Impact of Solvent-Induced Surface Restructuring on Charge Carrier Dynamics in DMASnI₃

The development of water-stable Sn-based halide perovskites is highly desirable because of their promising applications in solar-driven photocatalysis and optoelectronics. However, given that Sn-based halide perovskites have only been discovered in recent years, the underlying mechanisms governing their stability in water and charge carrier dynamics are poorly understood. In this study, we have investigated the relationship between environmental stability and photochemical properties of DMASnI₃ (DMA = CH₃NH₂CH₃⁺) crystals in various solvents, including water. Our results reveal that exposure to specific polar solvents induced the formation of protective surface layers, leading to changes in the surface composition and optical properties, including a slight red-shift in the absorption edges. Time-resolved single-particle spectroscopy combined with in situ spectroelectrochemistry further demonstrated that exposure of DMASnI₃ to water containing dissolved oxygen shifted the photoluminescence from green, likely originating from shallow trap states, to red, which is associated with deep trap states. These findings highlight the significance of local surface structures and environmental control in maintaining the structural integrity and photocatalytic performance of tin-based halide perovskites, contributing to developing robust lead-free materials for sustainable applications, such as hydrogen production and environmental remediation.