Theoretical Investigation of the Physical Features of Ternary (Emplectite) CuBiS2 and (Chalcostibite) CuSbS2: Photovoltaic Applications

First-principles evaluations were done to scrutinize the structural, electronic, and optical features of CuBiS₂ and CuSbS₂ ternary alloys. These calculations utilized the FP-LAPW (full potential-linearized augmented plane wave) technique within the framework of the DFT (density functional theory). To accurately model the exchange-correlation potential in total energy computations, the WC-GGA (Wu-Cohen generalized gradient approximation) was employed. For the band structure computations, the improved Becke–Johnson potential approximation has been utilized, which effectively addresses the band-gap underestimation typically seen in standard DFT approaches. The results showed that the calculated lattice constants and band-gap values of these ternary compounds closely match existing theoretical and experimental data. Furthermore, to explore the optical features of emplectite and chalcostibite, calculations were performed for refractive index, the reflectivity, dielectric function and absorption coefficient. The findings from the electronic and optical properties suggest that these ternary compounds could be highly beneficial for applications in photonics and photovoltaics, owing to their favourable characteristics.