In this work, a method was developed to determine the concentration of Eu3+ and Tb3+\nions in a thin-film sample of SiO2, co-doped with ZnO-nanocrystals (ZnO-nc), to produce a sample of\nany desired colour in the International Commission on Illumination (CIE) colour space. Using this\nmethod, a white light emitting sample was fabricated. The thin-film sample combines red, green and\nblue emissions from the Eu3+ ions, Tb3+ ions and ZnO-nc, respectively, to create white light or light of\nany desired colour. The emissions at 614 nm and 545 nm from Eu3+ and Tb3+ ions, respectively, is due\nto the energy transfer from the excited ZnO-nc to the rare-earth (RE) ions. In this way, only a single\nexcitation wavelength is needed to excite the ZnO-nc, Eu3+ and Tb3+ ions in the sample to produce\nemission of a desired colour from the sample. We developed an empirical 4th-degree polynomial\nequation to determine the concentrations of Eu3+ and Tb3+ ions to produce light of any desired colour\nin the CIE colour space. Based on the above empirical equation, the concentration of Eu3+ and Tb3+\nions for a white light emitting sample was found to be 0.012 and 0.024 molar fractions, respectively.\nThe white light emission from the sample was confirmed by fabricating the sample using the low-cost\nsolâ??gel process. The stimulated emission spectra and the experimental emission spectra of the white\nlight sample fit very well. The results presented in this work are important to develop energy efficient\nsolid state lighting devices.
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