Compositional tuning and site engineering of Sr-alloyed Ca3(PO4)2:Mn2+, Eu2+ towards multicenter-activated single-component white light emitter

Abstract

As a promising alternative to traditional light sources, the phosphor-converted white light-emitting diodes (WLEDs) have rapidly emerged in the fields of lightings and displays. In our work, a novel single-component warm white phosphor Ca2Sr(PO4)2:Mn2+, Eu2+ was successfully designed and synthesized based on multicenter emission and crystal site engineering. The phosphors were confirmed to have a high phase purity according to X-ray diffraction (XRD) analysis and the scanning electron microscope (SEM). Further XRD Rietveld refinements unraveled the preferential site occupations of both alloying element (Sr) and dopants (Mn and Eu). The feasible site engineering can confine the Mn and Eu dopants in different Ca sites, resulting in regulated optical behaviors. Density functional theory (DFT) calculations were also employed to shed light on the site engineering from the theoretical aspects, which suggest an enlarged formation energy gap for different site occupations after Sr alloying. Finally, a single-component WLED based on a near-ultraviolet (n-UV) chip was successfully fabricated with high color rendering index (Ra = 91.2) and luminous efficacy (65.2 lm/W). The device has also proved its excellent stability via a series of tests, showing the great potential of Ca2Sr(PO4)2:Mn2+, Eu2+ as phosphors in lighting applications.