Phosphor size dependence of lumen efficiency and spatial CCT uniformity for typical white LED emitters

Phosphor particle size effect on both lumen efficiency and angular uniformity of correlated color temperature (CCT) is studied for three types of phosphor converted white LEDs using Monte Carlo simulation tool. It is demonstrated for the first time that the size effect is non-monotonic and exhibits minima in the sub-micron size range. In particularly, the minimum lumen efficiency exists at the particle size parameter (πd/λ) around 6, where, however, also lies in the relatively low CCT uniformity. Moreover, the simulation results are verified by an analytical model developed for the estimation of critical particle size. Finally, this study provides important technical implication for the selection of phosphors in WLED manufacturing and development of phosphor materials for WLED applications.