Pressure-Induced Enhanced Optical Absorption in Sulvanite Compound Cu 3 TaX 4 (X = S, Se, and Te): An ab Initio Study.

Ab initio study on the family of ternary copper chalcogenides Cu 3 TaX 4 (X = S, Se, and Te) is performed to investigate the suitability of these compounds to applications as photovoltaic absorber materials. The density functional theory based full potential linearized augmented plane wave method (FP-LAPW method) is employed for computational purposes. The electronic structure and optical properties are determined including electron-electron interaction and spin-orbit coupling (SOC), within the generalized gradient approximation plus Hubbard U (GGA+ U ) and GGA+ U +SOC approximation. The large optical band gaps of Cu 3 TaS 4 and Cu 3 TaSe 4 considered ineffective for absorber materials, and also the hole effective mass has been modulated through applied pressure. These materials show extreme resistance to external pressure, and are found to be stable up to a pressure range of 10 GPa, investigated using phonon dispersion calculations. The observed optical properties and the absorption coefficients within the visible-light spectrum make these compounds promising materials for photovoltaic applications. The calculated energy and optical band gaps are consistent with the available literature and are compared with the experimental results where available.