Tailoring Tin-Based Perovskite Interfaces Through Cold Reductive Plasma

Tin-based perovskite solar cells are among the most promising lead-free alternatives to conventional lead halide perovskites, yet their efficiency remains limited by defects resulting in self-p-doping, poor film quality, and instability caused by the oxidation of Sn(II) to Sn(IV). Here, we demonstrate a novel, solvent-free, low-temperature reductive plasma treatment to engineer the surface defects of a tin-based perovskite. By employing a mixed N₂/H₂ (95%/5%) plasma, we achieve efficient passivation of surface defects, enhancing the open-circuit voltage (V_OC) and fill factor (FF) of the corresponding photovoltaic devices and ultimately improving the overall power conversion efficiency (PCE). Photoluminescence (PL) and transient surface photovoltage (trSPV) analyses reveal a strong reduction in non-radiative recombination and improved charge carrier extraction at the perovskite/electron transport layer interface. Density functional theory (DFT) confirms that hydrogen incorporation into the perovskite lattice forms a stable I-H-I bridging motif, mitigating p-doping and supporting the experimental observations. This work introduces reductive plasma as a scalable and solvent-free approach to improve the optoelectronic quality of tin halide perovskites, advancing their potential in sustainable photovoltaic applications.