High-level periodic conjugated terpolymers through AA/BB monomer pair-type terpolymerization improve performance of polymer solar cells

With a growing interest in developing high-performance π-conjugated terpolymers via random terpolymerization, new synthetic approaches resulting in higher-quality terpolymers with improved backbone regularity are needed to help make organic optoelectronic and photovoltaic applications more prosperous. Herein, we report an AA/BB monomer pair-type terpolymerization protocol that renders semi-sequence-controlled (SSC) terpolymers by polymerizing the aperiodically repeating units into the preferentially formed periodic, alternating polymeric block sequences, unlike the conventional random terpolymerization for producing terpolymers with irregular repeating sequences. A close comparison of SSC- and conventional terpolymerization-derived terpolymers indicate detectable differences in the absorption, energetic properties, carrier transport, energy loss, and morphological characteristics. The optimal SSC terpolymer-based polymer solar cells (PSCs) outperform the conventional terpolymerization-derived counterparts in power conversion efficiency (PCE). Moreover, the optimal SSC terpolymer-based PSCs processed by an eco-friendly solvent/additive system also exhibit outstanding PCEs of 16.52 % (small area of 0.041 cm2) and 15.50 % (large area of 1 cm2). To the best our knowledge, it is the highest value among tetrahydrofuran-processed PSCs. This SSC terpolymerization shows considerable promise in synthesizing high-quality in-chain terpolymers with high backbone sequence control without sacrificing their inherent beneficial features, providing high potential for further improving their PSC performances.