Narrow-band red-emitting Li6Y1-x(BO3)3:xEu3+ phosphors with high R9 for WLEDs

Narrowband red-emitting phosphors excited by near-ultraviolet (near-UV) light can significantly improve the R 9 and are promising for white light-emitting diodes (WLEDs). In this work, Li 6 Y 1-x (BO 3 ) 3 :xEu 3+ is first reported as a novel narrowband red phosphor, which exhibits a high R 9 value (83.8) under near-UV chip excitation for fabricating WLEDs with high color rendering index (CRI). X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) confirmed that Eu 3+ successfully partially substituted Y 3+ in the Li 6 Y(BO 3 ) 3 lattice, and all samples maintained a monoclinic P 2 1 /c structure without impurity phases. Under 396 nm near-UV excitation, Li 6 Y 1-x (BO 3 ) 3 :xEu 3+ phosphors showed intense red emission at 616 nm (attributed to the Eu 3+ 5 D 0  →  7 F 2 transition) with a full width at half maximum (FWHM = 4.8 nm), and this narrowband feature directly contributes to the improved R 9 . The optimum Eu 3+ doping concentration was 0.07; at this concentration, the red-orange ratio (the intensity ratio of 5 D 0  →  7 F 2 to 5 D 0  →  7 F 1 transitions) reached a maximum value of 4.46, indicating Eu 3+ is in a low-symmetry crystal field with high red emission purity. The luminescent intensity at 423 K remained 68.9 % of that at room temperature, with an activation energy of 0.186 eV, demonstrating excellent high-temperature stability. When the optimal phosphor was mixed with commercial BaMgAl 10 O 17 :Eu 2+ blue and (Ba, Sr) 2 SiO 4 :Eu 2+ green phosphors and packaged on a 395–400 nm chip, the fabricated WLED exhibited a high CRI (R a  = 87) and a suitable correlated color temperature (CCT = 5753 K). The results demonstrate that Li 6 Y(BO 3 ) 3 :Eu 3+ is a very promising red phosphor candidate for high-CRI solid-state lighting