Structural, electronic, optical, thermoelectric, and thermodynamic properties of XIn₂M₄ (X = Cd, Zn; M = S, Se, Te) spinels for solar cell and thermoelectric devices: first-principles study

Abstract In this paper, the structural, electronic, and optical properties of XIn 2 M 4 compounds (X = Cd, Zn; M = S, Se, Te), along with thermoelectric and thermodynamic characteristics are studied based on Density Functional Theory (DFT) implemented in wien2k simulation program. Band structure calculations, using the modified Becke–Johnson potential (TB-mBJ), indicate that CdIn 2 S 4 and ZnIn 2 S 4 compounds exhibited indirect band gaps of 2.294 eV and 2.240 eV, respectively. Substituting S with Se and Te lowered the indirect band gap values of XIn 2 S 4 to 1.565 eV, 1.606 eV, 0.277 eV, and 0.219 eV for CdIn 2 Se 4 , ZnIn 2 Se 4 , CdIn 2 Te 4 , and ZnIn 2 Te 4 , respectively. Additionally, the compounds demonstrated high absorption in the UV-Visible region. All the studied compounds showed an excellent structural and thermodynamic stability, as indicated by their negative formation energies. Thermoelectric properties are investigated via Boltzmann transport theory. The observed range of the figure of merit, which spans from 0.725 to 0.803 at 300K, serves as evidence that these materials exhibit favorable qualities for thermoelectric applications. Moreover, this behavior not only underscores the potential of the investigated materials but also positions them as promising contenders for utilization in visible-light solar cell devices.