Li~+ Ion Induced Full Visible Emission in Single Eu~(2+)-Doped White Emitting Phosphor: Eu~(2+) Site Preference Analysis, Luminescence Properties, and WLED Applications

摘要

A series of Eu2+ single doped Ca9Na1-xLixSc0.667(PO4)(7) phosphors with full-spectrum emission have been synthesized. Under the 385 nm excitation, the Eu2+ single doped Ca9NaSc0.667(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 Ca9Na0.8Li0.2Sc0.667(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.