Band gap tuning of non-toxic Sr-based perovskites CsSrX3 (X = Cl, Br) under pressure for improved optoelectronic applications

For technological applications in optoelectronic devices, non-toxic halide perovskite materials' have crucial inherent and enhanced properties. From this perspective, the current article provides a brief summary of the physical characteristics of cubic halide perovskites CsSrX3 (X = Cl, Br), using first-principles theory, which is carried out and evaluated at hydrostatic pressures of zero to 80 GPa. The structural, electrical, optical, mechanical, and elastic anisotropic properties of these compounds are investigated to determine their potential use in optoelectronic sectors. In accordance with previously published data, the lattice parameters and cell volumes demonstrate a decreasing trend when the pressure is increased. The narrowing of the band gaps of the compounds with increasing pressure is carefully explored using band structure and density of states calculations. The wide to narrowing band gaps and the indirect to direct band gaps are considerable phenomena resulting to the use in optoelectronic devices of those materials. Furthermore, it is also observed that the band gap shifted from ultra-violet to visible zone at 80 GPa for both the perovskite materials. The ionic and covalent bonds between Cs-Cl/Br and Sr-Cl/Br are verified, and their lengths are estimated. Most importantly, a higher static dielectric constant, largest absorption spectra in the ultraviolet energy region, and the reflectance of 7.5–18% (bellow 20%) in the visible region is the indication of suitability in optoelectronic devices like UV detectors, anti-reflection coatings in solar panels, OLED, QLED, and waveguides etc. applications under the given pressure conditions. In addition, increased pressure enhances the optical properties, suggesting that they are capable of being employed in the mentioned devices functioning in the visible and ultraviolet spectrums. The study of formation enthalpy, tolerance factor, and Born criteria of CsSrCl3 and CsSrBr3 materials suggested that both are thermodynamically and mechanically stable at specified pressures. Furthermore, hydrostatic pressure retains a crucial impact on the mechanical behavior of semiconductors while holding their stability. Additionally, the calculated hardness and machinability index lead in conventional applications of both perovskites. Besides, the calculation of several anisotropy indices reveals anisotropic nature, and this nature is also presented by 3D contour plots. In conclusion, the overall study of these two non-toxic perovskites can guide the scientific research community in future investigations in the laboratory.