First principles quantum analysis of structural, electronic, optical and thermoelectric properties of XCu2GeQ4 (X = Ba, Sr and Q = S, Se) for energy applications

Cu-based chalcogenide materials have attracted a great deal of attention due to their promising optoelectronic properties. The density functional theory (DFT) framework is used in order to estimate the optical and electronic properties of XCu(2)GeQ(4) (X = Ba, Sr and Q = S, Se). We report the optical and electronic properties of Cu-based chalcogenides in this study, which have narrow and direct bandgap materials. The calculated energy bandgap of quaternary chalcogenide materials decreases in the following sequence: SrCu2GeS4 (0.697 eV), BaCu2GeS4 (0.667 eV), BaCu2GeSe4 (0.378 eV), and SrCu2GeSe4 (0.195 eV). This reduction in energy bandgaps shows significant effect of changing dopants on electronic and consequently optical properties of XCu(2)GeQ(4) (X = Ba, Sr and Q = S, Se). The optical characteristics of these materials are investigated in order to explore their potential for optoelectronic applications. However, other materials are emerging as contenders for solar cells, which operate from UV to infrared regions. Initially in infrared region, we can note a redshift in the maximum absorption of incident photons from epsilon(2)(omega)plots in the following sequence: BaCu2GeS4 (1.52 eV), SrCu2GeS4 (1.50 eV), BaCu2GeSe4 (1.30 eV), and SrCu2GeSe4 (0.93 eV). The approximated values of reflectivity, R(omega) are plotted against incident photon energy from 0 to14 eV. Thus, the reflectivity is approximately below 50% before E approximate to 12.0 eV and then increased to 70% reflection at similar to 13.0 eV. Based on calculated thermoelectric properties, these chalcogenides are promising thermoelectric materials. The ZT values of XCu(2)GeQ(4) (X = Ba, Sr and Q = S, Se) decreased in the following sequence: SrCu2GeSe4 (2.6), BaCu2GeSe4 (1.85), SrCu2GeS4 (1.01) and BaCu2GeS4 (0.94). Hence, we believe our findings propose promising materials for anti-reflecting coating layers in optoelectronic technology.