Multi-functional lead-free Ba2XSbO6 (X = Al, Ga) double perovskites with direct bandgaps for photocatalytic and thermoelectric applications: A first principles study

In this paper, the structural formability, electronic, optical, and thermoelectric properties of Ba2XSbO6 (X = Al, Ga) double perovskite oxides are investigated with density functional theory (DFT). Based on our calculations, by considering dynamic stability, energetic stability, the (τ)-tolerance and the (μ)-octahedral factors, both Ba2AlSbO6 and Ba2GaSbO6 double perovskites show perfectly cubic structures with space group Fm-3 m (space group no: 225). Our calculations revealed that Ba2AlSbO6 and Ba2GaSbO6 are semiconductors with direct bandgaps of about 2.87 and 1.86 eV. As a direct bandgap semiconductor with tunable electronic and optical properties, it has been found that these materials are promising candidates for use in water splitting. Furthermore, optical properties investigation has represented remarkable optical properties as they exhibit good absorption coefficients in the visible region of the spectrum. Moreover, we investigated the effect of hydrostatic pressure in the 0–8 GPa range on the compounds' electronic properties and discovered that stress increases the bandgap of the materials while their band gaps remain direct. Finally, our study on the thermoelectric characteristics of Ba2AlSbO6 and Ba2GaSbO6 indicates that they have good Seebeck coefficients and thermoelectric power factors, making them promising thermoelectric materials. The obtained tunable moderate bandgaps, good optical absorption in the visible light region, and high power factors suggest the double perovskite materials for use in different electronic, optical and thermoelectric applications, especially in new energy production applications.