The effect of different chalcogenophenes in isoindigo-based conjugated copolymers on photovoltaic properties

New low bandgap conjugated copolymers based on isoindigo and three different chalcogenophenes (thiophene, selenophene and tellurophene) were synthesized (denoted as PIT, PISe and PITe, respectively) to investigate the effect of different chalcogenophenes on their photovoltaic properties. PISe and PITe show lower bandgaps and deeper HOMO energy levels as compared to PIT. The solar cell device based on PISe blended with PC₆₁BM exhibits a promising PCE of 5.72% with a J_SC of 10.21 mA cm⁻², while PITe shows the lowest PCE of 1.16% with the lowest J_SC of 2.51 mA cm⁻² because of its coarse morphology although the field-effect hole mobility of PITe is the highest due to higher crystallinity than others.