Optimization of light efficacy and angular color uniformity by hybrid phosphor particle size for white light-emitting diode

Rare Met., 2014, 33, 3, 348. https://link.springer.com/article/10.1007/s12598-013-0216-9.

In this study, small- and large-particle-diameter phosphor powders were mixed together (hybrid phosphors) to balance light efficacy and angular color uniformity and pursue optimal results. Phosphor with small-particle-diameter of 4 μm was employed and it was mixed into each large-particle-diameter phosphor of 10, 16, 22, and 26 μm, at mass percentage from 0 % to 50 % with an interval of 10 %, respectively. Remote phosphor package was adopted and overall phosphor concentration was kept constant for better comparison. Moreover, absorption coefficient μ abs, scattering coefficient μ sca and extinction coefficient μ ext of each hybrid phosphors were calculated based on Mie theory to further discuss the experiment results. Results show that, the introduction of small-particle-diameter phosphor to large one can highly improve angular color uniformity while only slightly reduce light efficacy. The optimal performance with angular color uniformity of 91.6 % as well as normalized light efficacy of 95.7 % is achieved in the white light emitting diode with hybrid phosphors consisting of 60 wt% powder of 22 μm and 40 wt% powder of 4 μm.