Li⁺ Ion Induced Full Visible Emission in Single Eu²⁺‐Doped White Emitting Phosphor: Eu²⁺ Site Preference Analysis, Luminescence Properties, and WLED Applications

Abstract A series of Eu²⁺ single doped Ca₉Na_1–xLi_xSc_0.667(PO₄)₇ phosphors with full‐spectrum emission have been synthesized. Under the 385 nm excitation, the Eu²⁺ single doped Ca₉NaSc_0.667(PO₄)₇ without Li⁺ doping displays a broad cold white light emission with the peaks at about 480 and 610 nm. With the introduction of Li⁺ ions, the Eu²⁺ ions selectively occupy the Ca1, Ca2/Ca3, and Na sites. The variation of local environment of Eu²⁺ ions caused by Li⁺ ions enhances the luminous intensity, solves the problem of the lack of a red light component, and realizes the emission color tuning from cold white via warm white to orange. A special charge compensation method caused by Li⁺ migration avoids the generation of defects and is beneficial to the improvement of luminescence properties. Eventually, a warm white light‐emitting diode device is prepared by combining the white emitting Ca₉Na_0.8Li_0.2Sc_0.667(PO₄)₇:2%Eu²⁺ phosphors with 385 nm LED chip, which exhibits a high color‐rendering of 92.9, low correlated color temperatures of 4529 K, and excellent color stability under working temperature. The as‐reported warm white emitting Eu²⁺‐doped phosphors have potential applications in full‐spectrum solid‐state lighting. The site engineering strategy provides an extensive guide for optimizing and designing novel single‐composition white‐emitting phosphor materials.