Compositional Tuning of Barium Titanium Trisulphide-Based Perovskite Chalcogenides: Manganese and Selenium...

The family of transition metal chalcogenides, particularly barium titanium trisulphide ( $\text{BaTi}{S}_3$ ), is one of the classes of materials that have garnered a lot of interest recently, owing to their unique combination of structural versatility, environmental stability, and tunable electronic properties. However, controlled doping of these materials, as is necessary for customizing their electrical and electronic properties, is one of the several challenges still being faced by researchers. Studies on dopant incorporation processes on these materials are yet to be comprehensively determined. In this research paper, two new materials ( ${\mathrm{BaTi}}_{0.5}{\mathrm{Mn}}_{0.5}{S}_3$ and ${\mathrm{BaTi}}_{0.5}{\mathrm{Mn}}_{0.5}{\mathrm{Se}}_3$ ) were modelled from the $\text{BaTi}{S}_3$ and their electronic and transport properties investigated using density functional theory calculations as implemented in the Quantum Espresso package. The Perdew-Burke-Ernzerhof exchange-correlation functional was utilized. It was found out that the substitution resulted in lowering the electrical conductivities, carrier mobilities, and formation energies compared to the original sample, while their densities increased. The results also pointed to the adjustment of the materials' band gaps from 0.71 eV for the original sample to as low as 0.312 eV in the ${\mathrm{BaTi}}_{0.5}{\mathrm{Mn}}_{0.5}{\mathrm{Se}}_3$ sample. Regardless of the changes, the Hall coefficients of the samples turned out to be p-type, whose values increased with the substitutions. The above findings underline the significance of compositional adjustment in maximizing the performance of $\text{BaTi}{S}_3$ and its derivatives in photovoltaic, thermoelectric, and sensor applications.