Browsing by Author "Chen, Shi-Fu"

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Optimization of the Single-Phased White Phosphor of Li2SrSiO4:Eu2+, Ce3+ for Light-Emitting Diodes by Using the Combinatorial Approach Assisted with the Taguchi Method
(2012-12-01)
Chen, Lei
;
Luo, Anqi
;
Zhang, Yao
;
Liu, Fayong
;
Jiang, Yang
The best performance of the phosphor Li2SrSiO4: Eu2+, Ce3+ in terms of luminescence efficiency (LE), color rendering index (CRI) and color temperature (Tc) for light-emitting diode application was optimized with combinatorial approach. The combinatorial libraries were synthesized with solution-based method and the scale-up samples were synthesized with conventional solid-reaction method. Crystal structure was investigated by using the X-ray diffraction spectrometer. The emission spectra of each sample in combinatorial libraries were measured in situ by using a fiber optic spectrometer. Fluorescence spectrometers were used to record excitation and emission spectra of bulk samples. White light generation was tuned up by tailoring Eu2+ and Ce3+ concentrations in the single-phased host of Li2SrSiO4 under near-ultraviolet excitation, but it exhibited low efficiency of luminescence and poor color rendering index. The effects of each level of the Eu2+ and Ce3+ concentrations on LE, CRI, and Tc were evaluated with the Taguchi method. The optimum levels of the interaction pairs between Eu2+ and Ce3+ concentration on LE, CRI, and Tc were [2,1] (0.006 M, 0.003 M), [1, 2] (0.003 M, 0.006 M), and [3, 1] (0.009 M, 0.00 3M), respectively. The thermal stability of luminescence, the external quantum efficiency (QE), luminance, chromaticity coordinates, correlated color temperature, color purity including the composition ratio of RGB in white light, and color rendering index of the white light emission of phosphor were evaluated comprehensively from a bulk sample.
The site-selective excitation and the dynamical electron-lattice interaction on the luminescence of YBO3: Sb3+
(2013-05-01)
Chen, Lei
;
Luo, An-Qi
;
Zhang, Yao
;
Chen, Xin-Hui
;
Liu, Hao
The phosphor of YBO3: Sb3+ was synthesized by solid state reaction. Its crystal structure was examined by using X-ray diffraction analysis. The morphology and particle size were characterized with a scanning electron microscopy. The properties of YBO3: Sb3+ luminescence was systematically studied by exciting borate host, the P-1(1) and P-3(1) levels of Sb3+ at the C-i and C-1 sites with 168, 203, 218, 252 and 262 nm, respectively, measured on the synchrotron radiation instruments. The different configurations of emission spectra excited with variant wavelengths show the character of wavelength-selective excitation, which was attributed to different occupations of the Sb3+ site in the YBO3 crystal lattice. Moreover, strong electron-lattice interaction (i.e., the Jahn-Teller effect) between Sb3+ and YBO3 host was discriminated by comparing low temperature and room temperature spectra. The site-selective luminescence was confirmed by YBO3 activated with multiple Sb3+ concentrations. The spectral assignment was verified with fluorescence lifetime achieved by using the Time-Correlated Single-Photon Counting method. (C) 2013 Elsevier Inc. All rights reserved.