Effects of phosphor’s thickness and concentration on performance of white LEDs

The state of phosphor will greatly influence the packaging performance such as luminous efficiency, quality of white light and color uniformity. The analysis presents that the small variations of thickness and concentration could significantly influence the light extraction efficiency and the correlated color temperature (CCT). With the increase of thickness and concentration, the light extraction efficiency is reduced, and the yellow blue ratio is increased, which means the color will tend to be warm white or yellow light. The reflector has slight influence on the performance, and the remote phosphor location is a better choice in packaging. When the thickness and concentration are determined, the manufacture tolerance for the variation are in the range of plusmn 0.02 mm for thickness and plusmn 5 mm-1 for concentration.