of Science, ICT & Future Planning (NRF-2017K1A1A2013153). E.M.S. thanks the National Research Network in Advanced Engineering and Materials. J.R.D. and J.W. thank the UKRI Global Challenge Research Fund project, SUNRISE (EP/P032591/1). H.B. and I.M. acknowledge financial support from KAUST, including Office of Sponsored Research (OSR) awards OSR-2018-CRG/CCF-3079, OSR-2019-CRG8-4086, and OSR-2018-CRG7-3749, and funding from European Social Fund, European Union CSEM Brasil, Brazil European Research Council, European Union ERC Synergy Grant SC2 (610115), the European Union’s Horizon 2020 research and innovation programme under grant agreement 952911, project BOOSTER and grant agreement 862474, project RoLA-FLEX, and EPSRC project EP/T026219/1. Z.L. acknowledges EPSRC project EP/S020748/1.

Publisher
Elsevier BV

Journal
Cell Reports Physical Science

DOI
10.1016/j.xcrp.2021.100498

Additional Links
https://linkinghub.elsevier.com/retrieve/pii/S2666386421001983

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