Synthesis and photoluminescence properties of Eu~(2+) doped CaS and SrS phosphor for phosphor converted white light emitting diodes

摘要

We have synthesized Eu~(2+) doped CaS red emitting and SrS orange emitting phosphors by carbo-thermal reduction method. The phase purity and surface morphology of prepared material was investigated by using X-ray diffraction (XRD) and Scanning Electron Microscope. The photoluminescence property was studied under blue excitation. The XRD pattern of prepared phosphor well matches with ICDD (International center for diffraction data) file. Surface morphology of prepared phosphors was found to be in submicron range. Photoluminescence emission spectra of Eu~(2+) doped CaS and SrS exhibits broad emissions centered at 630 and 602 nm respectively corresponding to ~4F_6 ~5D_1 → ~4F_7 transition. It was also observed that the samples showed an emission that persisted for a few seconds after the excitation beam is turned off. CIE coordinates are (0.6263, 0.3328) and (0.5772, 0.4166) respectively under the excitation at 469 nm. The prominent excitation peaks located at 469 nm (blue light i.e. 440-480 nm), which indicates that the phosphors are promising material for a color converter using blue LED as the primary light (pumping) source in phosphor converted white LED (pc wLED) for solid state lighting.