F. Xiao

A red-emitting Ca8MgLa(PO4)7:Ce3+,Mn2+ phosphor for UV-based white LEDs application

Ca(8)MgLa(PO(4))(7):Ce(3+),Mn(2+) phosphors have been prepared by a conventional solid state reaction under a weak reductive atmosphere. The crystal structure and photoluminescent properties were investigated. It was found that the red emission at 640nm originated from the (4)T(1)((4)G)→(6)A(1)((6)S) transition of Mn(2+) increases dramatically by a factor of 6.4 with the optimum Ce(3+) co-doping. The energy transfer from Ce(3+) to Mn(2+) was proposed to be resonance-type via an electric dipole-dipole mechanism and the energy transfer efficiency was also calculated by the relative emission intensity. With the broadband ultraviolet (UV) absorption of Ce(3+) and the suitable color coordinates, Ca(8)MgLa(PO(4))(7):Ce(3+),Mn(2+) phosphors might be a promising candidate as red phosphors in the field of UV-based white light-emitting diodes.

Enhanced red light emission from LaBSiO5:Eu3+,R3+ (R=Bi or Sm) phosphors.

Polycrystalline LaBSiO5:Eu3+,R3+ (R=Bi or Sm) phosphors have been synthesized by a facile sol-gel method. The phosphors have been characterized by thermogravimetric analysis/different scanning calorimeter, scanning electron microscopy, X-ray diffractometer and fluorescence measurements. It was found that the emission intensity of LaBSiO5:Eu phosphors increases clearly and reaches a maximum at 30 mol% with increasing of Eu3+ concentration. The incorporation of Bi3+ ions and/or Sm3+ ions have greatly enhanced the emission intensity of Eu3+ upon excitation with 391 nm light. The possible sensitization mechanisms of Sm3+ and/or Bi3+ on Eu3+ emission intensity have been investigated and discussed. The high brightness and short luminescence decay times make it promising red-emitting candidates for white light-emitting diodes.

Bi3+ sensitized Y2WO6:Ln3+ (Ln=Dy, Eu, and Sm) phosphors for solar spectral conversion.

The phosphors of Y2WO6:Bi3+, Ln3+ (Ln=Dy, Eu and Sm) were synthesized by solid-state reaction in this study. The crystal structure, photoluminescence properties and energy transfer mechanism were investigated. By introducing Bi3+ ions, the excitation band of the phosphors was broadened to be 250-380 nm, which could be absorbed by the dye-sensitized solar cells (DSSCs). The overlap between excitation of W-O groups/Bi3+ and the emission of Ln3+ (Dy, Eu, and Sm) indicated that the probability of energy transfer from W-O groups and Bi3+ to Ln3+. The energy transfer efficiency from Bi3+ to Ln3+ (Ln=Dy, Eu and Sm) are calculated to be 16%, 20% and 58%. This work suggested that Y2WO6:Bi3+, Ln3+ (Ln=Dy, Eu and Sm) might be a promising ultraviolet-absorbing luminescent converter to enhance the photoelectrical conversion efficiency of dye-sensitized solar cells (DSSCs).

A yellow-emitting phosphor of Mn2+-doped Na2CaP2O7

A yellow-emitting Na2CaP2O7:Mn(2+)phosphors have been synthesized by solid state reaction. The crystal structure, photoluminescence properties as well as concentration quenching mechanism have been investigated. The (4)T1-(6)A1 emission of Mn(2+)in Na2CaP2O7 phosphor ranges from 500 to 650 nm and exhibits a red shift while increasing the Mn(2+)concentration. The crystal field strength is calculated based on the combination of excitation spectrum and Tanabe-Sugano diagram. The chromaticity coordinates of Na2CaP2O7:Eu(2+), Mn(2+)phosphors were discussed in order to develop the potential application in white light-emitting diodes (LEDs).

Luminescence properties of cerium doped silicon nitride with MgO additive

This work focuses on the luminescent materials Si3N4:Ce3+ with magnesium oxide additive prepared by the solid-state reaction method. The detailed phase formation was investigated based on X-ray diffraction profiles. The photoluminescence (PL) and photoluminescence excitation (PLE) spectra, the decay lifetime depend on the concentration of doped-Ce3+ ion and MgO additive were investigated. The emission intensity was effectively enhanced approximately 18.7 times ascribing to MgO additive. Si3N4:Ce3+ phosphor shows good absorption in ultraviolet (UV) region and emits broad blue emission, which can be used as a potential candidate for application in phosphor-converted light emitting diodes (LEDs).

Selective enhancement of red upconvesion luminescence of Er 3+ by doping with Mn 2+ ions

Well-defined KZnF₃:Yb³⁺, Er³⁺, Mn²⁺ nanocubes were successfully prepared by a facile solvothermal method. The XRD and SEM measurements results show that the cubes have good crystallinity and the average cubic size is about 40 nm The incorporation of Mn²⁺ ions into KZnF₃:Yb³⁺, Er³⁺ leads to the great increase in the red to green luminescence intensity ratios from 10:1 to 214:1 and the red emission was enhanced about 20 times. The selective enhancement of red upconversion luminescence of Er³⁺ can be ascribed to the exchange energy transfer interactions between Er³⁺ ions and Yb³⁺-Mn²⁺ dimers. The case of KZnF₃:Yb³⁺, Er³⁺, Mn²⁺ provides a new strategy to get the pure red upconversion luminescence, which show potential applications in the fields of lighting, displays and biological nano labels.