Syntheses and characterization of new low-band gap polymers containing 4H-cyclopenta[def]phenanthrene unit and 4,7-di(thien-2-yl)-2H-benzimidazole-2-spirocyclohexane for photovoltaic device

► Synthetic trials for new low-band gap polymers for solar cell. ► Synthetic trials to decrease the band gap of copolymers are successful. ► Synthetic trial to increase solubility on the electron-deficient moiety is successful. ► We show the possibility to find highly soluble new electron-deficient moiety.