DFT-Based Investigation of Electronic, Optical, and Thermoelectric Properties of TaCu3X4 (X = S, Se, Te) Chalcogenides for Optoelectronic and Energy Applications

In this investigation, the electronic, optical, and thermoelectric (TE) characteristics of the chalcogenide compound TaCu3X4 (X = S, Se, Te) were examined through first-principles calculations employing density functional theory (DFT). The exchange-correlation potential was determined using the generalized gradient approximation Perdew-Burke-Ernzerhof for solids (GGA-PBEsol). Analysis of the band structures indicated the semiconducting nature of all investigated compounds, with direct band gaps measured at 2.4, 2.2, and 2 eV for TaCu3X4 (X = S, Se, Te), respectively. Notably, strong absorption within the visible and low ultraviolet spectra was observed. Optical dispersion analyses, encompassing complex dielectric function, energy loss function, refractive index, extinction coefficient, reflectivity, and optical conductivity, were conducted within the energy range of 0-14 eV, revealing anisotropic polarization across all compounds, making them promising candidates for optoelectronic applications. Furthermore, the transport properties of the chalcogenide compounds were assessed, indicating noteworthy electrical conductivity, electronic thermal conductivity, and Seebeck coefficient, attributable to the majority electron carriers with semiconductor characteristics. Effective masses of electrons and holes were determined through dispersion curve fitting, highlighting promising TE behavior, as evidenced by the calculated figure of merit for TaCu3X4 (X = S, Se, Te), positioning it as a prospective candidate for renewable energy device implementations.