Synergistic Engineering of Side Chains and Backbone Regioregularity of Polymer Acceptors for High‐Performance All‐Polymer Solar Cells with 15.1% Efficiency

Abstract Tuning the aggregation and crystalline properties of polymers is critical for realizing all‐polymer solar cells (all‐PSCs) with optimal blend morphology and high power conversion efficiency (PCE). In this study, a series of polymerized small‐molecule acceptors (PSMAs) is developed to investigate important relationships among their crystalline/aggregation properties, the blend morphology, and the device performance of the resulting all‐PSCs. A series of PSMAs (regiorandom (RRd)‐C12, RRd‐C20, RRd‐C24, regioregular (RRg)‐C20, and RRg‐C24) with simultaneously‐engineered i) side chain lengths of C12, C20, and C24, and ii) backbone regioregularities of RRd and RRg are synthesized to regulate their crystalline/aggregation properties. As a result, the highest PCE of 15.12% is obtained with all‐PSCs based on RRg‐C20 PSMA having regioregular backbone and optimal side chain length, attributed to high PSMA crystallinity and electron mobility as well as optimal blend morphology with a polymer donor. Thus, this study demonstrates the importance of simultaneous engineering of the backbone regioregularity and side‐chain structures of PSMAs to enhance electron mobility, optimize blend morphology and, thus, achieve highly efficient all‐PSCs.