A comparative hybrid-DFT study of energy-efficient halide perovskite under hydrostatic pressure

Abstract

To accomplish the primary aim of this research, follow these steps to conduct a thorough computational evaluation by using the Heyd–Scuseria–Ernzerhof (HSE-03) hybrid functional. This analysis will cover the structural, electrical, elastic, mechanical, anisotropic and optical properties of halide perovskite materials CsPbX3 (X = Cl, Br, and I) by applying pressure from 0 to 25 GPa. Under stress, all materials exhibit consistent decrease in lattice parameters and decrease in band-gap up to 25 GPa. To explore the electronic band structure (BS), we have estimated the TDOS (Total Density of States) and EPDOS (Elemental Partial Density of States). To further assess the material's relevance, we calculated several optical properties including absorption I (ω), extinction coefficient k (ω), refractive index n (ω), loss function L (ω), reflectivity R (ω), real part of the dielectric function ε_1 (ω) and the imaginary part ε_2 (ω). The static values of reflectivity R (ω), real part of the dielectric function ε_1 (ω) increases by applying pressure in all materials. With the pressure application, the peak of absorption peak under study perovskites shifts markedly towards higher photon energies. Moreover, its high refractive index, reflectivity and absorption, make it an important element for optoelectronic devices. The structure retains its cubic form and there is no change in phase in all three materials. The materials are stiff, unyielding, and mechanically stable demonstrating elevated resistance to shear stress based on different mechanical and elastic parameters, including Young’s modulus , bulk modulus and shear modulus. The Pugh/Frantsevich ratios, Kleinman’s parameter, Cauchy pressure and Poisson’s ratio, indicate the ductility of materials, metallic bonding characteristics, and resilience under high pressure. Additionally, distinctive anisotropy factors are used to confirm the material's anisotropic properties.