Design and synthesis of benzothiadiazole–oligothiophene polymers for organic solar cell applications

A series of p-type copolymers based on oligothiophene and benzothiadiazole units was synthesised via Stille coupling and their physical, electrochemical and photovoltaic properties were evaluated. The polymers varied in the number and type of oligothiophene units as well as in the position of the solubilizing alkyl chains relative to the benzothiadiazole unit. These differences in the polymer structure had a significant impact on the thin-film transistor mobility and the solar cell power conversion efficiency, thus illustrating the importance of these design factors for polymers in optoelectronic applications.