Investigation and Optimization of Phosphors for Ultraviolet Light-emitting Diodes
Date Issued
2011
Date
2011
Author(s)
Chu, Cheng-I
Abstract
White light emitting diodes (WLEDs) are the key lighting devices of the 21st century with high luminous efficiency, durability, low pollution, small size etc. Ultraviolet light-emitting diode pumps red, green and blue phosphors to produce white light which have high color rendering index, color tenability, least color shift with temperature, and fewer barriers from patents. This device has great potential to form white light-emitting diode.
In our research, we develop the phosphors based on Ba3Si6O12N2 and SrAlO4 hosts. Ba3Si6O12N2 were synthesized by gas pressure sintering and nonstoichemirstry. This oxonitridosilicates phosphor has advantages of thermal stability, moisture resistance etc. We characterize energy transfer mechanism and optical properties of Ba3Si6O12N2 doping Eu, Ce or Tb. Ba3Si6O12N2:Eu produce high intensity green light emission (522 nm) and enhanced photoluminescence 30% by seed mediating method and acid solution purification. Ba3Si6O12N2 doped Ce are blue light emission and there is dipole-dipole energy transfer from Ce to Eu. In Ba3Si6O12N2 doped Tb, the vacuum ultraviolet photoluminescence spectrum show charge transfer between Tb and the host which enhance 5D3→7FJ blue light emission.
In SrAl2O4 host co-doped with five factors: Eu2+, Ce3+, Dy3+, Li+ and H3BO3, that is long-lasting luminescence material. We investigate these compounds based on a combinatorial approach in conjunction with the Taguchi method which reduce experiment times and analysis effect of each factor via Taguchi method. The results are conforming to previous studies and physics principle. This study are the first one demonstrates that the utility of the combinatorial approach for evaluating the effect of factors on an objective property and estimating the expected performance under the optimal conditions can be improved by the Taguchi method. These studies were published in “Luminescence” as a cover letter and feature article.
We provide a new method to optimized phosphor via combinatorial approach with Taguchi method, and investigate optical properties and energy transfer mechanism of Ba3Si6O12N2 and SrAlO4 hosts doped activators. Finally UV-LEDs were packaged with Ba3Si6O12N2: Eu and commercial phosphors to produce white light. The white light has high color rendering index (Ra = 96.2) and low color temperature (3683 K). It has a great potential as lighting source.
Subjects
phosphor
oxonitridosilicates
combinatorial chemistry
Type
thesis
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