First-principles calculations of optoelectronic and thermoelectric properties of semiconducting germanium chalcogenide

This work explores the optoelectronic properties of CdAg₂GeS₄ and Ag₂GeS₃ compounds through the TB-mBJ approximation implemented in the Wien2k software and accessory code BoltzTraP. The electronic profile shows that both compounds have a semiconductor character with a narrow bandgap, which is important for thermoelectric devices. For both compounds, further analyses of the complex dielectric constant ε(ω), refractive index n(ω), reflectivity R(ω), absorption α(ω), and optical conductivity σ(ω) have been reported. We calculated the thermoelectric properties of Ag₂GeS₃ compound, such as variation of Seebeck coefficient, power factor, thermal and electrical conductivity. Ag₂GeS₃ is an n-type semiconductor and it exhibits ultra-low glass-like lattice thermal conductivity.