Investigation on the influence of phosphor particle size gradient on the optical performance of white light-emitting diodes

In this study, the influence of phosphor particle size gradient on the optical performance of white light-emitting diodes (WLEDs) was investigated. Three multi-size phosphor layer structures with different size gradients were proposed. The YAG:Ce phosphor particles of 3 μm and 13 μm were configured at three different locations to form the size gradient. Both simulation and experimental investigations were performed to characterize the optical performance of WLEDs. In the simulation, the proposed WLED packages were modeled by a ray-tracing algorithm, where optical constants were obtained from the Lorenz-Mie theory. In the experimental investigation, a double dispensing-curing method was employed for the fabrication of dual phosphor layer structures. The radiant power, luminous efficacy, correlated color temperature (CCT) as well as angular color uniformity (ACU) were used as the key criteria to evaluate the optical performance.