A cyan-emitting phosphor Ca3SiO4(Cl,Br)2:Eu2+ with high efficiency and good thermal stability for full-visible-spectrum LED lighting

Abstract

In this study, Ca2.98SiO4Cl2-yBry:0.02Eu2+ cyan-green phosphors with high efficiency and good thermal stability were prepared by a low temperature synthesis. The crystal structure, luminescence properties and thermal stability of as-prepared phosphors were systematically investigated by means of X-ray diffraction (XRD), photoluminescence excitation spectra (PLE), photoluminescence spectra (PL), CIE coordinates and variable temperature spectra. Simply increasing Br− in Ca2.98SiO4Cl2-yBry:0.02Eu2+, the emission peak can be shifted from 502 nm to 491 nm under near-UV (n-UV) excitation, which can make amends for the cyan gap (480–520 nm) and realize high color rendering. The remarkable blue shift of the emission band can be ascribed to the small crystal field splitting and Stokes shift. The external quantum efficiency of Ca3SiO4ClBr:Eu2+ moves up to 55.58% and exhibits an impressively absorption efficiency. Furthermore, a white LED device was fabricated via blue-emitting Sr5(PO4)3Cl:Eu2+, green-emitting YAGG:Ce3+, red-emitting (Ca,Sr)AlSiN3:Eu2+, and the cyan phosphor Ca3SiO4(Cl,Br)2:Eu2+ with 410 nm-chip. The WLED exhibits a warm and bright white light with low correlated CCT (3969 K), high Ra (96.9), and CIE color coordinates of (0.3828,0.3810). The results indicate that Ca2.98SiO4Cl2-yBry:0.02Eu2+ can be used as a potential cyan phosphor for full-spectrum warm white LED.