Electronic Structure and Photocatalytic Water-Splitting Properties of Ag2ZnSn(S1-xSex)4

The silver-based quaternary chalcogenides have potential applications in solar cell absorbers and photocatalytic water splitting to produce hydrogen. In the present work, the electronic structures and photocatalytic properties of Ag2ZnSn(S1-xSex)4 (x = 0-1) were investigated by the combination of GGA+U and hybrid functional methods. The results indicate that Ag2ZnSnS4 (x = 0) and Ag2ZnSnSe4 (x = 1) have a dispersive conduction band and small electron effective masses, which are beneficial to the photogenerated carrier separation. The hole effective masses are remarkably direction dependent, and that along the [100] and [010] directions are sensitive to strain, which indicates easy modulation of photocatalytic properties. In addition, the band gaps of the Ag2ZnSn(S1-xSex)(4) solid solution can be tuned continuously by controlling the x component, which indicates the easy manipulation of light response range. The transfer abilities of charge carriers can also be improved with increasing Se incorporation. In addition, our results strongly suggest that the proper superlattice structures can be an efficient photocatalytic material for water splitting. The present work can serve as guidance for preparing efficient photocatalytic materials.