The phosphors that are able to convert vacuum ultraviolet(VUV) light into visible light are demanded for the development of novel displaying and lighting devices.NaYF4:Pr3+,Dy3+,NaGdF4:Pr3+,NaGdF4:Dy3+and NaGdF4:Pr3+,Dy3+were prepared by hydrothermal synthesis method and their luminescent properties in VUV-vis spectral region were investigated at room temperature.For NaYF4:Pr3+,Dy3+,no energy transfer process from Pr3+to Dy3+was observed.However,the introduction of Gd3+into the fluoride lattice led to intense Dy3+emissions upon Pr3+4f5d state excitation.Gd3+acted as an intermediate,resulting in efficient energy transfer from Pr3+to Dy3+in NaGdF4.Pr3+transferred most of its energy to Gd3+,and then the energy was transferred from Gd3+to Dy3+.So NaGdF4:Pr3+,Dy3+not only took full advantage of the intense Pr3+4f5d absorption,but converted the VUV excitation light into the near-white emission of Dy3+.
Energy transfer is a promising strategy to improve the visible light emitting efficiency of phosphors. A series of Ce3+, Tb3+, Dy3+ and/or EU3+ doped Na3Y(BO3)2 (NYB) were prepared by solid-state reaction and their photoluminescence properties were studied in detail. The excitation and emission spectra of NYB:Ce3+,Tb3+ and NYB:Ce3+,Dy3+ revealed that an efficient energy transfer process from Ce3+ to Zb3+ or Dy3+ occurred upon excitation Ce3+ into 5d level. The dependence of the decay times of Ce3+ 5d level on Tb3+ or Dy3+ concentration indicated that the energy transfer efficiency increased with increasing Tb3+ or Dy3+ content. So the UV excitation light could be converted into green or near-white emission. However, there was no obvious evidence of the existence of energy transfer from Ce3+ to Eu3+ in NYB.
To convert ultraviolet (UV) light into near-infrared (NIR) light in phosphors is demanded for the development of solar cells. A series of NaYF4:Nd3+,Yb3+ white powder samples were prepared via the hydrothermal method. The crystal structure and photolu-minescence properties of the samples were carefully studied using X-ray diffractometry (XRD) and photoluminescence spectra. The excitation and emission spectra of NaYF4:Nd3+,Yb3+ samples and the luminescence decay curves of Nd3+ and Yb3+ revealed an effi-cient energy transfer process from Nd3+ to Yb3+. This process resulted in the Yb3+ NIR fluorescent emission at 980 nm. Moreover, the lifetime of the Nd3+4F3/2 level decreased with the increase of Yb3+ doping concentration. The build-up time of the decay curves of the Yb3+2F5/2 level further verified the energy transfer process. Meanwhile, energy transfer efficiency based on different Yb3+ doping concentrations was achieved.