Crystal-site engineering for developing tunable green light emitting Ba9Lu2Si6O24:Eu2+ phosphors for efficient white LEDs

Abstract

Phosphors with tuning capabilities in their excitation and emission spectra are in high demand in the field of advanced optical technology. In this article, Eu2+ doped Ba9Lu2Si6O24 (BLSO: Eu2+) phosphors, which emit an intense light hat can be tuned from dark blue (463 nm) to efficient green (514 nm), were produced, simply by increasing the Eu2+ concentration in the BLSO host lattice. This tuning capability suggests that there are multiple and distinguishable crystallographic sites in the host lattice of the BLSO phosphors. The Eu2+ activators exhibit preferable site distributions in the BLSO host lattice, depending on the Eu2+ concentration. This offers the possibility for engineering the appropriate site surroundings, available for the Eu2+ activators. The Ba8.4Eu0.6Lu2Si6O24 phosphor displays a prominent yellowish-green emission under blue light (440 nm) excitation, compared to the dark blue emission of BLSO: 0.1Eu2+ phosphors. The green emission from the BLSO: xEu2+ phosphor is closely associated with the specific coordinating environment of the Eu2+ activator in various crystallographic Ba sites. However, concentration quenching phenomena results in intensity decrease, a problem which is then solved by introducing Sr2+.