Benzobis(silolothiophene)-Based Low Bandgap Polymers for Efficient Polymer Solar Cells

A new type of benzobis(silolothiophene)-based low band gap copolymers PBSTBT and PBSTDTBT were developed via a facile synthetic method in high yield. The introduction of silicon atoms in the large fused rings provides new polymers with low HOMO levels and high hole mobilities up to 0.01 cm2 V−1 s−1. The results from preliminary characterization of bulk heterojuction solar cells showed PCE above 3.5% for both PBSTBT and PBSTDTBT.