Near-infrared absorbing non-fullerene acceptors with selenophene as π bridges for efficient organic solar cells

Abstract

Two non-fullerene acceptors with selenophene π bridges to link the indacenodithiophene (IDT) core and 3-(dicyanomethylidene)indan-1-one (IC) or difluorinated IC (2F-IC) terminals, i.e.IDT2Se and IDT2Se-4F, were synthesized. IDT2Se and IDT2Se-4F have low optical band gaps (E^opt_g) of 1.45 and 1.39 eV, respectively. Organic solar cells (OSCs) based on them were fabricated with the wide band gap polymer PBDB-T as the donor. A wide photo-current response extending to 850 and 900 nm was observed for the IDT2Se and IDT2Se-4F based devices, respectively. Besides, the PBDB-T:IDT2Se-4F blend film exhibited higher electron mobility and more balanced hole and electron transport ascribed to the higher packing order of IDT2Se-4F in the blends and a proper phase-separated morphology. As a result, the IDT2Se-4F based devices delivered a high power conversion efficiency (PCE) up to 11.19% with an open-circuit voltage (V_oc) of 0.79 V, a short-circuit current density (J_sc) of 21.49 mA cm⁻² and a fill factor (FF) of 65.9%, whereas the devices based on IDT2Se showed a lower maximum PCE of 9.36%.