Crystal-Site Engineering of Novel Na 3 KMg 7 (PO 4 ) 6- x (BO 3 ) x :Eu 2+ 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 Na 3 KMg 7 (PO 4 ) 6- x (BO 3 ) x :Eu 2+ (NKMPB:Eu 2+ ) phosphor via crystal-site engineering. This phosphor is derived from the Na 3 KMg 7 (PO 4 ) 6 :Eu 2+ 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 (BO 3 ) 3- units can manipulate the site-selective occupation of Eu 2+ activators, asymmetrically broadening the emission spectrum in NKMPB:Eu 2+ . Considering detailed luminescence performance analysis and the density functional theory calculations, a new substitution pathway of Eu 2+ is created by substituting (PO 4 ) 3- with (BO 3 ) 3- units, making partial Eu 2+ ions enter the Mg 2+ (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:Eu 2+ , the constructed NKMPB:Eu 2+ -based wLEDs show better color rendering ability (∼90.9) than that of Na 3 KMg 7 (PO 4 ) 6 :Eu 2+ -based wLEDs (∼86.3), and also demonstrate its great potential in full-spectrum healthy lighting.