Comparison between SEPs of CaCO₃ and TiO₂ in phosphor layer for better color uniformity and stable luminous flux of WLEDs with 7,000 K

Abstract

CaCO3 and TiO2 are proposed in this study as particles for scattering enhancement (SEPs) of phosphor-converted white light-emitting diodes (pc-WLEDs). The use of these two SEPs for scattering improvement enables boosting of the color homogeneity of the WLED devices. Each SEP is mixed with YAG:Ce3+ and silicone composition to examine their optical influences and performances on the high-power WLED packages with 7,000 K color temperature (CT). Miescattering theory is applied to calculate and investigate the scattering elements – scattering coefficients, anisotropic scattering, the reduced scattering, and scattering amplitudes – at the wavelengths of 450 nm and 550 nm. The results exhibit that TiO2 and CaCO3 considerably promote higher color uniformity and color-deviated reduction, respectively. The obtained results could be primarily attributed to the significant improvement in the scattering properties of the structure. Additionally, the effects of the presented scattering enhancement on luminous efficiency are displayed. The reduction in lumen output is observed to have a close connection with the concentration and particle size of TiO2 and CaCO3, which means that control must be exercised over these factors when utilizing these SEPs for WLED fabrication.