CQD-LEDs with High Colour Rendering Index

Abstract

Quantum dots (QD), which is considered the ideal candidate of third generation semiconductor lighting, has the advantages of high quantum yield, adjustable emission wavelength and narrow full width at half maxima (FWHM), thus it is an ideal choice as the colour converting materials for LEDs. InGaN LEDs are the main choice of solid-state lighting, which is always applied with Ce-doped yttrium aluminum garnet (YAG: Ce3+) yellow phosphor to achieve white light. However, white light achieved by this method has a low colour rendering index (CRI), mainly because of the missing of red spectral components in YAG: Ce3+, thus the CRI is lower than 80 and the correlated colour temperature (CCT) is always above 6500K. In order to increase the CRI of white LEDs, in this paper, we fabricated yellow CQDs and applied it on blue LED chips, red QD films were also used to increase the CRI of our white LEDs. The result shows that the white LEDs with yellow CQDs and red QD films has a max CRI of 94.3 at a driving current of 70mA, the Commission International de L'Eclairage (CIE) chromaticity coordinates are (0.325, 0.3435), and the CCT is 5832K, which is white light with high CRI and can be used in indoor lighting.