Beyond acceptor emissivity: interfacial excited-state energetics and dynamic disorder regulate nonradiative voltage losses for organic solar cells

Abstract Suppressing non-radiative energy loss (ΔEnr) is critical for achieving high open-circuit voltage (VOC) in organic solar cells (OSCs), yet it remains unclear whether intrinsic emissive properties of acceptors can reliably predict voltage losses. Here, we report a counterintuitive phenomenon in which a low-emissive acceptor (D6) delivers a significantly reduced ΔEnr compared with the benchmark L8-BO when blended with D18. Despite lower intrinsic emissivity of D6, the D18: D6 system exhibits a markedly higher electroluminescence efficiency and a reduced ΔEnr of 0.153 eV, leading to an enhanced VOC of 0.980 V. Incorporation of D6 into the D18: L8-BO host yields a ternary device with a power conversion efficiency of 21.01%. Sensitive EQE analysis reveals that favorable CT-state energetics partially contribute to the reduced non-radiative loss of D18: D6, while temperature-dependent photoluminescence analysis further identifies suppressed interfacial dynamic disorder as a critical additional factor. While dynamic disorder is significantly increased in the D18: L8-BO blend, it is effectively suppressed in the D18: D6 system, resulting in preserved emissive interfacial states. Complementary structural and kinetic studies demonstrate that D6 modulates aggregation pathways and stabilizes nanoscale morphology, enabling efficient charge transport and reduced recombination. Furthermore, the beneficial role of D6 can be extended to multiple high-performance acceptor systems, demonstrating its general applicability as an interfacial regulator for improving photovoltaic performance. These results highlight that non-radiative voltage loss in OSCs is governed by the interplay between interfacial excited-state energetics and dynamic disorder rather than by the intrinsic emissivity of the acceptor alone, providing new insights into the design of low-energy-loss photovoltaic materials.