First-principles calculations of wurtzite ZnS_1-xSe_x solid solutions for photocatalysis

In this work, the structural, electronic and optical properties of ZnS_1-xSe_x solid solutions in wurtzite phase are calculated by using full potential linearized augmented plane wave method. The GGA, HSE06 and mBJ approximations are used to calculate the bandgap values. The calculated mBJ bandgap values are close to the experimental results, which are 3.61, 3.49, 2.84, 2.72 and 2.60 eV for the compounds ZnS, ZnS_0.75Se_0.25, ZnS_0.5Se_0.5, ZnS_0.25Se_0.75 and ZnSe, respectively. The Zn 4 s, Zn 3p, Zn 3d, S 3p and Se 4p states show prominent contribution to the density of states of ZnS_1-xSe_x solid solutions. The materials show maximum photoresponse in the ultraviolet energy region; while the edges of optical spectra shift to the low energy range with increasing the concentration of Se in the ZnS_1-xSe_x solid solutions. Calculated effective mass is less than 1.5m₀ for all the solid solutions with different Se concentrations, indicating that the ZnS_1-xSe_x solid solutions exhibit high charge mobility. Furthermore, conduction band minimum (CBM) of the ZnS_1−xSe_x lies at a more negative value than the CO₂ reduction potential and valence band maximum (VBM) is more positive than the water oxidation potential. All these suggest that the ZnS_1-xSe_x solid solutions are promising for photocatalysis as the catalysts.