Isomeric Monomer Engineering of Regioregular Polymer Acceptors for Efficient All-Polymer Solar Cells

In this work, three polymerized small-molecule acceptors (PSMAs) (namely, PBTP-alpha, PBTP-beta, and PBTP-m) based on distinct building blocks are developed to investigate the influence of the regioisomerism of terminal group units (TCN-alpha and TCN-beta) on the physicochemical, photoelectric, and photovoltaic properties of PSMAs. Comparative analysis reveals that PBTP-alpha exhibited red-shifted absorption, enhanced intramolecular charge transfer effects, stronger crystallinity, and denser molecular stacking compared to the regioregular PBTP-beta and regiorandom PBTP-m. By utilizing PM6 as the polymer donor, the PBTP-alpha-based all-polymer solar cell (all-PSC) achieves a higher power-conversion efficiency (PCE) of 8.17% compared with that of the PBTP-beta- (5.99%) and PBTP-m-based (6.16%) devices.