Ti₃C₂T_x (MXene)-Polystyrene Based Passivation for Perovskite Solar Cells With Enhanced Stability

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) Ti₃C₂T_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.