Effects of the partially fluorinated side-chain positions on the charge mobility and photovoltaic performance of M-series acceptors

• • N5F, with fluorinated side-chains on nitrogen, achieves a PCE of 18.8% and FF of 80.7%, outperforming O5F (PCE 17.8%, FF 79.2%), representing a 1.0% absolute PCE improvement. • • PM6:N5F devices exhibit a T80 lifetime of 1084 hours under 1-sun illumination, an 8.8-fold enhancement over PM6:O5F (123 hours), indicating superior operational stability. • • N5F shows closer π-π stacking distance and enhanced charge mobility compared to O5F, directly correlating with improved photovoltaic performance. • • The 18.8% PCE is among the highest reported for A-D-A-type fused-ring-based NFAs, highlighting the effectiveness of partially fluorinated side-chain positioning.