Sayeef Shahrear, Md Shah Nawaz Romel, Istiak Ahmed Ovi, Md Muneef Hasan, Fahmida Rubaiya, Md Shahidul Islam
ABSTRACT The work demonstrates a first‐principle study on the properties of lead‐free cubic Ca 3 BiI 3 perovskite applying hydrostatic pressure up to 20 GPa in the DFT framework. The findings verify that Ca 3 BiI 3 maintains its cubic symmetry and structural stability over the range of pressures with periodic decreasing lattice constants, bond lengths, and volumes, which all indicate increases in structural compactness. Electronic examination demonstrates a compression of the direct band gap in 1.265 eV down to 0.100 eV using GGA‐PBE functional indicating a sign of a semiconductor‐metal transition that allows adjustable optoelectronic behavior. Mechanical analysis shows that the compound is stiffer and more ductile under compression. The phonon dispersion is obtained, and it is free of imaginary frequencies and confirms the dynamic stability at the ambient conditions. Optical measurements indicate a good interaction of light and matter and pressure‐increased thermal transport characteristics, which is evidenced by the increase of sound velocities and Debye temperatures. In addition, simulations of the devices with different monolayers of charge transport revealed that ITO/TiO 2 /Ca 3 BiI 3 /CuI/Au was the most ideal combination with a power conversion efficiency of 25.09%. The results demonstrate Ca 3 BiI 3 to be an environmentally clean and pressure‐tunable perovskite to be used in the next generation of photovoltaic and optoelectronic applications.