Tunable luminescence properties of the novel Tm³⁺- and Dy³⁺-codoped LiLa(MoO₄)_x(WO₄)_2−x phosphors for white light-emitting diodes

Abstract

A series of Tm 3+ -and Dy 3+ -codoped LiLa(MoO 4 ) X (WO 4 ) 2-X phosphors were prepared via the conventional solid-state reaction method. It was discovered that both the optimum single doped concentration of Tm 3+ and Dy 3+ are 0.04 for LiLa(WO 4 ) 2 host, LiLa(WO 4 ) 2 :0.04Tm 3+ and LiLa(WO 4 ) 2 :0.04Dy 3+ will emit blue and yellow light, respectively. On the other hand, the emission colors of Tm 3+ -and Dy 3+ -codoped LiLa(WO 4 ) 2 could be tuned from blue to white through tuning the 10 energy transfer. With increasing the Dy 3+ doped concentration, the energy transfer efficiency of LiLa(WO 4 ) 2 :0.005Tm 3+ ,yDy 3+ increased gradually and reached as high as 88% when the concentration of Dy 3+ is 0.05. The energy transfer from Tm 3+ to Dy 3+ was revealed to be resonant type via the quadrupolequadrupole mechanism. As for the LiLa(MoO 4 ) X (WO 4 ) 2-X :0.005Tm 3+ ,0.03Dy 3+ phosphors, both the emission intensity of Tm 3+ and Dy 3+ were found to reach a maximum when the molar ratio of Mo/W is 15 0:2. In addition, with increasing the proportion of MoO 4 2-, the location of the chromaticity coordinates changed from the edge to the center of the white area. The chromaticity coordinate when the relative ratio of Mo/W is 2:0 was much closer to the standard chromaticity coordinate for white. The results indicate that these phosphors may have potential applications in the fields of UV-excited white light-emitting diodes.

Tunable white-light emission via energy transfer in single-phase LiGd(WO4)2:Re3+ (Re = Tm, Tb, Dy, Eu) phosphors for UV-excited WLEDs

“…can be seen that the central W 6+ is coordinated by four oxygen atoms at a tetrahedral site and the Li + and Gd 3+ cations are randomly distributed over the same site positions and are coordinated by eight oxygen atoms to form a distorted polyhedron with symmetry S 4 (without an inversion center). [29][30][31] Based on the similar effective ionic radii and charge balance, the Tm 3+ , Tb 3+ , Dy 3+ and Eu 3+ ions are expected to occupy Gd 3+ sites in LiGd(WO 4 ) 2 .…”

Crystal structure, tunable luminescence and energy transfer properties of Na3La(PO4)2:Tb3+,Eu3+phosphors

“…The multicolor tuning of phosphors has been achieved by co-doping RE 3+ ion into suitable host lattice, such as Eu 3+ -Bi 3+ , 20 Tm 3+ -Dy 3+ (ref. 21) and Tb 3+ -Eu 3+ . [22][23][24] It has been reported that Na 3 La(PO 4 ) 2 crystallizes in the orthorhombic structure.…”

A new single-phase white-light-emitting CaWO4:Dy3+ phosphor: synthesis, luminescence and energy transfer

“…As a result, numerous efforts have recently been made to develop the single-phase white-light-emitting phosphors based on the mechanism of energy transfer from sensitizer to activator, such as Ce 3+ /Mn 2+ , Eu 2+ /Mn 2+ , Ce 3+ /Eu 2+ , Tm 3+ /Dy 3+ etc. [11][12][13][14][15][16] Note that the above examples based on energy transfer to obtain white light are realized by co-doping various luminescent ions into one host. However, some hosts, such as niobate, vanadate and tungstate, themselves contain luminescent centers that can generate broad ultraviolet-visible emissions and effectively transfer their energy to an activator ion.…”