Materials Research Bulletin, Vol.47, No.12, 4522-4526, 2012
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:Eu-x(2+) 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: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 Rb2Ca0.994P2O7:Eu-0.006(2+) 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. (C) 2012 Elsevier Ltd. All rights reserved.