A Benzoselenadiazole-Based Low Band Gap Polymer: Synthesis and Photovoltaic Application

A novel alternating copolymer with a low band gap ( E g = 1.55 eV), PBDT–DTBSe, based on benzodithiophene (BDT) and benzoselenadiazole (BSe) units with thiophene as a π-conjugated bridge, was synthesized and characterized. When 1,8-diiodooctane was used as a solvent additive to optimize the mixing morphology, the maximum power conversion efficiency reached by a polymer solar cell based on PBDT–DTBSe/PC 70 BM was 5.18%, which was slightly higher than that of the benzothiadiazole (BT)-based analogue (5.01%). These results demonstrated the promising effectiveness of benzoselenadiazole as an electron-deficient unit for the design of the donor–acceptor photovoltaic polymers.