Pressure–temperature driven phase transition and optoelectronic improvement in lead-free hybrid perovskite MASnI3

Abstract

Lead-free hybrid perovskite CH₃NH₃SnI₃ (MASnI₃) is a promising light-absorbing material for optoelectronic energy-relevant optoelectronic applications owing to its favorable electronic properties and reduced environmental impact compared to lead-based counterparts. In this study, we systematically investigate the structural, optical, and electrical evolution of MASnI₃ under combined high-pressure and elevated-temperature conditions. In situ synchrotron X-ray diffraction reveals that MASnI₃ undergoes pressure-induced amorphization at room temperature, whereas concurrent heating and compression drive recrystallization into a stable orthorhombic (Pnma) phase. Post-treatment UV–Vis absorption and electrical resistivity measurements demonstrate pronounced enhancements in both light absorption and electrical conductivity, relative to pristine and room-temperature-processed samples. These improvements may be associated with defect suppression, enhanced crystallinity, and structural reordering involving SnI₆ octahedral tilting in addition to metal–halide bond contraction, which may influence the band structure. Our findings establish high-pressure thermal processing as an effective strategy for providing a structure-guided route for stabilizing and optimizing lead-free halide perovskites for sustainable energy optoelectronics.