First-principles calculations to investigate switching from semiconducting to metallic with enhanced mechanical and optoelectronic properties of CsPbCl3 under pressure

Lead-free halide perovskites have received increasing attention from the research community due to their various applications in scientific and engineering disciplines. The semiconducting perovskite halide CsPbCl is one of the most promising candidates for constructing photovoltaic and optoelectronic devices. From this perspective, density functional theory is employed in this study to investigate the structural, mechanical, electronic, and optical properties of this perovskite under different hydrostatic pressures ranging from 0 to 20 GPa. The lattice constant (5.732 and 5.047 Å at 0 and 20 GPa pressure, respectively) and unit cell volume (188.33 and 128.57 Å at 0 and 20 GPa pressure, respectively) are significantly reduced due to the pressure effect, while the phase stability is maintained. The mechanical properties of CsPbCl reflect its ductile nature, which has an increasing affinity with pressure. The decreasing tendency of the band gap is also observed at pressure values up to 16 GPa, however, the transformation from semiconducting to metallic behavior occurs at 20 GPa pressure. The tuning of the band gap is responsible for enhancing electron transfer from the valence band to the conduction band, which increases the optical absorption and conductivity, thus making the compound more advantageous for optoelectronic device applications. The overall analysis of optical functions in this study suggests some feasible applications of CsPbCl under pressure.