Journal of Optoelectronics and Advanced Materials
The applications of white light-emitting diodes (WLEDs) have increasingly been popular in today's society, yet color inhomogeneity and poor luminous flux are restricting their development. In this paper, a structure of double-layer phosphor package of white LED is proposed to improve color uniformity and luminous flux, in which the green phosphor layer SrBaSiO4:Eu2+ was placed above the yellow phosphor layer YAG:Ce3+. The SrBaSiO4:Eu2+ concentration added must be modified until the highest luminous flux and chromatic homogeneity are achieved. Five similar WLEDs with different color temperatures ranging from 5600 K - 8500 K were used in this study. The results show that the greater the SrBaSiO4:Eu2+ concentration, the higher the luminous flux due to the increased green light component in WLEDs. However, a slight decrease in color rendering index and color quality index occurred when the SrBaSiO4:Eu2+ concentration increased excessively, according to the simulations and Monte Carlo calculations. This paper is a vital reference to the fabrication of WLEDs with higher illumination efficiency and color uniformity of the phosphor structures.
