Solvothermally grown Ce~(3+)-doped Y_3Al _5O_(12) colloidal nanocrystals: Spectral variations and white LED characteristics

摘要

Alcoholic media dispersible YAG: Ce colloidal nanocrystals were prepared by a solvothermal route. To obtain highly efficient nanocrystals, the Ce concentration and the reaction time were optimized. The surface of the nanocrystals was further modified with oleylamine to make them dispersible in a non-polar solvent. The luminescent characteristics such as luminescent efficiency, band width and peak wavelength of Ce~(3+) d → f transition of the YAG: Ce nanocrystals were compared with those of a micrometre-sized phosphor. The host of nanocrystals was compositionally modified by partially or completely substituting Y~(3+) with Tb~(3+) or Gd~(3+) ions, through which the Ce~(3+) emission peaks were red-shifted due to an increased crystal field strength around Ce~(3+) luminescent centres. White light-emitting diodes (LEDs) were fabricated by coating these YAG: Ce nanocrystals on blue LED chips and their electroluminescent properties were compared with those of a bulk YAG: Ce-based white LED.