Asymmetrically Substituted Quinoxaline Enabling Conformation-Locked Polymer Donors toward High-Performance Polymer Solar Cells

Polymer donors are a key component for high-performance polymer solar cells (PSCs), and the emergence of giant acceptors presents a challenge in designing accessible polymer donors that improve miscibility and device performance. In this study, we developed a series of quinoxaline (Qx)-based polymers by introducing monosubstituted conjugated side chains and employing noncovalent conformational locks to maintain backbone rigidity. This approach minimizes steric hindrance and enhances molecular rigidity while simplifying the synthesis, potentially reducing the cost of Qx-based materials. Among these polymers, F atom-substituted PF-2F demonstrated superior planarity due to CH···F hydrogen bonds, thereby improving crystallinity and miscibility with tethered dimeric acceptors (DY2). As a result, the binary PSC based on PF-2F achieved a PCE of 17.5%, which increased to 18.3% after the addition of additional polymer donor D18 to construct ternary PSCs. This work highlights how conformational locks in asymmetric monosubstituted side chains modulate photovoltaic properties, providing new insights for the rational design of Qx-based donor materials that complement giant acceptors.