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Dyes embedded YAG:Ce3+@SiO2 composite phosphors toward warm wLEDs through radiative energy transfer: Preparation, characterization and luminescence properties

Abstract

As the prevailing yellow phosphors for wLEDs, Y3Al5O12:Ce3+ (YAG:Ce3+) suffers from the deficiency of red in the spectral content of light. In this paper, a new strategy was provided to tailor the Ce3+ spectral profile through surface-located dye molecules of ATTO-Rho101, which features intense and broad absorption in the green-yellow spectral region of Ce3+ emissions as well as bright red emissions. Sphere-shaped and highly dispersed micrometer and nanometer-sized YAG:Ce3+ (micro/nano-YAG:Ce3+) were synthesized through a modified solvothermal method. Surface SiO2 coating and simultaneous dye embedding were performed on solvothermally derived YAG:Ce3+, heat-treated micro-YAG:Ce3+ and commercial phosphors. An efficient radiative transfer/ reabsorption from Ce3+ in YAG inner core to dye molecules in SiO2 outer shell, irrespective of the size of phosphors, was demonstrated in the accumulated powders of YAG:Ce3+@SiO2+dye upon blue light excitation, and then enhanced the red emissions. Fluorescence microscope was demonstrated to be a powerful tool to identify the reabsorption phenomenon of powdered materials. Packaging the heat-treated micro-YAG:Ce3+@SiO2+dye phosphors on the blue LED chips yielded a warm wLED (Ra~93), but an only Ra~79 of wLED was obtained with commercial YAG:Ce3+@(SiO2+dye)5 due to the low concentration of phosphors dispersions in epoxy resin and then the reduced reabsorption by dye molecules. Surface-protonated amine species were found to induce Ce3+→Ce4+ oxidation upon activation by heating or photoirradiation, and then quench the photoluminescence (PL) of micro-YAG:Ce3+ even after surface modification by SiO2, YAG or being embedded in epoxy resin matrix. High temperature of calcinations greatly improved the PL stability of micro-YAG:Ce3+ through the removal of surface-capped species. The dye in the silica matrix showed high stability against heating and irradiating due to the so-called “caging effects”, but a reduced photo-stability was found in commercial YAG:Ce3+@(SiO2+dye)5 due to the incomplete and/or loose SiO2 layer grown during multiple surface modifications.

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Publication details

The article was received on 10 Sep 2018, accepted on 07 Nov 2018 and first published on 08 Nov 2018


Article type: Paper
DOI: 10.1039/C8NR07360K
Citation: Nanoscale, 2018, Accepted Manuscript
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    Dyes embedded YAG:Ce3+@SiO2 composite phosphors toward warm wLEDs through radiative energy transfer: Preparation, characterization and luminescence properties

    G. Pan, H. Wu, S. He, L. Zhang, Z. Hao, X. Zhang and J. Zhang, Nanoscale, 2018, Accepted Manuscript , DOI: 10.1039/C8NR07360K

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