Suppressing ion migration and electrode corrosion in perovskite solar cells through Nb₂O₅ interface engineering

Ion migration and electrode corrosion limit the operational stability of perovskite solar cells (PSCs), hindering their commercialization. Herein, we demonstrate that Nb₂O₅ films effectively address these challenges when incorporated as buffer layers between the electron transport layer (ETL) and the metal electrode. Electrochemical analysis combined with density functional theory (DFT) calculations reveals that Nb₂O₅ exhibits exceptional corrosion resistance against iodide-induced degradation, effectively blocking bidirectional diffusion of iodide ions and metal atoms. Furthermore, the Nb₂O₅ buffer layer optimizes energy band alignment and interfacial contact, strengthens the built-in electric field, and suppresses non-radiative recombination, enabling efficient electron extraction. As a result of these synergistic effects, the Nb₂O₅ modified PSCs achieve a champion power conversion efficiency (PCE) of 25.85%, with an open-circuit voltage of 1.194 V and a fill factor of 85.35%, significantly outperforming the control device with a PCE of 23.97%. The Nb₂O₅ modified devices demonstrate excellent operational stability. The device retains 94% of its initial PCE after 500 h of maximum power point (MPP) tracking under ambient conditions with 60–65% relative humidity. This cost-effective approach establishes oxide buffer layers as a practical strategy to advance the commercial viability of PSCs, and provides fundamental insights into interface corrosion mechanisms and engineering principles of ETL/electrode interfaces for long-term device stability.