Optical Analysis of Phosphor's Location for High-Power Light-Emitting Diodes

High-power-light-emitting-diode (LED) packaging is crucial for the development of solid-state lighting. Phosphor's location could affect the LED packaging performance such as light extraction and correlated color temperature (CCT). This paper systematically analyzes first the effects of phosphor's location on LED packaging performance. A two-light-source step computation method based on the Monte Carlo theory is developed, and five different optical structures are discussed. Results show that the location of phosphor has small impact on light extraction but could greatly affect CCT. Remote phosphor location presents higher light extraction than proximate phosphor location. However, the increase is slight, and too remote location could reduce light extraction. A convex phosphor layer has higher light extraction but lower yellow-blue ratio than a plane phosphor layer. Considering the significant variation of CCT, it is suggested that an optical structure with plane and remote phosphor location should be a suitable choice for LED packaging.