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.