Effect of YAG:Ce Particle Size on Lighting Performance of High Color Temperature Multi-chip White LED (original) (raw)
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Transactions on Electrical and Electronic Materials, 2014
Most commercial white LED lamps use blue chip coated with yellow emitting phosphor. The use of blue excitable red and green phosphors is expected to improve the CRI. Several phosphors, such as SrGa 2 S 4 :Eu 2+ and (Sr,Ba)SiO 4 :Eu 2+ , have been suggested in the past as green components. However, there are issues of the sensitivity and stability of such phosphors. Here, we describe gallium substituted YAG:Ce 3+ phosphor, as a green emitter. YAG structures are already accepted by the industry, for their stability and efficiency. LEDs with improved CRI could be fabricated by choosing Y 3 Al 4 GaO 12 :Ce 3+ (green and yellow), and SrS:Eu 2+ (red) phosphors, along with blue chip. Also, the effect of a slight change in chip wavelength is studied, for two phosphor-coated w-LEDs. The reduction in particle size of the coated phosphors also gives improved w-LED characteristics.
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In this research paper, we introduced yellow-green MgCeAl11O19:Tb 3+ as a new phosphor ingredient to adapt to the quality requirements on the chromatic homogeneity and emitted luminous flux of modern multi-chip white LED lights (MCW-LEDs). The results from experiments and simulation show that employing MgCeAl11O19:Tb 3+ phosphor can lead to much better optical properties and therefore is a perfect supporting material to achieve the goals of the research. When the MgCeAl11O19:Tb 3+ phosphor is added into the phosphorus composite which already contains YAG: Ce 3+ particles, and the silicone glue, it affects the optical properties significantly. In other words, the concentration of this phosphor can determine the efficiency of lumen output and chromatic homogeneity of WLEDs. In specific, as the concentration of MgCeAl11O19:Tb 3+ go up, the luminous yield will increase accordingly, though there is an insignificant decrease in CQS. Moreover, if the MgCeAl11O19:Tb 3+ concentration reduce a little bit, it is possible to better the correlated color temperature uniformity and lumen efficacy of LED packages. In addition, the Mie scattering theory, Monte Carlo simulation and LightTools 8.3.2 software are employed to analyze and simulate the LED packages' structure as well as the phosphor compound.
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White LEDs, based on blue LED chips coated with a yellow emitting phosphor (YAG:Ce), have several disadvantages. In this paper, we report the improvement in CRI [Color Rendition Index] using GdAl 5 O 12 :Ce (GdAG:Ce) and related phosphors for blue LEDs. A modified combustion synthesis route using mixed fuel was used for synthesis route. By using this procedure, we formed the desired compounds in a single step. LEDs were then fabricated by coating the blue LED chips (CREE 470 nm, 300 micron) with the GdAG:Ce phosphor dispersed in epoxy resin. The CRI typically between 65~70 for the YAG:Ce based LED was improved to 87 for LEDs fabricated from the Gd(Al,Ga)G phosphors.
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