TPD-Based Copolymers with Strong Interchain Aggregation and High Hole Mobility for Efficient Bulk Heterojunction Solar Cells

A–D–A conjugated polymer, PTPD-TVT, containing thienopyrroledione and thiophene–vinylene–thiophene (TVT) units was synthesized as an electron donor for organic photovoltaic devices. It possesses a small bandgap and has excellent coplanarity and high hole mobility. To further enhance the interchain interactions between the polymer chains, a selenophene–vinylene–selenophene (SVS) unit was also introduced and copolymerized to form the PTPD-SVS polymer. Devices made from PTPD-TVT and PTPD-SVS have rather promising power conversion efficiencies (PCEs) of 4.87 and 5.74%, respectively. The higher PCE value for solar cells based on PTPD-SVS was attributed to an enhanced carrier mobility resulting from stronger interchain aggregation in the BHJ active layer. These results show that the incorporation of a vinylene unit in TPD-based polymers is an effective way to reduce the bandgap and thereby improve charge transport for efficient photovoltaic devices.