Non-fullerene acceptors end-capped with an extended conjugation group for efficient polymer solar cells

We report two novel small-molecule non-fullerene acceptors, IF-TN and IDT-TN, with indenofluorene (IF) and indacenodithiophene (IDT) as their respective central electron-rich cores and naphthyl-fused indanone (N) as the electron-withdrawing end-groups. By pairing these non-fullerene acceptors with a widely used polymer PBDB-T, the fabricated polymer solar cells based on PBDB-T: IDT-TN obtain a power conversion efficiency up to 5.89%, associated with a relatively high open-circuit voltage of 0.97 V and a remarkably low non-radiative open-circuit voltage loss of 0.23 V. These findings provide an effective approach for the rational molecular design of small-molecule acceptors with low non-radiative open-circuit voltage loss.