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 Tb3+ 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.
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+.
To convert ultraviolet(UV) light into near-infrared(NIR) light in phosphors is demanded for the development of solar cells.A series of NaYF_4:Nd^(3+),Yb^(3+) white powder samples were prepared via the hydrothermal method.The crystal structure and photoluminescence properties of the samples were carefully studied using X-ray diffractometry(XRD) and photoluminescence spectra.The excitation and emission spectra of NaYF_4:Nd^(3+),Yb^(3+) samples and the luminescence decay curves of Nd^(3+) and Yb^(3+) revealed an efficient energy transfer process from Nd^(3+) to Yb^(3+).This process resulted in the Yb^(3+) NIR fluorescent emission at 980 nm.Moreover,the lifetime of the Nd^(3+4)F_(3/2) level decreased with the increase of Yb^(3+) doping concentration.The build-up time of the decay curves of the Yb^(3+2)F_(5/2) level further verified the energy transfer process.Meanwhile,energy transfer efficiency based on different Yb^(3+) doping concentrations was achieved.
