Regulating Crystallization of A-D-A-Type Fused Acceptors for Enhanced Stability of Organic Solar Cells: Role of Recognition Interactions with Volatilizable Additives

Despite significant progress in the development of organic solar cells (OSCs) in the past two decades, the stability of nonfullerene acceptors (NFAs) has been a persistent challenge. This study presents a solution to this issue by incorporating a sterically hindered radical precursor, tris(2,4,6-trichlorophenyl)methane (HTTM), into the active layer of OSCs based on NFAs such as ITIC. Recognition interactions between the HTTM and the acceptor, such as C–H···N hydrogen bonding between the proton-donating center of HTTM and the end groups of the acceptor, are observed. Besides, the volatilization of HTTM under thermal annealing can regulate the crystallization behavior of the acceptors. The recognition interactions and the regulated crystallization together inhibit the oxidation process of the acceptors, thus significantly improving the photochemical stability of the blend films and devices. This work highlights the potential of radical precursors as antioxidants for acceptor materials in OSCs and provides a perspective for the development of stable OSCs.