Effects of BaSO<sub>4</sub> nano-particles on the enhancement of the optical performance of white LEDs

Abstract

The usage of BaSO 4 nanoparticles on WLEDs luminous flux and color uniformity improvements have been analyzed and demonstrated in this manuscript. The mixture of BaSO 4 and silicone placed on the yellow phosphor layer benefits the internal light scattering and thus enhances the angular correlated color temperature (CCT) homogeneity. Specifically, the blue-light intensity at large angles tend to increase and results in light intensity discrepancy, which can be corrected with added BaSO 4 . In addition to this, the BaSO 4 -silicone composite modifies the refractive index of the air-phosphor layer interface to an appropriate value, and thus, the luminous efficiency increases. The results show that the CCT deviations is reduced by 580 K, from 1000 K to 420 K, within the angle range from -70 0 to +70 0 with BaSO 4 in the phosphor structure. The increase in luminous flux is also recorded by 2.25%, in comparison with that of the non-BaSO 4 traditional structure, at the 120-mA driving current. Hence, integrating BaSO 4 nanoparticles into the remote phosphor structure can contributes to the enhancement of both lumen output and CCT uniformity.