The Effects of TiO2 Diffuser-Loaded Encapsulation on Corrected Color Temperature Uniformity of Remote Phosphor White LEDs

Abstract

With the development of high-efficiency and high-power LEDs, they have become the most energy-efficient and environmentally friendly artificial light source. Phosphor-converted white LEDs are currently mainstream in the market. The remote phosphor is an effective way to enhance the conversion efficiency and lifetime of phosphor-converted LEDs. For applications of high-quality lighting and LCD backlights, the uniformity of angular correlated color temperature (CCT) is very important. This report explored a remote phosphor white LED with low angular CCT variance and high luminous efficiency by using TiO2 diffuser-loaded encapsulation. Experimental results revealed that for the TiO2 diffuser-loaded encapsulation remote phosphor white LED, the angular color uniformity could be improved by 31.82% and the luminous flux by 8.65%. Moreover, the mean CCTs of the TiO2 diffuser-loaded encapsulation and non-diffuser remote phosphor white LEDs were similar at a driving current of 350 mA. Finally, we showed that incorporating the TiO2 diffuser into the phosphor layer of the remote phosphor white LEDs, does not influence the reliability of the LED.

Color Conversion Light-Emitting Diodes Based on Carbon Dots: A Review

“…The difference between the refractive index of the diffusers and of the encapsulant causes scattering from the diffusers, which uniformizes the chromaticity distribution of the emissive radiation. This has also been confirmed by working with a remote phosphor WLED configuration: using TiO 2 as the encapsulant, the luminous flux significantly improved by 8.65% [ 132 ]. The same effect has been tested with CDs and TiO 2 nanoparticles dispersed in a silicone encapsulant; here, the luminous intensity is increased by 31% for a concentration of TiO 2 nanoparticles of 0.05 wt%.…”

Selective Coating of White Silicone to Improve the Optical and Thermal Characteristics of White LED Packages

“…The results show that regardless of the type of the packages, the EL intensity increases with increasing current. [12][13][14]16,24 Figure 6 shows the far-field emission patterns obtained from the blue and white LED packages fabricated with the uncoated and coated Zener diodes, which were operated at 65 mA. For the blue and white LED packages with the uncoated and coated Zener diodes, the view angles were measured along the two orthogonal directions.…”

“…13 In this study, we also investigated the effect of TiO 2 particles-mixed white silicone on the output performance of middle-power LED packages. However, unlike the previous works, [12][13][14][15][16] where the surrounding region of chip or the plastic reflector inside the package was coated by white silicone to improve the luminous flux, the TiO 2 particles-mixed white silicone covered only Zener diode bonding part. To investigate the reliability, high temperature/high humidity and high temperature operation tests were performed.…”

“…It was reported that TiO 2 having high refractive index was often mixed with epoxy to improve the output performance of LEDs. [12][13][14][15][16] For example, surfactant-coated TiO 2 nanoparticles were included in epoxy for LED encapsulation and theoretical light-extraction enhancement was simulated to be more than 50% compared with conventional LED packages. 12 It was also found that for chip-on-board packaging LEDs, the insertion of a TiO 2 nanoparticles/silicone composite layer below the major encapsulation layer (phosphor and silicone composite) resulted in 24% higher light extraction compared with those with only main encapsulation layer.…”

Novel optical applications inspired by the Morpho butterfly’s coloration: technology transfer from reflection to transmission

“…Furthermore, color temperature uniformity can be another issue in diffuser-loaded LEDs. 45) In the end, even if the spectrum is identical to the Sunlight, it is far from an ideal and natural diffused light source. Therefore, even if the conventional luminous system can be used in a showroom where only a part of the light is emphasized, it cannot be used for various applications such as appraisal.…”