The determining factor of the luminescence energies of vanadate phosphors

Abstract

The molecular orbital calculations based on the DV-X¡ method were carried out for several vanadate phosphors of Sr 2 VO 4 Cl, Ca 2 VO 4 Cl, Ba 2 V 2 O 7 , Mg 3 (VO 4) 2 , and Zn 3 (VO 4) 2 , of which the luminescent colors range from deepblue to yellow through green. The structural refinement with the X-ray diffraction technique preceded the DV-X¡ calculations to provide a theoretical interpretation on the relationship between the crystal structures and the luminescent colors (luminescence energies) of the vanadate phosphors. The partial density of states obtained in the DV-X¡ calculations reasonably explained the lowest excitation energies of the vanadate phosphors. The calculations also exhibited the difference in the bonding characters among the ligand oxygens in a VO 4 tetrahedron due to the structural distortion. The relatively large contributions of the ionically coordinated oxygens were proposed on determining the luminescence energies. A linear correlation was deduced between the luminescence energies and the averaged VO distances with the selected oxygens ionically coordinated to V.

Highly Efficient Cyan-Green Emission in Self-Activated Rb3RV2O8 (R = Y, Lu) Vanadate Phosphors for Full-Spectrum White Light-Emitting Diodes (LEDs)

“…There are also slight red shifts in the position of the Em 1 (548.67 → 551.11 nm) and Em 2 (486.27 nm → 488.19 nm) bands of Rb 3 LuV 2 O 8 , compared with Rb 3 YV 2 O 8 . The red shift of all the bands may be due to the change in strength of the Stokes shift (Δ S ) caused by the increase of V–O bond length of Rb 3 LuV 2 O 8 . The evaluated Δ S of Rb 3 LuV 2 O 8 phosphor is 6935 cm –1 , which is slightly higher, compared to 6144 cm –1 of Rb 3 YV 2 O 8 .…”

New Structural Design Strategy: Optical Center VO4-Activated Broadband Yellow Phosphate Phosphors for High-Color-Rendering WLEDs

“…These broad excitation bands are attributable to the CT absorption from the ground state 1 A 1 to the excited states 1 T 2 and 1 T 1 of VO 4 groups. 63,64 As the number of VO 4 centers increases, we observe that the excitation intensity of KBCP 2−x V x phosphors gradually increases, along with a spectral red shift from 341 to 356 nm. The red shift of the excitation spectra is attributable to the transition probability of 1 A 1 − 1 T 1 gradually increasing with increasing V 5+ content (Figure S2).…”

Structures, photoluminescence, and principles of self-activated phosphors

“…Its PL emission spectrum depicted a broadband emission ranging from 400 nm to 650 nm, which was due to the charge transfer in the [VO 4 ] 3− group. Matsushima 67 researched the factors determining the luminescence energies of vanadate phosphors. The partial density of states obtained in the DV-Xα calculations reasonably explained the lowest excitation energies and exhibited the difference in the bonding characters among the ligand oxygens in the VO 4 tetrahedron due to the structural distortion.…”