Highly enhanced luminescence of ZnO green phosphors by calcining ZnS with NH4Br as additive

Zinc oxide (ZnO) phosphors with highly efficient green emission have been prepared by calcining ZnS with NH4Br as additive in air atmosphere. The luminescent properties of as-prepared ZnO phosphors were characterized by X-ray photoelectron spectroscopy and photoluminescence. Our results reveal that the green emission is ascribed to a transition of a photo-generated electron from the localized defect centers (Vo+) to a deeply trapped hole (VZn−) within the band gap. The addition of NH4Br enhances the luminescent emission of ZnO by promoting the formation of vacancies of both oxygen and zinc.