Impact of Applied Pressure on Tin-Based Cubic Halide Perovskite ASnX3 (A = Li, Na and X = Cl, Br, and I) in Reference to Their Optoelectronic Applications

Semiconductor behavior has emerged as a promising substance for numerous advancements in natural energy production, storage, and conversion, as well as in medical technology due to exceptional properties and capabilities of the perovskites. Additionally, this property also presents a great opportunity for solar cells to serve as a substitute for conventional silicon-based photovoltaic systems, as they provide greater efficiency and cost-effective conversion of sunlight to electricity. Here, we are for the first time investigating lead-free environment-friendly cubic perovskites ASnX(3) (A = Na and Li; X = Cl, Br, and I) under different hydrostatic pressures ranging from 0 to 5 GPa. Utilizing the GGA + PBE functional method with a space group of 221 (Pm3m), ASnX(3) compounds (A = Na and Li; X = Cl, Br, and I) demonstrate direct bandgaps at 0 GPa, ranging from 0.790 to 0.282 eV for Li-based halides and 0.760-0.296 eV for Na-based halides, characterizing their semiconductor nature within the perovskite crystal lattice. Furthermore, our analysis revealed that the conduction band and the valence band intersect at a point above the Fermi level which influences the transition of semiconductor to metal or the creation of a half-metallic state. The optical and structural properties of the compound were also examined, and as the pressure rose from 0 to 5 GPa, the absorption redshift occurred. The analysis of magnetic properties revealed that ASnX(3) (A = Na and Li; X = Cl, Br, and I) compounds have diamagnetic behavior in both normal and under pressure conditions. Meanwhile, compounds that satisfy mechanical stability requirements up to certain pressures demonstrate alternations in bulk modulus, shear modulus, and Young's modulus. The compounds show ductile behavior as their Poisson's ratio values range between 0.28 and 0.44 for every compound. Increasing pressure increases the values of the compounds, but the compounds remain in the same range of ductile material and show better ductility. Finally, increasing pressure influences the characteristics of the compounds as I-based compounds change phase transitions from semiconductor behavior to metallic behavior. On the other hand, Cl-based and Br-based compounds show semimetallic behavior for increased pressure.