The effect of thieno[3,2-b]thiophene on the absorption, charge mobility and photovoltaic performance of diketopyrrolopyrrole-based low bandgap conjugated polymers

A series of two-dimensional diketopyrrolopyrrole-based low band gap conjugated polymers were synthesized. Replacing thiophene with thieno[3,2-b]thiophene in the side chain and bridge resulted in significant changes to the optical, electrochemical, and morphological properties of the polymers, as well as the subsequent performance of devices made from these materials. The polymer with thieno[3,2-b]thiophene as a bridge instead of a side chain exhibited an increased absorption coefficient and hole mobility, and resulted in the highest power conversion efficiency (5.34%) in this series of polymers. This finding provides valuable insight for the development of more efficient low band-gap polymers.