Efficient non-fullerene polymer solar cells based on a wide bandgap polymer of: Meta -alkoxy-phenyl-substituted benzodithiophene and difluorobenzotriazole

A new conjugated polymer (PBFZ-OP) based on meta-alkoxy-phenyl-substituted benzodithiophene (BDT-m-OP) and difluorobenzotriazole (FBTZ) was designed and synthesized for application as a donor material in non-fullerene polymer solar cells (PSCs). The polymer exhibits a strong absorption in the range of 300-620 nm with a wide bandgap of 1.99 eV, which is complementary to that of the small molecule acceptor ITIC. Meanwhile, it also possesses a deeper HOMO energy level of -5.33 eV and a higher hole mobility of 7.28 × 10^-4 cm² V^-1 s^-1. The PSCs based on PBFZ-OP:ITIC showed a higher power conversion efficiency (PCE) of 10.5% with a V_oc of 0.91 V, J_sc of 18.7 mA cm^-2, and FF of 61.8% in comparison with the PCE of 5.5% with a V_oc of 0.73 V, J_sc of 13.1 mA cm^-2, and FF of 57.8% for J52-based PSCs. The results indicate that PBFZ-OP is a promising wide bandgap polymer donor for the photovoltaic application in non-fullerene PSCs.