Design optimization and experimental verification of white-light-emmiting diodes using multiple phosphor films

White light-emitting-diodes (LEDs) are known as a new generation lighting source. Using a blue LED with a phosphor layer which is excited by blue light and down-converting to the second light, such m yellow light, white light can be produced. Using a one-dimensional mathematical model, we can describe the light propagation by simple absorption, conversion, and reflection terms. We use a multiple phosphor film coating method to determine the coefficient of the model, followed by analysis to determine the optimum phosphor layer LED package. With a phosphor layer plus a yellow light reflector, the white light extraction efficiency could be above 0.9 relative the conventional package's 0.6-0.8.