Synthesis and photovoltaic properties of benzimidazole-based copolymer with fluorine atom

A new accepter unit, 5,6-difluoro-2,2-dimethyl-2H-benzo[d]imidazole, was prepared and utilized for the synthesis of the conjugated polymers containing electron donor-acceptor pair for OPVs. Difluoro-dimethyl-2H-benzoimidazole unit was designed to introduce electron-withdrawing F atom in dimethyl-2H-benzimidazole unit to improve deeper HOMO and higher V (OC) of the polymer. New semiconducting copolymer with dioctyloxybenzodithiophene, as the electron-rich unit, and difluoro-dimethyl-2H-benzoimidazole, as the electron-deficient unit, was synthesized by Stille polymerization.