Photoluminescence and Ce3+→Tb3+→Eu3+ Energy Transfer Processes of the Ce3+/Tb3+/Eu3+-doped β-NaYF4 Phosphors with Broadened Excitation Spectrum

Ce3+/Tb3+ co-doped and Ce3+/Tb3+/Eu3+ tri-doped β-NaYF4 photoluminescent microcrystals using oleic acid as surfactant were synthesized using the solvothermal method. Their microstructural characteristics and photoluminescence properties were investigated in detail. They have the shape of hexagonal prism bipyramids with uniform particle size, which decreases with the concentrations of Tb3+ and Eu3+. The energy transfer processes of both the Ce3+→Tb3+ and the Ce3+→Tb3+→Eu3+ were systematically studied. Compared with Eu3+ or Tb3+ single-doped β-NaYF4 microcrystals, the sensitization by Ce3+ for the photoluminescence of Tb3+ and Eu3+ leads to a broad excitation spectral bandwidth in the ultraviolet (UV) range. Meanwhile, the corresponding optical absorption efficiency is greatly enhanced. High energy transfer efficiencies have been observed from Ce3+ to Tb3+ and from Tb3+ to Eu3+.