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.
