Crystal-Site Engineering of Novel Na3KMg7(PO4)6–x(BO3)x:Eu2+Phosphors for Full-Spectrum Lighting

The “cyan gap” is the bottleneck problem in violet-driven full-spectrum white-light-emitting diodes (wLEDs) in healthy lighting. Accordingly, we develop a novel broadband-blue-cyan emission Na3KMg7(PO4)6–x(BO3)x:Eu2+(NKMPB:Eu2+) phosphor via crystal-site engineering. This phosphor is derived from the Na3KMg7(PO4)6:Eu2+phosphor, which shows desired abundant cyan emissive components. A comparative study is conducted to reveal the microstructure–property relationship and the key influential factors to its spectrum distribution. It can be found that the introduced (BO3)3–units can manipulate the site-selective occupation of Eu2+activators, asymmetrically broadening the emission spectrum in NKMPB:Eu2+. Considering detailed luminescence performance analysis and the density functional theory calculations, a new substitution pathway of Eu2+is created by substituting (PO4)3–with (BO3)3–units, making partial Eu2+ions enter the Mg2+(CN = 5, CN = 6) crystallographic sites, and yielding an extra emission band at 600 nm (16667 cm–1) and especially 501 nm (19960 cm–1). Meanwhile, a high-color-quality full-spectrum-emitting wLEDs was fabricated, upon 100 mA forward-bias current driven. Due to the achieved extra cyan emissive components of NKMPB:Eu2+, the constructed NKMPB:Eu2+-based wLEDs show better color rendering ability (∼90.9) than that of Na3KMg7(PO4)6:Eu2+-based wLEDs (∼86.3), and also demonstrate its great potential in full-spectrum healthy lighting.