Luminescent properties of phosphor converted LED using an orange-emitting Rb2CaP2O7:Eu2+ phosphor

A series of orange-emitting Rb2CaP2O7:Eu2+ 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 Rb2CaP2O7 phase. Fluorescence spectroscopy showed that the photoluminescence efficiency of Rb2Ca1−xP2O7:Eux2+ phosphors increased with increasing Eu2+ 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 Rb2Ca0.994P2O7:Eu0.0062+ 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 Rb2Ca0.994P2O7:Eu0.0062+ was higher than the CRI of pc-LED coated with commercial red phosphor, due to the broad emission band of Rb2CaP2O7:Eu2+ phosphor. In applying with three-band pc-LEDs, moreover, white pc-LED using Rb2CaP2O7:Eu2+ phosphor had a higher CRI, than using commercial phosphor. These results indicated that Rb2CaP2O7:Eu2+ phosphor could be a good candidate for a near-UV based w-LED.