Bifunctional Bis-benzophenone as A Solid Additive for Non-Fullerene Solar Cells

Simultaneously improving efficiency and stability is critical for the commercial application of non-fullerene acceptor polymer solar cells (NFA-PSCs). Multifunctional solid additives have been considered as a potential route to tune the morphology of the active layer and optimize performance. In this work, photoinitiator bifunctional bis-benzophenone (BP-BP) is used as a solid additive, replacing solvent additives, in the PBDB-T:ITIC NFA system. With the addition of BP-BP, the intermolecular pi-pi stacking of PBDB-T and morphology is improved, leading to more balanced carrier transport and more effective exciton dissociation. Devices fabricated with BP-BP show a power conversion efficiency (PCE) of 11.89%, with enhanced short-circuit current (J(sc)), and fill factor (FF). Devices optimized with BP-BP show excellent reproducibility, insensitivity to thickness, and an improved thermal stability under atmospheric conditions without encapsulation. This work provides a new strategy for the application of solid additives in NFA-PSCs.