Exploring photocatalytic and photovoltaic applications of chalcogenide Perovskites, ABS3 (A = Li, Na, K, Rb, Cs; B = Si, Ge, Sn): A First-Principles investigation using the HSE-06 hybrid functional

Unlike traditional semiconductors, chalcogenide perovskites offer a unique combination, merging the stability and safety of oxides with the tunability of halide semiconductors, making them particularly promising for photocatalytic and photovoltaic applications. This paper theoretically investigates the optoelectronic properties of the triclinic ABS₃ (A = Li, Na, K, Rb, Cs; B = Si, Ge, Sn) perovskites using density functional theory with the HSE06 hybrid functional. The feasibility of synthesizing ABS₃ materials was revealed using formation energy calculations. Band structure and density of state calculations confirm that all compounds under investigation are semiconductors exhibiting indirect bandgaps. These bandgaps increase with the ionic radius of the A-site cation, following the trend Li < Na < K < Rb < Cs. Additionally, the order of bandgap energies for the B-site elements is observed as Si > Sn > Ge. This trend emphasizes the significant influence of cation size on the electronic properties of perovskite materials. The investigated perovskites exhibit bandgaps between 1.67 and 3.55 eV, with a narrow difference (0.03–0.49 eV) between their indirect and direct gaps. We additionally compute various optical parameters (dielectric function, refractive index, extinction coefficient, optical conductivity, absorption coefficient, reflectivity, and energy loss function) across the 0–50 eV energy range. The valence and conduction band edge potentials of ABS₃ perovskites were calculated to evaluate their potential applications in water splitting, carbon dioxide reduction, and photodegradation processes. The results of this study demonstrate that several ABS₃ semiconductors exhibit promising characteristics that position them as efficient photocatalysts for these photocatalytic reactions. LiGeS₃ and NaGeS₃, in particular, are promising for solar cell applications.