Luminescent properties of phosphor converted LED using an orange-emitting Rb_2CaP_2O_7:Eu~(2+) phosphor

摘要

A series of orange-emitting Rb_2CaP_2O_7:Eu~(2+) phosphors were synthesized by a conventional solid-state reaction method. The as-prepared phosphors were characterized by X-ray powder diffraction (XRD), fluorescence spectroscopy, and spectroradiometry. XRD showed that all prepared samples exhibited a monoclinic Rb_2CaP_2O_7 phase. Fluorescence spectroscopy showed that the photoluminescence efficiency of Rb_2Ca_(1-x)P_2O_7:Eu_x~(2+) phosphors increased with increasing Eu~(2+) concentration until x = 0.006, then decreased at higher concentrations, due to a concentration quenching effect. The thermal activation energy was also measured to be 0.40 eV. Furthermore, a phosphor-converted LED (pc-LED) coated with Rb_2Ca_(0.994)P_2O_7:Eu_(0.006)~(2+) was fabricated, which exhibited bright orange emission under a forward bias, from 200 to 300 mA. The color rendering index (CRI) of pc-LED coated with Rb_2Ca_(0.994)P_2O_7:Eu_(0.006)~(2+) was higher than the CRI of pc-LED coated with commercial red phosphor, due to the broad emission band of Rb_2CaP_2O_7:Eu~(2+) phosphor. In applying with three-band pc-LEDs, moreover, white pc-LED using Rb_2CaP_2O_7:Eu~(2+) phosphor had a higher CRI, than using commercial phosphor. These results indicated that Rb_2CaP_2O_7:Eu~(2+) phosphor could be a good candidate for a near-UV based w-LED.