Luminescence characterization of (Ca1−xZnx)Ga2S4:Eu2+ phosphors for a white light-emitting diode

We investigated the luminescence properties of (Ca1−xZnx)Ga2S4:Eu2+ phosphor as a function of Zn2+ and Eu2+ concentrations. The luminescence intensity was markedly enhanced by increasing the mole fraction of Zn2+ at Ca2+ sites. Lacking any Zn2+ ions, CaGa2S4:0.01Eu2+ converted only 18.1% of the absorbed blue light into luminescence. As the Zn2+ concentration increased, the quantum yield increased and reached a maximum of 24.4% at x = 0.1. Furthermore, to fabricate the device, the optimized green-yellow (Ca0.9Zn0.1)Ga2S4:Eu2+ phosphor was coated with MgO. White light was generated by combining the MgO-coated phosphor and the blue emission from a GaN chip.