Non-fullerene acceptor photostability and its impact on organic solar cell lifetime
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. ; Funding Agencies|European Social Fund via the Welsh Government; EPSRCUK Research & Innovation (UKRI)Engineering & Physical Sciences Research Council (EPSRC) [EP/L015099/1, EP/T026219/1, EP/S020748/1]; UK EPSRCUK Research & Innovation (UKRI)Engineering & Physical Sciences Research Council (EPSRC) [EP/L016702/1]; ATIP Programme grant [EP/T028513/1]; CSEM Brasil; Global Research Laboratory Program of the National Research Foundation (NRF) - Ministry of Science, ICT & Future Planning [NRF-2017K1A1A2013153]; UKRI Global Challenge Research Fund project, SUNRISE [EP/P032591/1]; Office of Sponsored Research (OSR) [OSR-2018-CRG/CCF-3079, OSR-2019-CRG8-4086, OSR-2018-CRG7-3749]; European Social Fund, European Union CSEM Brasil, Brazil European Research Council, European Union ERC Synergy Grant [SC2 (610115)]; European Unions Horizon 2020 research and innovation programme [952911]; project BOOSTER [862474]; project RoLA-FLEX; KAUSTKing ...