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

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 Ba_8.4Eu_0.6Lu₂Si₆O₂₄ 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⁺.