Computational insights into the structural, electronic, and optoelectronic properties of Sr₂MgXO₆ (X = S, Se) double perovskites: promising candidates for photovoltaic and optoelectronic applications

This research paper explores the structural stability, electronic properties, and optical properties of Sr₂MgXO₆ (X = S, Se) double perovskite oxides using density functional theory calculations. The positive phonon frequencies affirm the dynamical stability, whereas the negative values of formation energy confirm the thermodynamic stability. Moreover, the tolerance/octahedral factor of value 0.94/0.42 for Sr₂MgSO₆ and 0.91/0.44 for Sr₂MgSeO₆ verify their stability in cubic double perovskites structure. The analysis of mechanical properties and elastic constants highlights their anisotropic nature and decent mechanical stability. This study unveils that Sr₂MgSO₆ and Sr₂MgSeO₆ possess p-type semiconducting behavior with direct band gaps of approximately 1.01 eV and 1.29 eV, respectively. Notably, substituting S with Se leads to an increase in the band gap value. The maximum values of the absorption coefficient were calculated as 13.65 × 10⁴ cm⁻¹ for Sr₂MgSO₆ and 15.69 × 10⁴ cm⁻¹ for Sr₂MgSeO₆. The spectroscopic limited maximum efficiency was found to increase with the thickness. As direct band gap semiconductors with tunable electronic and optical properties, these materials are considered strong candidates for use in photovoltaic and optoelectronic applications.