Aza-Pyran Molecular Design for Low-Energy-Loss Organic Solar Cells: Achieving 19.86% Efficiency via Energetic Disorder Regulation

• • The aza-pyran acceptor D10, when incorporated as a guest in PM6:L8-BO ternary devices, achieves a power conversion efficiency of 19.86% with a high open-circuit voltage of 0.89 V, representing a significant improvement over binary counterparts and underscoring its potential for commercial viability. • • Non-radiative energy loss is reduced to ΔE3 ≈ 0.23 eV, with an electroluminescence quantum efficiency of ~1.17 × 10-4, directly addressing the trade-off between high JSC and low VOC that has historically limited organic solar cell performance. • • Energetic disorder is lowered to an Urbach energy of 25 meV in ternary blends, indicating more ordered molecular packing and reduced trap states, which is critical for minimizing charge recombination and enhancing fill factor. • • GIWAXS and charge-transport measurements reveal enlarged crystalline domains and more ordered π-π stacking, leading to balanced carrier transport and suppressed recombination—key factors for achieving high fill factors and long-term operational stability in scalable devices.