Pressure-induced structural evolution, optical and electronic transitions of nontoxic organometal halide perovskite-based methylammonium tin chloride

Abstract

Hybrid solar cells with organometal halide perovskites have already reached a power conversion efficiency exceeding 22.1%, but their toxic lead component remains a serious concern. Hence, the replacement of lead with nontoxic alternatives, such as tin, has attracted increasing interest. This study investigates the structural and optoelectronic properties of nontoxic perovskite methylammonium tin chloride (MASnCl3, MA: CH3NH3) under pressure. The synchrotron X-ray diffraction experiment shows that the sample transforms from the monoclinic to the triclinic phase and then amorphizes. The tilting and distortion of [SnCl6]4− octahedra are mainly responsible for the bandgap decreasing below 1.0 GPa. Upon further compression, an additional optical absorption peak appears, which is ascribed to the conduction band splitting of the triclinic MASnCl3. The high pressure behavior of MA cations indicates that the interaction between MA cations and [SnCl6]4− octahedra is strengthened. The pressure-induced electrical resistance evolution of MASnCl3 coincides with the structural changes. The intrinsic properties and the stability of nontoxic Sn-based hybrid perovskites provide better understanding and insights into their potential applications in photovoltaics.