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

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.