A promising single-phase, color-tunable phosphor (Ba0.9Sr0.1)9Lu2Si6O24: Eu2+, Mn2+ for near-ultraviolet white-light-emitting diodes

Abstract

A series of (Ba0.9Sr0.1)9Lu2Si6O24: Eu2+, Mn2+ phosphors have been synthesized by a solid-state reaction. The occupied position of rare earth ions can be successfully changed through Sr2+ ions replacing Ba2+ ions partly, therefore, the corresponding optical properties can be tuned. When Sr2+ ions replace Ba2+ ions by 10%, Eu2+ ions occupy not only alkaline earth 1(AE1) site to produce a blue emission bands centered at 460 nm but also AE2/AE3 site to generate a green emission bands centered at 520 nm, both of which are ascribed to the 4f65d1-4f7(8S7/2) transition of the Eu2+ ions. When co-doping Mn2+ ions, red broad emission centered at 595 nm originated from the 4T1(4G)-6A1(6S) transitions of Mn2+ ions can be added to the emission spectra of co-doped phosphors. There is energy transfer from Eu2+ to Mn2+ ions in the (Ba0.9Sr0.1)9Lu2Si6O24 host that have been confirmed to be a dipole-dipole interaction. The luminescent color from cool white to warm white even to orange-red can be adjusted by proper controlling the Mn2+ ions doping concentration. Furthermore, an excellent white LED device has been fabricated consisting of (Ba0.9Sr0.055)9Lu2Si6O24: 0.03Eu2+, 0.015Mn2+ phosphor and a 370 nm NUV-chip. This device presented an excellent correlated color temperature (CCT) of 4631 K and a high color-rendering index (CRI) of 83, indicating that the co-doped (Ba0.9Sr0.1)9Lu2Si6O24: Eu2+, Mn2+ phosphors will be a promising candidate as a single-phase, color-tunable phosphors for NUV-based white-light emitting diodes.