Effect of Different Charcogenophenes in Isoindigo-based Conjugated Copolymer on Photovoltaic Properties

Abstract

New low bandgap conjugated copolymers composed of isoindigo as electron-deficient unit and various chalcogenophenes (thiophene, selenophene and tellurophene) as electron-rich unit were synthesized (as denoted by PIT, PISe and PITe, respectively) to investigate the effect of different chalcogenophene on the photovoltaic properties of isoindigo-based copolymers. The copolymers (PISe and PITe) show bathochromic shift in UV-Vis absorption and lower LUMO energy level as compared to its thiophene analogue (PIT). The solar cell device based on PISe blended with PC61BM exhibits a promising power conversion efficiency (PCE) of 5.72% with a JSC of 10.21 mA cm?2, which is higher than those of PIT (PCE of 3.98% and JSC of 8.34 mA cm?2), while the device based on PITe shows lower JSC and PCE than those of PIT and PISe because of its coarse morphology of the blend.