SiO2 Aerogel Mixed in Silicone Encapsulant to Improve Chromaticity Coordinate Inconsistencies of WLEDs

Porous SiO2 aerogel and yttrium aluminum garnet (YAG) phosphor is simultaneously mixed in silicone encapsulant, which can reduce the dispersion of color temperature and chromaticity coordinates of white light-emitting diodes (WLEDs) due to phosphor sedimentation after dispensing. The concentrations of YAG phosphor and SiO2 aerogel in the silicone encapsulant of WLEDs were mixed at 10 wt% and 1 wt%, respectively. Compared with the WLED without mixing SiO2 aerogel, the average correlated color temperature (CCT) difference in the light emitting angle range
$- 60^{\circ }\sim 60^{\circ }$
decreased from 310K to 221K to obtain an 89K improvement. The average CCT of WLEDs along the central axis of luminescence was also reduced from 5450K (±320K) to 5040K (±109K) and the average luminous flux increased by 4.9%. The mixing of SiO2 aerogel in the silicone encapsulant can reduce the dispersion of the axial average CCT distribution of WLEDs due to different dispensing sequences, and the average CCT standard deviation is reduced from 168K to 64K to obtain a 62% improvement. The chromaticity coordinate distribution of WLEDs also converges from MacAdam ellipse’s 5-step to 3-step. Mixing SiO2 aerogel in the silicone encapsulant can improve the distribution consistency of CCT and chromaticity coordinates of WLEDs using the dispensing process.