Pressure-induced modifications in the electronic, mechanical, optical, and thermodynamic properties of CsPbI3 for advanced optoelectronic applications: A DFT study

Abstract

Halide perovskite-based materials have garnered significant attention in the scientific community due to their diverse optoelectronic and photovoltaic applications. This study employed density functional theory (DFT) to investigate the substantial changes in the physical properties of cubic halide perovskite CsPbI₃ under hydrostatic pressures ranging from 0 to 55 GPa. Under high external pressures, CsPbI₃ transitions from semiconducting to metallic, with conduction and valence band maxima convergent at 40 and 55 GPa. The intrinsic structure of CsPbI₃ exhibits direct band gap tuning at the Γ point, decreasing with pressure and reaching optimal photoelectric efficiency values (1.30–1.40 eV) within the 35–45 GPa range. Bandgap modifications alter state density, impacting conduction and valence band contributions. The mechanical response of CsPbI₃ shows its ductile behavior and ability to improve properties under external pressure. Elastic coefficients increase at a maximum pressure value, indicating stiffness and resistance to shear deformation. However, when pressure exceeds 45 GPa, the phenomenon of phase stability sharply breaks down. Furthermore, dynamic dielectric functions are often used to measure the impact of band gap reduction on optical properties and illustrate that the pressure increases lead to a rise in the behavior of static refractive index. The optical absorption peak of CsPbI₃ exhibits a redshift with growing pressure, attributed bandgap reduction, and demonstrates enhanced light absorption and conductivity. The thermodynamic analysis examines phonon dispersion, lattice vibrations, and thermal conductivity. The results show structural stability under pressures from 0 to 45 Pa, highlighting CsPbI₃’s suitability for heat-dissipating applications. These findings suggest that CsPbI₃ has significant potential for advanced optoelectronic applications, particularly in the development of efficient photovoltaic materials that leverage its unique properties under pressure.