Unraveling UV Degradation Pathways in Inverted Organic Solar Cells Incorporating A-DA'D-A Type Non-Fullerene Acceptors

Operational stability is the main obstacle to the industrial applications of organic solar cells (OSCs). In this study, different degradation mechanisms under continuous simulated solar radiation are demonstrated for high-performance non-fullerene OSCs based on commonly used electron transport materials, i.e., ZnO and SnO2. The ZnO-induced decomposition pathways of A-DA'D-A type non-fullerene acceptors (NFAs) under UV illumination are unraveled for the first time and related to N-dealkylation of pyrrole from the core moiety. In the case of SnO2, poor photo-stability is primarily ascribed to a high density of trap states, which can be diminished by surface modification to achieve better device stability that is comparable with the stability under LED illumination without UV components. With a thorough understanding of the degradation pathways, this study provides valuable guidelines for designing high-performance and stable non-fullerene OSCs. Evidence of ZnO-induced decomposition of A-DA'D-A type NFA under UV illumination is demonstrated in this work. Using SnO2 as an alternative ETL, performance degradation of OSCs is mainly ascribed to a high concentration of surface defects, which can be overcome by amine modification of the SnO2 surface. image