Spectral Re-Absorption Effect of Multi-Primary Phosphor Thin Films and Various Package Structures on the Performance of Near-Ultraviolet White LED

Abstract

We prepared blue, green and red phosphor thin films (PTFs) with different phosphor concentrations used for near-ultraviolet (NUV) LEDs respectively, and then investigated their spectral re-absorption/excitation/emission process. The functional relationship between optical powers and concentrations were established by using the exponential equation. The relationship between the spectral deformations and concentrations were evaluated by the correlation coefficient. Based on NUV LED chip, eight package structures of white LEDs were prepared. The luminous efficiency (LE) of white LED based on Blue/Green/Red@NUV laminate structure reached 85.48 lm/W, which was 27.7% higher than that of hybrid structure, correlated color temperature (CCT) was 3518K, Rf was 83, Rg was 106, and when hybrid structure thickness was reduced to one-third points, the LE increased by 21.5% to 81.36 lm/W, CCT was 4200K, Rf was 93, Rg was 101, CCT uniformity test showed that the uniformities of laminated and hybrid structures were 80.06% and 96.91% respectively. The results showed that the laminated structure was beneficial to improve the LE, while the hybrid structure had the advantage of uniformity improvement and spectrum continuity due to multi-particle scattering and spectral deformation of the phosphor.