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

Abstract

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 (MoOx) 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 MoOx 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-alpha-phenylnitrone (PBN). The polar nitrone (N+-O-) moiety facilitates strong interactions with under-coordinated molybdenum sites, suppressing both WF shifts and diffusion of MoOx. Notably, comprehensive analyses, including OrbiSIMS depth profiling and drift-diffusion modeling, reveal that MoOx diffusion, rather than WF shallowing, is the dominant degradation pathway. Consequently, PBN-passivated devices retain similar to 100% of their initial PCE (similar to 18.1%) after 2000 h at 85 degrees 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.