Pressure-induced multi-functional property analysis of lead-free tin based halide perovskites ASnCl3 (A = Ga, In, Tl) for advanced optoelectronic applications†

Abstract

This work examines the structural, electrical, and optical characteristics of lead-free tin-based halide perovskites, ASnCl₃ (A = Ga, In, and Tl), as environmentally friendly substitutes for lead-based perovskites in solar applications. Hydrostatic pressures ranging from 0 to 8 GPa cause all three compounds – GaSnCl₃, InSnCl₃, and TlSnCl₃ – to display a 3D-cubic perovskite structure. When pressure is applied, lattice parameters and unit cell volumes decrease as follows. For GaSnCl₃, they decrease from 5.554 Å and 171.346 A³ to 5.161 Å and 137.515 A³; for InSnCl₃, they are from 5.568 Å and 172.623 A³ to 5.178 Å and 138.891 A³; and for TlSnCl₃, they are from 5.573 Å and 173.146 A³ to 5.184 Å and 139.352 A³. This suggests that the structure is stable under compression. These compound's formation enthalpies attest to their thermodynamic stability over the investigated pressure range. All three Sn-based compounds exhibit a direct bandgap at 0 GPa, and as pressure increases the band gap decreases, which suggests a tunable electronic structure. TlSnCl₃ demonstrates a significant change from semiconductor to metallic behavior at higher pressures. The optical absorption spectra of the materials shift towards longer wavelengths (redshift) as pressure increases, enhancing the light absorption capabilities of these compounds. The compounds exhibit enhanced mechanical stability and ductility with increasing pressure, as indicated by their bulk, shear, and Young's modulus. Poisson's ratio values for these materials are in the range of 0.372 to 0.441 for GaSCl₃, 0.355 to 0.418 for InSnCl₃, and 0.349 to 0.413 for TlSnCl₃, which highlights their ductile nature. GaSnCl₃, InSnBr₃, and TlSnCl₃ exhibit diamagnetic behavior both under normal conditions and with increased pressure. Thermal conductivity and stability are enhanced with increased pressure, making these materials suitable for high-temperature applications. The ability to tune the properties of these compounds through pressure makes them promising candidates for next-generation optoelectronic devices, energy storage, and conversion systems.