Fluoroalkyl-based near-infrared acceptors for morphology control enabling high-efficiency additive-free organic solar cells

Herein, a fluoroalkyl side chain modified A-DA'D-A small molecule acceptor, Y18-F9, was developed to optimize the bulk heterojunction morphology in organic solar cells. The introduction of fluorocarbon chains promotes self-assembly into nanoscale fibrous networks, while the low surface energy drive favorable vertical phase segregation. These synergistic effects lead to enhanced molecular packing, improved charge transport and collection, and reduced recombination losses. Consequently, the additive-free D18:L8-BO:Y18-F9 ternary OSCs achieves an impressive power conversion efficiency of 19.31% with a simultaneously enhanced short-circuit current density of 27.27 mA cm^-2 and fill factor of 79.7%.