Abstract
White-light-emitting diodes (WLEDs) are currently the main white light sources for lighting, traffic light or backlighting of displays due to their long lifespan (50,000 h), brightness (800 lm) and luminous efficacy (150 lm·w-1), low power consumption (8.5 W), coast-benefit (60 dollars over 20 years of use) and environmentally friendly properties compared to incandescent and fluorescent l…