Ti ₃ C ₂ T _x (MXene)‐Polystyrene Based Passivation for Perovskite Solar Cells With Enhanced Stability

ABSTRACT Perovskite solar cells are the fastest advancing photovoltaic technology, but their long‐term durability remains a major barrier to commercialization. Surface passivation is a promising and straightforward approach to improve the stability of PSCs while enhancing their performance through surface defect modifications. In this work, we develop a novel passivation layer by employing conductive few‐layer two‐dimensional (2D) Ti ₃ C ₂ T _x (MXene) sheets and hydrophobic polystyrene (PS). This passivation layer not only enables improved charge transfer through nanoscale conductive domains, but also displays excellent moisture tolerance for PSCs. As a result, this newly designed passivation enhanced the crystallinity, reduced the surface defects, and improved the charge transports in PSCs. The PSC device fabricated with PS and MXene (PSMX) passivation achieved a power conversion efficiency (PCE) of 20.01%, outperforming the cells with PS‐only passivated perovskite films. Remarkably, unencapsulated PSMX passivated devices preserved more than 93% of their initial PCEs after aging for 30 days in ambient conditions (40%–50% relative humidity), demonstrating excellent operational stability. These results showcase the effectiveness of integrating conductive 2D materials into hydrophobic polymers for surface passivation, offering a practical pathway toward high‐performance and stable PSCs.