Multisite Cation Regulation of Broadband Cyan-Emitting (Ba_1-Sr)₉Lu₂Si₆O₂₄/Eu²⁺ Phosphors for Full-Spectrum wLEDs

Developing broadband cyan-emitting phosphors is an essential issue to achieve high-quality full-spectrum phosphor-converted white light-emitting diodes. Multisite cation regulation to modify the photoluminescence spectrum is a valid way to achieve broadband emission for phosphors. The Ba₉Lu₂Si₆O₂₄ lattice with various cation sites for activator ions is a preferred host for broadband emitting phosphors. The preferential crystallographic sites of Eu²⁺ in the Ba₉Lu₂Si₆O₂₄ lattice are identified based on the crystal field theory, crystal structure, and bond indices (such as NAC and SBOs) of the cations. Sr substitution in Ba₉Lu₂Si₆O₂₄/Eu²⁺ phosphor affects the location of Eu²⁺ activator ions, which is investigated via the first-principles density functional theory calculations, Rietveld refinement, and luminescence decay curves, and results in the modification of luminescence properties and thermal stability. The Sr-substituted (Ba_0.8Sr_0.2)₉Lu₂Si₆O₂₄/Eu²⁺ sample exhibits a broadband emission spectrum peaked at 471 and 518 nm with a large full width half maximum of 139 nm, covering blue-cyan-green regions, which can be an excellent candidate as broadband cyan-emitting phosphors for high-quality full-spectrum wLEDs.