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

Abstract

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 V oc of 0.89 V, J sc of 18.8 mA cm −2 , and FF of 62% in comparison with the PCE of 8.0% with V oc of 0.79 V, J sc 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.