Unveiling the physical properties of AlMgX3 (X = Cl and I) for emerging energy applications.

In this study, we employed first-principles density functional theory (DFT) to investigate the structural, elastic, optoelectronic, and thermoelectric properties of lead-free halide perovskites, AlMgX3 (X = Cl and I), for renewable energy applications. AlMgX3 exhibit an energetically favourable nature due to their lower formation energy (-4.17 eV per f.u.). Additionally, AlMgX3 are mechanically favourable with high elastic constants. We found that AlMgI3 exhibits higher ductility (B/G = 2.97) and anisotropy. Furthermore, AlMgX3 remain stable at room temperature, as confirmed by AIMD simulations. Both AlMgX3 exhibit a semiconducting nature. Interestingly, a direct band gap (3.60 eV) is observed for AlMgCl3, which could be promising for optical devices. Moreover, AlMgI3 demonstrates superior absorption in the visible spectrum, attributed to its reduced band gap, and exhibits a higher static dielectric constant, which could be beneficial for photovoltaic applications. Furthermore, AlMgI3 achieves a higher figure of merit (ZT = 0.61 at 300 K) due to enhanced electrical conductivity and power factor, though its indirect gap limits its high-temperature performance compared to AlMgCl3 (ZT = 0.70 at 800 K). Moreover, the suitable band edges make them promising for water splitting. These results underscore the suitability of AlMgX3 for a wide range of applications such as solar cells, optoelectronics, thermoelectrics and photocatalysis.