First-principles investigation of Mg-based MgAl2X4 (X = S, Se) spinels for optoelectronic and energy harvesting applications

Magnesium-based chalcogenides have emerged as promising candidates for optoelectronic and energy harvesting devices. In this study, we investigate the structural, electronic, optical, elastic, and thermoelectric properties of MgAl2X4 (X = S, Se) using density functional theory (DFT). Structural optimization confirms thermodynamic stability with negative formation energies of − 0.994 eV (MgAl2S4) and − 1.359 eV (MgAl2Se4). The modified Becke-Johnson (mBJ) potential reveals direct band gaps of 2.8 eV for MgAl2S4 and 1.9 eV for MgAl2Se4, suitable for optoelectronic applications. Optical analysis shows strong absorption in the visible–UV range, with absorption coefficients of $$\sim$$ ∼ 50 × 104 cm⁻1 for MgAl2S4 and $$\sim$$ ∼ 60 × 104 cm⁻1 for MgAl2Se4. Elastic constants confirm mechanical stability and ductile behavior, while thermoelectric analysis reveals high Seebeck coefficients and figure of merit (zT) values of 0.96 and 0.95 for MgAl2S4 and MgAl2Se4, respectively. The combination of favorable electronic, optical, and thermoelectric properties underscores the potential of MgAl2X4 chalcogenides for advanced applications in photovoltaics and thermoelectric devices. Graphical abstract Figure (a) shows the absorption coefficient, while Figure (b) presents the figure of merit at 300 K, highlighting the suitability of the materials for optoelectronic and thermoelectric applications.