Hybrid Density Functional Theory Study on Structural and Optoelectronic Properties of ZnSe1–xTex for the Photocatalytic Applications

In this work, hybrid density functional theory has been used to investigate the structural and optoelectronic properties of wurtzite ZnSe1–xTex solid solutions. The calculated bandgap values are 2.82, 2.60, 2.48, 2.38, and 2.15 eV for the ZnSe, ZnSe0.75Te0.25, ZnSe0.50Te0.50, ZnSe0.25Te0.75, and ZnTe, respectively, which are in agreement with the experimental results. The valence band maximum of ZnSe1–xTex solid solutions is mainly comprised of Se-4p, Te-5p, Zn-3p, and Zn-3d states. Moreover, a red shift (toward longer wavelength) is observed in the absorption edges of the ZnSe1–xTex solid solutions, which enables them to effectively utilize visible light for the photocatalytic applications. The Te doping into ZnSe can increase the n-type conductivity of the obtained solid solutions. Effective mass of photogenerated charge carriers at all Te concentrations is less than 1.5m0, implying the high mobility of charge carriers in the ZnSe1–xTex solid solutions. The charge separation can be improved at the 25% and 50% doping of Te. Moreover, the positions of valence and conduction band edges of ZnSe1–xTex ternary alloys straddle the potentials of both CO2 reduction and water oxidation, implying that these solid solutions are promising for the photocatalytic reduction of CO2 and oxidation of water. In addition, the water and CO2 molecules are strongly adsorbed on the surface of solid solutions.