Broad near-ultraviolet and blue excitation band induced dazzling red emissions in Eu³⁺-activated Gd₂MoO₆ phosphors for white light-emitting diodes

Abstract

A series of Eu3+-activated Gd2MoO6 phosphors were synthesized via a citric acid-assisted sol–gel route.

Eu3+-activated La2MoO6-La2WO6 red-emitting phosphors with ultrabroad excitation band for white light-emitting diodes

“…The first broad band, which is marked as CT(I), ranging from 220 to 320 nm centered at around 283 nm is assigned to the charger transfer from the oxygen ligands to tungsten ions 12,46 . Moreover, the second broad band, named as CT(II), with a central wavelength of 379 nm, which matches well with the commercial NUV LED chip, is related to the overlapped transitions of O 2−  → Mo 6+ and O 2−  → Eu 3+   28,32 . The sharp absorption band at 462 nm is ascribed to the 7 F 0  →  5 D 2 transition of Eu 3+ ions 33 .…”

“…1(a)), it is evident that all the samples exhibit similar diffraction patterns. According to previous literatures 28,39,40 , one knows that the resultant compounds consist of the mixed phases of La 2 MoO 6 (ICSD#25611) and β -La 2 WO 6 (ICSD#246256), revealing that the Eu 3+ ions are incorporated into the host lattices and Eu 3+ -activated La 2 MoO 6 -La 2 WO 6 red-emitting phosphors are successfully prepared. Moreover, with the increase of Eu 3+ ion concentration, the diffraction peaks shift to larger angle which is attributed to inconsistent ionic radii between the Eu 3+ and La 3+ ions, as displayed in Fig.…”

“…In particular, the 5 D 0  →  7 F 1 transition is regarded as the magnetic dipole transition (∆ J  = 0, ±1) which is insensitive to the crystal environment surrounding the Eu 3+ ions, whereas the red emission corresponding to the 5 D 0  →  7 F 2 transition pertains to the hypersensitive electric dipole transition (∆ J  ≤ 6, when J or J ′ = 0, ∆ J  = 2, 4, 6) and its intensity is largely dependent on the crystal field around the Eu 3+ ions. In general, the 5 D 0  →  7 F 2 transition prevails in the luminescent spectrum when the Eu 3+ ions occupy the sites with non-inversion symmetry, while the yellow emission ( 5 D 0  →  7 F 2 ) becomes the strongest one when the Eu 3+ ions are located at symmetric cation circumstance 28,47 . As described in Fig.…”

“…To solve this problem, an appropriate luminescent host material should be selected. According to previous literatures, one obtains that the tungstates and molybdates are promising candidates for luminescent host materials because of their outstanding metrics of high stability, low phonon energy, relatively low synthetic temperature and admirable intrinsic luminescent performance 28–30 . Meanwhile, both the tungstates and molybdates exhibit a broad absorption band in the UV region arising from the charge transfer (CT) transitions of O 2−  → W 6+ and O 2−  → Mo 6+ , respectively 31,32 .…”

Dual-Mode Manipulating Multicenter Photoluminescence in a Single-Phased Ba9Lu2Si6O24:Bi3+, Eu3+ Phosphor to Realize White Light/Tunable Emissions

“…As next-generation lighting devices, phosphor-converted white light-emitting diodes (w-LEDs) have received much more attention since w-LEDs provide extraordinary superiorities, such as low electric consumption, high electro-optical conversion efficiency, high brightness, good stability, fast response, and environmental friendliness 7–10 . Until now, combining blue-emitting InGaN-based LED chips and yellow-emitting Y 3 Al 5 O 12 :Ce 3+ phosphors to make white light emission is one of the simplest and most efficient ways for commercial application 11,12 .…”