In this study, the optical properties of nanocrystalline europium doped yttria, Y2O3:Eu3+ were investigated in dependence on different caging hosts such as porous MCM-41, porous silica, and porous alumina with pore sizes ranging between 2.7 to 80 nm. These results were compared to nanopowders measured in air and aqueous solution whose particle sizes were 5 nm and 8 nm, respectively. All these results were compared to a commercial lamp phosphor powder with a grain size of about 5 μm. The structural properties of the samples were determined by x-ray diffraction and transmission electron microscopy. Investigated optical properties are the photoluminescence emission spectra, the excitation spectra, the lifetimes, and the quantum efficiencies. A heavy dependence of the charge transfer process on the surrounding will be reported and discussed.
White phosphor converted LEDs have become an important technology for innovative lighting applications. This paper compares white LEDs that were built by using only one phosphor (dichromatic concept) with LEDs employing mixtures of two phosphors (trichromatic LEDs), a green and a red luminescent material, and discusses the impact of these concepts on the quality of light, in particular the differences in color rendition.
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