An axisymmetric heptacyclic lactam unit for efficient polymer solar cells

Abstract

An axisymmetric heptacyclic lactam unit TD3 has been developed by replacing the thieno[3,2-b]thiophene core of a known acceptor unit TD1 with dithieno[3,2-b:2′,3′-d]thiophene. PThTD3 was obtained by copolymerizing TD3 with thiophene in good yield. PThTD3 showed red-shifted absorption, lower LUMO energy level, and better hole mobility relative to the analogue PThTD1. Inverted polymer solar cells based on PThTD3:PC₇₁BM exhibited a decent PCE of 7.25%, which is much higher than that of PThTD1. These results have demonstrated that axisymmetric lactam TD3 is a good building block for PSC applications.