Color-Tunable and Highly Luminous N^3–-Doped Ba_2–xCa_xSiO_4−δN_2/3δ:Eu²⁺ (0.0 ≤ x ≤ 1.0) Phosphors for White NUV-LED

Abstract

In the search for well-defined phosphor materials for white NUV-LEDs, the highly enhanced luminous efficacy by N(3-) doping as well as color tunability via Ca substitution has been successfully obtained in Ba2-xCaxSiO4-δN2/3δ:Eu(2+) (x = 0.0, 0.5, 0.8, 1.0) phosphors. With increasing Ca-substitution rate, the crystal structures of the phosphor materials are changed from the primitive orthorhombic structure to the hexagonal one, so that the CIE coordinates move from bluish-green (at Ca = 0.0), to blue (at Ca = 0.5), and finally to near white region (at Ca = 0.8 and 1.0) in these materials. In combination with the results from X-ray photoelectron spectroscopy (XPS) and infrared (IR) spectroscopy, the elemental distribution of the phosphor materials found from secondary-ion mass spectrometry (SIMS) directly indicates that the N(3-) ions are partially substituted for O(2-) ions into the crystal lattice of alkaline-earth orthosilicates and thus critically improves the color-tunable photoluminescence (PL) and electroluminescence (EL) efficiency of the phosphor materials for white NUV-LEDs. The newly found "the N(3-) doping and color-tunable effect" on large PL and EL enhancement may provide a platform in the discovery of new efficient phosphors for solid state lighting.

Highly Luminous Ba2SiO4−δN2/3δ:Eu2+ Phosphor for NUV-LEDs: Origin of PL-Enhancement by N3−-Substitution

“…The emission intensities at 150 • C greatly were decreased to about 40% of the initial one at ambient temperature, as previous research [44,45]. Kim et al reported that thermal stability of Ba 2−x Ca x SiO 4 :Eu 2+ (x = 0.5) phosphor were highly increased in comparison to that of Ba 2 SiO 4 :Eu 2+ phosphor [46]. Their results probably indicate that the thermal stability of phosphors is very closely related to the structural factor of the phosphors because Ba 2 SiO 4 :Eu 2+ phosphor with orthorhombic phase (space group = Pmcn) [11] was transformed into the hexagonal phase (space group = P3m1) [47] after partial Ca 2+ substitution for Ba 2+ .…”

New Insight for Luminescence Tuning Based on Interstitial sites Occupation of Eu2+ in Sr3Al2−xSixO5−xNxCl2 (x = 0–0.4)

“…Comparing with the cation substitution, nitridation of phosphors provides new inspiration to phosphors design . A well‐known fact is that the excellent thermal stability in some nitride phosphors comes from their high covalency and rigidity of structure .…”

Luminescence investigations of novel orange‐red fluorapatite KLaSr3(PO4)3F: Sm3+ phosphors with high thermal stability

“…However, the mixing of multi‐phosphors usually results in color imbalance and instability at higher temperatures, limiting their applications. To solve this problem, many efforts have been done to develop single‐phase emission‐tunable (by energy transfer) phosphors pumped with UV or n ‐UV chips . In addition, highly efficient phosphors can not only enhance the energy efficiencies but also present potential advantages in the CCT and CRI.…”

“…To solve this problem, many efforts have been done to develop singlephase emission-tunable (by energy transfer) phosphors pumped with UV or n-UV chips. [7][8][9] In addition, highly efficient phosphors can not only enhance the energy efficiencies but also present potential advantages in the CCT and CRI. Thus, novel efficient phosphors for improving the performances of solid-state lighting are interesting.…”