Refined Shockley–Queisser Framework–Guided Acceptor Design Enables Loss-Aware Bandgap Targeting in Organic Solar Cells

High Resolution Image Download MS PowerPoint Slide Precise bandgap tuning is critical for maximizing the power conversion efficiencies (PCEs) of organic solar cells (OSCs). Here, we refined the Shockley–Queisser model by incorporating sub-bandgap absorption and nonradiative losses, predicting an optimal optical bandgap ( E g ) of ∼1.41 eV for Y-series acceptor-based OSCs, higher than the ideal SQ value of 1.34 eV. Guided by this loss-aware target, we designed and synthesized a new acceptor (YCF3-BO) with CF 3 -terminated core- and branched outer-side chains to achieve the target E g in PM6:YCF3-BO devices. The resulting binary and ternary devices achieved PCEs of 19.8% and 20.2%, respectively. This performance arises from two synergistic effects: tuning E g into the refined optimum window enhances photoluminescence quantum yield and suppresses nonradiative recombination, while branched side chains promote a 3D charge-transport network. Furthermore, PM6:YCF3-BO-based photocathodes operated efficiently in underwater solar hydrogen production. This study establishes a unified framework integrating loss-aware bandgap theory with acceptor design and solid-state packing control for advancing organic photovoltaics.