Non-fullerene acceptor photostability and its impact on organic solar cell lifetime
Andrew J. Clarke, Joel Luke, Rico Meitzner, Jiaying Wu, Yuming Wang, Harrison Ka Hin Lee, Emily M. Speller, Helen Bristow, Hyojung Cha, Michael Newman, Katherine Hooper, Alex Evans, Feng Gao, Harald Hoppe, Iain McCulloch, Ulrich S. Schubert, Trystan Watson, James R. Durrant, Wing Chung Tsoi, Ji‐Seon Kim, Zhe Li
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.