High‐Performance Non‐Fullerene Polymer Solar Cells Based on Fluorine Substituted Wide Bandgap Copolymers Without Extra Treatments

A new wide bandgap conjugated polymer, PFBZ, based on fluorination thienyl conjugated benzodithiophene (BDT-2F) as a donor unit and difluorinated benzotriazole (BTz-2F) as an acceptor unit, was synthesized for non-fullerene polymer solar cells (PSCs) application. Compared with the analogue based on non-fluorinated BDT unit (PBZ), PFBZ shows a lower HOMO level, a similar wide optical bandgap with a higher extinction coefficient, and a slightly higher hole mobility. As a result, without any extra treatments, the PFBZ:ITIC-based device exhibits a higher PCE of 10.4% with Voc of 0.89 V, Jsc of 18.8 mA cm−2, and FF of 62% in comparison with the PCE of 8.0% with Voc of 0.79 V, Jsc of 17.2 mA cm−2, and FF of 59% for PBZ:ITIC-based devices. Furthermore, the photovoltaic performance of the PFBZ: ITIC-based devices are relatively insensitive to the thickness of the active layer and the PCE still remains 8.9% with a thickness of up to 200 nm. In addition, the PFBZ: ITIC-based devices exhibit high tolerance to the thermal annealing, and still show a high PCE of 9.3% with annealing at 150 °C for 1 hour. These results indicate that PFBZ is a promising candidate for the large scale manufacturing and practical application of high efficient PSCs.