Synthesis of 2,7-Carbazolenevinylene-Based Copolymers and Characterization of Their Photovoltaic Properties

New electroactive and photoactive conjugated copolymers consisting of alternating 2,7-carbazole and oligothiophene moieties linked by vinylene groups have been developed. Different oligothiophene units have been introduced to study the relationship between the polymer structure and the electronic properties. The resulting copolymers are characterized by UV-vis spectroscopy, size-exclusion chromatography, and thermal and electrochemical analyses. Bulk heterojunction photovoltaic cells from different copolymers and a soluble fullerene derivative, [6,6]-phenyl-C61 butyric acid methyl ester, have been fabricated, and promising preliminary results are obtained. For instance, non-optimized devices using poly(N-(4-octyloxyphenyl)-2,7-carbazolenevinylene-alt-3″,4″-dihexyl-2,2′;5′,2″;5″,2″′;5″′,2″″-quinquethiophenevinylene 1″,1″-dioxide) as an absorbing and hole-carrier semiconductor exhibit power conversion efficiency up to 0.8 % under air mass (AM) 1.5 illumination. These features make 2,7-carbazolenevinylene-based and related polymers attractive candidates for solar-cell applications.