Comparison of Y_3Al_5O_(12):Ce_(0.05) Phosphor Coating Methods for White Light Emitting Diode on Gallium Nitride

摘要

White light was obtained by mixing blue light from the emission of a GaN chip and yellow light by the fluorescence of a Y_3Al_5O_(12):Ce_(0.05) yellow phosphor. A uniform coating of yellow phosphor on a GaN chip and an optimized thickness of a phosphor layer were necessary for achieving efficient white LED. Several methods for coating yellow phosphor particles such as the slurry method, the settling method, the electrophoretic deposition (EPD), and the modified EPD were examined for preparing the phosphor layer. The properties of the phosphor layer prepared by these methods were examined using SEM, XRD, and photoluminescence. The intensity of white light and the harmony between blue light and yellow light were dependent on the thickness of the phosphor layer. The properties of the phosphor layer made by the EPD such as packing density, thickness and uniformity could be more easily controlled than by the slurry and settling methods. Further weak adhesion strength of phosphor particles by the EPD could be overcome via the use of a UV curable PVA + ADC layer on the phosphor layer in the EPD.