Mitigating Filamentary Conduction with SiN x O y to Enhance Reverse-Bias Stability in Inverted Perovskite Solar Cells

The operational stability of perovskite solar cells (PSCs) against light, heat, and moisture has been substantially improved through defect passivation, additive engineering, interface optimization, and compositional regulation. In contrast, the reverse bias stability of PSCs employing NiO x /SAM hole-selective contacts remains largely unexplored. Here, we report a perhydropolysilazane (PHPS) modified self-assembled monolayer (SAM) that effectively suppresses Ag filament formation and mitigates reverse bias induced degradation. Incorporation of PHPS leads to a slight enhancement in power conversion efficiency while markedly improving device stability under reverse bias. After 380 h of continuous operation at −1.2 V, PHPS-modified devices retain ≈ 84% of their initial efficiency, whereas control devices degrade to ≈ 60%. This work identifies reverse bias instability as a critical reliability issue in NiO x /SAM-based PSCs and demonstrates PHPS modification as an effective strategy to address this challenge.