Hydrogen‐Bonding Interactions Between Terpolymers Enable Excellent Device Efficiency and Operational Stability of Non‐Halogenated Solvent‐Processed Polymer Solar Cells

Abstract Although polymer solar cells (PSCs) have shown considerable power conversion efficiency (PCE) potential, their poor operational stability is a major obstacle for their future commercialization. In this study, the ternary‐blend strategy based on D1–A–D1–D2‐type conjugated random terpolymers containing hydrogen–bonding sites is employed to simultaneously improve device efficiency and long‐term stability. Notably, the PM6‐ThEG:PM6‐ThOH:Y6‐BO ternary‐blend system exhibits a remarkable PCE of 17.2% with superior photo, thermal, and mechanical stability, outperforming those of binary devices based on PM6, PM6‐ThEG, and PM6‐ThOH polymer donors. These outstanding results are likely attributed to the robust molecular lock via hydrogen bonds between PM6‐ThEG and PM6‐ThOH terpolymers, which can induce strong intermolecular packing, a dense 3D terpolymer network, and optimized morphology. These results also correlate well with the computational study. A comprehensive analysis of optoelectronic and morphological properties as well as the exploration of underlying physical mechanisms collectively verifies the effectiveness of this approach based on mixed random terpolymers with hydrogen‐bonding moiety to achieve the non‐halogenated solvent‐processed PSCs with exceptional efficiency and operational stability.