Enhancing color homogeneity and luminous flux of WLEDs with double-layer phosphor configuration


T. T. TRANG, P. X. LE, H. Y. LEE, N. D. Q. ANH

Source title

Journal of Optoelectronics and Advanced Materials

Publication year

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.