Pressure-guided band gap tuning from the ultraviolet to the visible region and enhancing optoelectronic features of inorganic AMgCl3 (A = Ga, In, and Tl) perovskites

Through first-principles calculations, this work explores structural, mechanical, electronic, and optical characteristics of metal cubic halide perovskites of AMgCl₃ (A = Ga, In, and Tl) under pressure because of the greater range of applications. The obtained lattice constants at 0 GPa are 4.972 Å, 5.022 Å, and 5.030 Å for GaMgCl₃, InMgI₃, and TlMgCl₃, respectively. Furthermore, the bond length and the lattice parameters are decreased by increasing pressures, while the band gaps transfer from the ultraviolet to the visible area. This leads to the performance of optoelectronic devices being enhanced by encouraging the movement of electrons from the valence-to-conduction band. Moreover, GaMgCl₃ and TlMgCl₃ exhibit indirect band gaps, while InMgCl₃ has direct band gaps at ambient pressure. These indirect band gaps convert into direct ones according to applications of positive pressure; at the same time, the other compound band remains direct. Besides, DOS determines the origins or states of conduction and valence bands. Then, utilizing the charge density mapping, the covalent and ionic nature of Mg-Cl and Ga/In/Tl-Cl were investigated with and without pressure. Here, bonding becomes stronger between atoms under pressure, which is consistent with the previously calculated bond length. Additionally, the optical characteristics are enhanced when pressure is applied, especially for absorption, and conductivity notably improves in the visible area. Finally, these materials have greater ductility, stability, and anisotropy, which are improved by applied pressure. These results show that these compounds are promising candidates for optoelectronic devices.