Approaching 19

Additives play a crucial role in enhancing the photovoltaic performance of polymer solar cells (PSCs). However, the typical additives used to optimize blend morphology of PSCs are still high boiling-point solvents, while their trace residues may reduce device stability. Herein, an effective strategy of “solidification of solvent additive (SSA)” has been developed to convert additive from liquid to solid, by introducing a covalent bond into low-cost solvent diphenyl sulfide (DPS) to synthesize solid dibenzothiophene (DBT) in one-step, which achieves optimized morphology thus promoting efficiency and device stability. Owing to the fine planarity and volatilization of DBT, the DBT-processed films achieve ordered molecular crystallinity and suitable phase separation compared to the additive-free or DPS-treated ones. Importantly, the DBT-processed device also possesses improved light absorption, enhanced charge transport, and thus a champion efficiency of 17.9