Three‐in‐One Strategy Enables Single‐Component Organic Solar Cells with Record Efficiency and High Stability

Abstract Single‐component organic solar cells (SCOSCs) with covalently bonding donor and acceptor are becoming increasingly attractive because of their superior stability over traditional multicomponent blend organic solar cells (OSCs). Nevertheless, the efficiency of SCOSCs is far behind the state‐of‐the‐art multicomponent OSCs. Herein, by combination of the advantages of three‐component and single‐component devices, this work reports an innovative three‐in‐one strategy to boost the performance of SCOSCs. In this three‐in‐one strategy, three independent components (PM6, D18, and PYIT) are covalently linked together to create a new single‐component active layer based on ternary conjugated block copolymer (TCBC) PM6‐D18‐b‐PYIT by a facile polymerization. Precisely manipulating the component ratios in the polymer chains of PM6‐D18‐b‐PYIT is able to broaden light utilization, promote charge dynamics, optimize, and stabilize film morphology, contributing to the simultaneously enhanced efficiency and stability of the SCOSCs. Ultimately, the PM6‐D18‐b‐PYIT‐based device exhibits a power conversion efficiency (PCE) of 14.89%, which is the highest efficiency of the reported SCOSCs. Thanks to the aggregation restriction of each component and chain entanglement in the three‐in‐one system, the PM6‐D18‐b‐PYIT‐based SCOSC displays significantly higher stability than the corresponding two‐component (PM6‐D18:PYIT) and three‐component (PM6:D18:PYIT). These results demonstrate that the three‐in‐one strategy is facile and promising for developing SCOSCs with superior efficiency and stability.