Exploration of the Structural, Optoelectronic, Magnetic, and Thermoelectric Properties of Eu Doped LaCuSiSe₇ Chalcogenide for Photovoltaic Applications: First-Principle Study

Density functional theory (DFT) analyzed the structural and electronic characteristics of Cu-based spinel Chalcogenides, LaCuSiSe_7, and [LaCuSiSe₇]: Eu and their thermoelectric and optical properties. The negative spinel formation energy values showed its ferromagnetic phase stability. Band structure optimization and density of states calculations showed that they were ferromagnetic, and semiconducting band structure was observed for both channels. Density-of-states-based exploration of exchange splitting energies allowed us to learn more about the exchange constants ( \({N}_{0\alpha }\) and \({N}_{0\beta }\) ). Larger values of \({N}_{0\beta }\) compared to \({N}_{0\alpha }\) were used to explain the dissociation of Cu/Eu d-states. The strong p-d hybridization shows that the exchange field dominates the crystal field that generates ferromagnetism in these spinels. In addition, the magnetic moment of Cu ions was reduced by p-d hybridization, which diverted some of the moment to nonmagnetic locations. Spinels were also studied for their optical properties, and results showed that they have a low dispersion of light and a refractive index in the visible area, making them promising candidates for optoelectronic applications. [LaCuSiSe₇]: Eu has positive Seebeck coefficients at temperatures between 0 and 800 K, but LaCuSiSe₇ has a negative Seebeck coefficient at higher temperatures. This demonstrates that these Chalcogenides are suitable candidates for optoelectronic and thermoelectric devices.