Bandgap tuning of RbCaBr3 using hydrostatic pressure: First-principles insight to explore its electronic, physical, thermophysical, and mechanical properties

Abstract

Halide perovskites are a very important class of material in solar cell fabrication. In this study, the properties of lead-free halide perovskite RbCaBr₃ explored under hydrostatic pressure 0–120 GPa. To study the characteristics of the RbCaBr₃ perovskite solar cell, first-principles density functional theory (FP-DFT) simulations with the Cambridge Serial Total Energy Package (CASTEP) formulation were used. At 40 GPa pressure, the materials show a direct bandgap at the Gamma point while 0 GPa shows an indirect bandgap. As the pressure increases, the bandgap varies from 4.22 eV to 0.227 eV. Mulliken population analysis and density of states curves have been used to investigate the bonding nature. These parameters indicate the presence of ionic bonding. Pressure increases certain thermophysical parameters, such as the melting and Debye temperatures. According to the Born-Huang criterion, the mechanical stability of RbCaBr₃ has been confirmed. The values of Cauchy's pressure, Pugh's ratio, and Poisson's ratio indicate the ductile nature of RbCaBr₃. The computed elastic parameters suggest reasonably high machinability and isotropic behavior, which are important for practical applications in various fields. Based on its large range of direct bandgap, stability, and other properties, RbCaBr₃ is a potential material for optoelectronics and solar cell research.