Effects of Cu-X ( X=B, Al, Ga, In) co-dopings on visible light absorption of ZnS
ZnS has been used for splitting water to produce hydrogen, however, the reaction cannot be driven by the visible light because of its wide energy band gap. In order to reduce the band gap of zinc blende ZnS and in-crease the absorption of visible light, the effects of Cu-X ( X=B, Al, Ga, In) co-dopings on the electronic structure and visible light absorption of ZnS were studied by density functional theory ( DFT). Calculation results reveal that the binding energies of Cu-X ( X=B, Al, Ga, In) co-doped ZnS are negative, therefore, these systems are stable. Cu-X ( X=B, Al, Ga, In) co-dopings reduce the band gaps of zinc blende ZnS from 2. 9 eV to 2. 68 eV, 2. 41 eV, 2. 18 eV, and 1. 82 eV, respectively, resulting in red shift of absorption spectrum and light guide, which are beneficial for visible light absorption. Co-dopings shift the bottom of the conduction band toward the lower energy level, and introduce a p-d hybridization level in the forbidden band, resulting in the band gap width decreasing, which are beneficial for the absorption of visible light and the prevention of photo-generated carrier recombination. Moreover, band edge positions of co-doped ZnS are suitable for water split-ting to generate hydrogen, and this implies that Cu-X ( X=B, Al, Ga, In) co-doped ZnS will be candidate materials for water splitting driven by visible light. In general, Cu-X ( X=B, Al, Ga, In) co-doped ZnS are beneficial for the absorption of visible light.
ZnSDensity functional theory ( DFT)Electronic structuresOptical propertiesAcceptor level
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