Suppressing Photooxidation of Non-fullerene Acceptors and Their Blends in Organic Solar Cells by Exploring Material Design and Employing Friendly Stabilizers
In addition to a high power conversion efficiency, ambient stability is another impact factor for the successful commercialization of organic solar cells (OSCs). Understanding the role of photovoltaic materials is the key to address this challenge, but no such studies have been systematically analyzed to non-fullerene acceptors (NFAs). In this work, we firstly investigate the role of NFAs photooxidation in device degradation. Relevant investigation of physical dynamics underline the effects of NFAs photooxidation acting as trap states in exposed blends on device performance. In addition, taking ITIC as an example, we shed some light on the possible mechanisms of NFAs photooxidation, which can not be eliminated by explored strategies and principles of material design. Despite, these results drive us to further investigate the photobleaching rates of thirty-three NFAs, including fused-ring electron acceptors and perylene diimide acceptor derivatives. Surprisingly, most of them show the higher optical density loss as compared to their fullerene-based counterparts. In view of relevant comparative analysis in the discussion section, we further propose some design strategies to improve photooxidation stability of NFAs. More importantly, we find a stabilizer (namely nickel chelate S6) that can effectively suppress photooxidation of NFAs and their blends, and thus improved ambient stability of OSCs.