In situ inorganic passivation strategy for high-performance perovskite solar cells

Perovskite solar cells continue to advance in efficiency, yet their long-term operational stability remains the major obstacle to widespread deployment. Conventional passivation relies heavily on organic molecules, whose weak intra-layer and interfacial interactions make them vulnerable to heat, moisture, and illumination. As these organic layers degrade, they accelerate perovskite decomposition and induce adverse interfacial reactions, ultimately limiting device durability in real-world conditions. Inorganic passivation presents a compelling alternative: its stronger chemical bonding and intrinsic stability offer a more robust barrier against environmental stressors. This work demonstrates an inorganic surface reaction approach in which ammonium chromate forms a stable Pb–O–Cr interfacial layer, strengthening the perovskite surface and mitigating defect-related degradation pathways, thereby significantly improving device stability over extended operation while simultaneously enhancing power conversion efficiency. • In situ reaction forms a robust Pb–O–Cr inorganic passivation layer • Passivation reduces surface defects and induces n-type surface character • Devices retain over 91% of their performance after 2,750 h of operation In situ reaction forms a robust Pb–O–Cr inorganic passivation layer Passivation reduces surface defects and induces n-type surface character Devices retain over 91% of their performance after 2,750 h of operation Organic molecules are widely employed for defect passivation in high-performance perovskite solar cells. However, the organic passivation layers have weak interactions within the layer and at the perovskite interface, making them vulnerable to degradation by heat, moisture, or light, which accelerates perovskite decomposition and harms device stability. By contrast, inorganic passivation layers possess inherent chemical stability and form stronger interfacial bonds, preventing the intrusion of moisture and oxygen. In this work, an inorganic passivation strategy is established via an in situ reaction between ammonium chromate and the perovskite layer, resulting in a robust and durable Pb–O–Cr inorganic interfacial layer. The strong chemical bonding at the interface effectively suppresses perovskite degradation under operational conditions. As a result, inverted perovskite solar cells incorporating this inorganic passivation achieved a power conversion efficiency of 26.3%. Notably, the devices retain over 91% of their initial efficiency after 2,750 h of continuous illumination (AM 1.5G).