Non-halogenated and non-volatile solid additive for improving the efficiency and stability of organic solar cells

Various high boiling point solvent additives are commonly used for high-performing organic solar cells (OSCs). However, they are not only usually detrimental to device stability but also often contain halogens, rendering them highly reactive and environmentally unfriendly. Herein, a non-halogenated and non-volatile solid additive, 2-(4-phenoxybenzylidene)-1 H -indene-1,3(2 H )-dione ( PID ), is synthesized for the preparation of high-performing and highly stable non-fullerene acceptor (NFA)-based OSCs. PID introduction enhances the molecular ordering of the photoactive materials and optimizes their nanoscale phase-separated morphology by controlling intermolecular interactions. The power conversion efficiency (PCE) of the resulting PID -processed OSC devices increases from 13.9% to 16.3%, surpassing that of 1-chloronaphthalene (CN)-processed devices (15.5%). Moreover, when burn-in losses are eliminated, the PID -processed devices demonstrate excellent thermal stability, retaining 98% of their initial PCE after 1200 h at 85 °C. Such high thermal stability renders these devices among the most stable PM6 : Y6 -based OSCs reported to date. The results suggest that non-volatile solid additives can simultaneously enhance the efficiency and stability of OSC devices without halogens, thereby opening up possibilities for their future commercial applications. A non-halogenated and non-volatile solid additive PID can interact simultaneously with donor and acceptor molecules and stabilize the bulk-heterojunction morphology, increasing the efficiency and thermal stability of organic solar cell devices.