Enhanced fluorescence and heat dissipation of calcium titanate red phosphor based on silver coating
2015
Phosphor plays an important role in LEDs—the next generation of lighting source. However, many families of phosphor like titanate still face two severe problems: Low photoluminescence (PL) efficiency and poor thermal stability. Herein, the silver coating is applied to alleviate the above challenges. Ag nanoparticles with different morphology like disks or triangular plates are synthesised by a simple sol-reduction method, and then coated on the shape-regular CaTiO3:Eu (CTOE) phosphor. When the localized surface plasmon resonance (LSPR) extinction spectrum of Ag nanoparticles matches well with excitation or emission wavelength, the PL intensity of CTOE phosphor would be efficiently enhanced. There is an optimum point of LSPR coating amount due to the balance of LSPR-enhancement and scattering/reflection–reduction of Ag nanoparticles. The coating of Ag also leads to an improvement in heat dissipation of CTOE phosphors; meanwhile an overmuch of Ag would also reduce the luminous efficiency. Thus the most suitable coating amount based on the overall consideration successfully enables the enhancement of both PL intensity and heat dissipation, and the pc-LED lamp packaged with Ag coated CTOE phosphor also shows a higher efficiency and more stable working status than the uncoated ones.
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