Band gap shifting of halide perovskite CsCaBr3 from ultra-violet to visible region under pressure for photovoltaic applications

Throughout this study, the effects of hydrostatic pressure on the physical properties of halide perovskite CsCaBr3 are explored using the density functional theory. The calculated lattice parameters nicely agree with the previous experimental and theoretical reports, but being decreased under pressure as the interatomic distance is reduced. The electronic band gap is significantly reduced from ultra-violet to visible region under pressure, which makes easier to transport electron from valance band to conduction band responsible for enhancing photovoltaic device efficiency. In addition, the transition of band gap nature from indirect to direct is occurred at 40 GPa, which is more suitable for a material to be used in optoelectronic applications. Deep optical analysis suggests the potential applications of titled perovskite in microelectronics, integrated circuits, QLED, OLED, solar cell, waveguides, solar heat reducing materials, and surgical instruments. The elastic constants nicely pursue the Born stability conditions confirming the mechanical stability of CsCaBr3 under entire range of applied pressure, which justify the thermodynamic stability obtained by the negative values of formation enthalpy. The mechanical properties are also significantly affected by external pressure, which make this compound more ductile and anisotropic.