Correlations between green luminescence efficiency, intrinsic defects and co-doping Cl and S in ZnO phosphors

First-principles pseudo-potential approach on complete zinc oxide (ZnO), vacant O (ZnO:V_o), vacant Zn (ZnO:V_Zn), interstitial Zn (ZnO:Zn_i), chloride (Cl) and sulfur (S) co-doped defective ZnO (ZnO:ClSV_Zn, ZnO:ClSZn_i) reveal that V_o is a shallow donor dopant which has nothing to do with green emission. V_Zn and Zn_i both induce green emission recombination levels in the gap. When Cl and S co-dope in defective ZnO, they will enhance the green emission luminescence intensity, because they can promote the formations of V_Zn and Zn_i defects.