Solvothermally grown Ce³⁺-doped Y₃Al₅O₁₂colloidal nanocrystals: spectral variations and white LED characteristics

Abstract

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 Ce3+ 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 Y3+ with Tb3+ or Gd3+ ions, through which the Ce3+ emission peaks were red-shifted due to an increased crystal field strength around Ce3+ 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.

Selecting Conversion Phosphors for White Light-Emitting Diodes

“…It has been suggested that the organic capping layer of YAG:Ce nanoparticles can be degraded by the light from a 450 nm pump LED [158].…”

“…On the other hand, the large surface-to-volume ratio in nanoparticles offers additional non-radiative decay paths, thus reducing the overall efficiency [159]. For YAG:Ce 3+ nanoparticles with a size of 7nm, the Ce 3+ emission is slightly blue-shifted compared to the bulk phosphor, while the emission intensity was halved [158]. It appears that much progress can still be made in the field of impurity-doped nanoparticles.…”

One-step synthesis of ZnO nanosheets: a blue-white fluorophore

“…These include ‘magic-sized’ CdSe [1] and a large variety of other materials in nano-particulate format, including CdSeS [2], Mn-doped ZnS [3], Mn-doped ZnSe [4], Ce 3+ -doped Y 3 Al 5 O 12 [5], doped YVO 4 :Ln 3+ , and silica-coated YVO 4 :Ln 3+ , where Ln 3+ = Eu 3+ , Dy 3+ , or Tm 3+ [6] mixtures of rare earth phosphors [7] and rare earth-doped GdF 3 [8]. In addition, another class of coating materials currently attracting attention is that of wide band-gap semiconductors such as Ga 2 O 3 [9], In 2 O 3 [10], and ZnO.…”

White Light Emission from NaCaPO4:Dy3+ Phosphor for Ultraviolet‐Based White Light‐Emitting Diodes

“…SSL in the form of light‐emitting diodes (LEDs) is budding as a highly competent field and is a subject of intense research. In this context, white light‐emitting diodes (w‐LEDs) are the promising new generation light source, which will be able to replace most gas‐discharge fluorescent lamps, due to their superior features in terms of reliability, long lifetime, excellent durability, low energy consumption, and environmental benefits 5–8 . Currently, several problems exist with commercial phosphor‐converted (pc) w‐LEDs composed of the blue emission from InGaN chips and the yellow emission from Ce 3+ ‐doped yttrium aluminum garnet (YAG:Ce 3+ ) phosphor 9–13 .…”