Mitigating Reverse‐Bias Degradation in NiO _x ‐Based Perovskite Solar Cells via Molecularly Engineered Ol‐CzRAA Interlayers

ABSTRACT Reverse‐bias instability remains a critical bottleneck for the commercialization of perovskite photovoltaics, yet the buried NiO x /perovskite interface, which is ubiquitous in high‐performance inverted architectures, remains insufficiently understood. Here, we elucidated voltage‐dependent degradation pathways unique to NiO x ‐based perovskite solar cells (PSCs): moderate reverse bias drives the rapid formation of an electrically insulating NiI 2 interlayer together with a Ni–O–Pb intermediate, while higher bias accelerates grain‐boundary collapse within the perovskite absorber. To counter these processes, we design a conjugated oligomer, Ol‐CzRAA , whose carboxyl moieties chelate Ni ≥3+ species to suppress Ni ≥3+ →Ni 2 + reduction and whose rhodanine C═S groups coordinatively passivate under‐coordinated Pb 2+ defects. This dual‐site molecular engineering simultaneously stabilizes interfacial electronic structure and suppresses s redox‐driven degradation. As a result, devices incorporating Ol‐CzRAA exhibit a breakdown voltage increased by nearly two orders of magnitude, retain 83% of their initial efficiency after 100 h at −1 V reverse bias, and maintain 80% after 500 h continuous illumination. With an optimized interlayer, PSCs reach 25.24% PCE with negligible hysteresis. Our findings establish molecularly engineered NiO x /perovskite interfaces as a powerful strategy to mitigate reverse‐bias‐induced electrochemical degradation and to advance the operational robustness of perovskite photovoltaics.