White LED Illumination Principles
There are three ways to make white LED.
(1) One is to use individual LEDs that emit three primary colors– red, green, and blue, and then mix all the colors to produce white light.
(2) Use a tri-phosphor material to convert monochromatic light from UV LED to broad-spectrum white light, much in the same way a fluorescent light bulb works.
(3) Use a yellow phosphor material to convert monochromatic light from a blue LED to broad-spectrum white light, which is the most efficient way.