A novel chip-on-board white light-emitting diode design for light extraction enhancement

In this study, in order to resolve the low light extraction issue of chip-on-board light-emitting diodes (COB LED), the phosphor layers in COBs were molded into a pattern of cavity arrays to minimize the trapped radiant power by total internal reflection (TIR). Monte-Carlo ray-tracing simulation was performed for extraction efficiency optimization with the same color coordinates (x, y). It was found in the simulation that, with the increase of the top diameter and the depth of cavity arrays, the light extraction efficiency may increase. Furthermore, with the increase of the bottom diameter of cavity arrays, the phosphor consumption could be reduced. The present study reveals the relationship between the light emitting structure of phosphor layer and the light extraction efficiency. This research provides a useful design guideline for the optimization of LED optical performance.