Synthesis and Photovoltaic Properties of Polythiophene Incorporating with 3,4‐Difluorothiophene Units

Abstract

AbstractTwo polythiophene derivatives using fluorine atoms and hexyl or hexyloxy group as electron‐withdrawing and donating substituents have been synthesized. The introduction of fluorine atoms to the polythiophene backbones simultaneously lowers the HOMO and narrows the bandgap, and the stronger electron‐donating ability of hexyloxy side chain further reduces the bandgap. As a result, poly[3‐hexylthiophene‐2,5‐diyl‐alt‐3,4‐difluorothiophene] (PHTDFT) shows HOMO and bandgap of −5.31/1.83 eV and poly[3,4‐dihexyloxythiophene‐2,5‐diyl‐alt‐3,4‐difluorothiophene] (PDHOTDFT) shows HOMO and bandgap of −5.14/1.68 eV, both are lower than −4.76/2.02 eV of P3HT. Benefiting from the lower HOMO, PHTDFT:PC61BM (1:1) polymer solar cells obtain a power conversion efficiency of 1.11% and an impressed open‐circuit voltage of 0.79 V under solar illumination AM1.5 (100 mW/cm2).