Burn‐in‐Loss‐Free Organic Solar Cells With Over 2000 h of Thermal Stability Through Nitrone‐Based Interface Passivation

Despite the remarkable advancement of organic solar cells (OSCs) with power conversion efficiencies (PCEs) surpassing 20%, the thermal instability at interfacial layers remains a major obstacle to their practical commercialization. In particular, the molybdenum oxide (MoO x ) hole‐transport layer in inverted OSCs (I‐OSCs) is prone to thermally induced degradation, including work function (WF) shallowing and interfacial diffusion. Although several passivation strategies have been explored to mitigate MoO x instability, their effectiveness remains limited, and the development of advanced passivation materials is still lacking. Here, we report a nitrone‐based passivation strategy using N‐tert‐butyl‐α‐phenylnitrone (PBN). The polar nitrone (N + –O − ) moiety facilitates strong interactions with under‐coordinated molybdenum sites, suppressing both WF shifts and diffusion of MoO x . Notably, comprehensive analyses, including OrbiSIMS depth profiling and drift‐diffusion modeling, reveal that MoO x diffusion, rather than WF shallowing, is the dominant degradation pathway. Consequently, PBN‐passivated devices retain ∼100% of their initial PCE (∼18.1%) after 2000 h at 85°C without a rapid initial PCE drop, known as burn‐in loss. The general applicability of this strategy is further confirmed in PM6:L8BO, PM6:Y6, and PM6:BTP‐eC9 BHJ systems, offering a viable pathway for fabricating robust I‐OSCs.