Ring‐Locked Polymer Acceptors for All‐Polymer Solar Cells Synthesized via Knoevenagel Polycondensation

Abstract Polymerized small molecule acceptors (PSMAs) have greatly promoted the performance of all‐polymer solar cells (all‐PSCs), but they are generally synthesized via Stille polycondensation, and thus suffer from the drawbacks of high cost, toxicity, and harsh reaction conditions, etc . Here, two new PSMAs named PITBIC‐F and PITBIC‐Cl are synthesized by the metal‐free Knoevenagel polycondensation process catalyzed by Lewis base, both of which exhibit a high degree of polymerization of over 25. Due to the introduction of the ring‐locked structure, both PSMAs exhibit improved photostability. Mixed with the polymer donor PBDB‐T, all‐PSCs devices have been successfully fabricated, but have shown limited device performance due to inferior charge transport and undesired film phase separation.