Surface modification of KBaBP₂O₈:Eu³⁺ phosphors by Al-doped ZnO coating

Abstract KBaBP₂O₈:Eu³⁺ phosphors for white light-emitting diodes (w-LEDs) were prepared by high temperature solid-state reaction. Surface modification of these phosphors was carried out by coating transparent conductive films of Al-doped ZnO (AZO) through a sol-gel method. Phase compositions, morphologies, photoluminescence spectra and zeta potential of KBaBP₂O₈:Eu³⁺ phosphors were examined before and after AZO coating. It was found that surface modification with appropriate AZO coating led to an increase in the luminance intensity but a decrease in the zeta potential of the phosphors dispersed in deionized water. The thermal stability was studied by the temperature dependent photoluminescence spectra for temperature ranging from 30 to 250 C. The AZO-coated phosphors have a superior thermal quenching property compared to the pristine ones. It is thus believed that coating with a transparent conductive AZO film is an effective way to reduce the surface charge buildup and to enhance the thermal stability of phosphors.