Spectral investigation of R, Ce:YAG (R: Pr³⁺, Eu³⁺, Gd³⁺) single crystals and their applications in white LEDs

Eu³⁺, Pr³⁺, or Gd³⁺ codoped Ce:YAG single crystals were grown by using the Czochralski method. The photoluminescence (PL) emission and excitation spectra and transmittance were measured and investigated. The additional red-emitting bands were observed in the PL emission spectra of Eu,Ce:YAG and Pr,Ce:YAG single crystals and the formation of noticeable peaks was studied with reference to the schematic energy level diagrams. A red-shifted phenomenon was observed in the PL emission spectrum of Gd,Ce:YAG. With codoped Eu³⁺, Pr³⁺, or Gd³⁺ ions, warmer white light was achieved for the white light emitting diodes and the color rendering index became higher.