The Crucial Role of Chlorinated Thiophene Orientation in Conjugated Polymers for Photovoltaic Devices.

Chlorinated conjugated polymers not only show great potential for the realization of highly efficient polymer solar cells (PSCs) but also have simple and high-yield synthetic routes and low-cost raw materials available for their preparation. However, the study of the structure-property relationship of chlorinated polymers is lagging. Now two chlorinated conjugated polymers, PCl(3)BDB-T and PCl(4)BDB-T are investigated. When the polymers were used to fabricate PSCs with the nonfullerene acceptor (IT-4F), surprisingly, the PCl(3)BDB-T:IT-4F-based device exhibited a negligible power conversion efficiency (PCE) of 0.18 %, while the PCl(4)BDB-T:IT-4F-based device showed an outstanding PCE of 12.33 %. These results provide new insight for the rational design and synthesis of novel chlorinated polymer donors for further improving the photovoltaic efficiencies of PSCs.