Synthesis of an alternating thienylenevinylene–benzothiadiazole copolymer with high hole mobility for use in organic solar cells

A new thienylenevinylene–benzothiadiazole copolymer, poly{1,2-(E)-bis[2-(5-bromo-3-dodecyl-2-thienyl)-5-thienyl]ethene-2,1,3-benzothiadiazole} (PETVTBT), was synthesized and characterized for potential use in solar cells. The polymer had broad absorption over the entire visible region and a low band gap of 1.57 eV. In addition, the polymer had a relatively low HOMO level of about 5.1 eV. Although PETVTBT was a donor–acceptor-type copolymer, the hole mobility reached 0.025 cm2/V s using field-effect transistors. Bulk-heterojunction solar cells that used a PETVTBT:PC[71]BM blend as the active layer showed a power conversion efficiency of 1.0% under a simulated AM 1.5 G solar irradiation at 100 mW/cm2.