Extremely high color rendering white light from surface passivated carbon dots and Zn-doped AgInS2 nanocrystals

In this study, highly luminescent carbon dots with diameters of 3-5 nm were synthesized via the carbonization of citric acid, and the effects of surface passivation and carbonization temperature on the optical properties were investigated. A red-shift in the emission wavelength was observed with increasing excitation wavelength, and oleylamine-capped carbon dots showed the highest quantum yield of approximately 43% when excited at 380 nm, whereas the reaction temperature had no influence on the emission wavelength and morphology of the dots. Additionally, I-III-VI AgInS2 nanocrystals (NCs) were prepared by thermal decomposition at a low temperature, and the emission wavelength was tuned by adjusting the growth temperature or introducing Zn ions, which enhanced the quantum yield up to 50%. For carbon dot application, a white LED was fabricated by combining a 380 nm UV LED with the carbon dots and Zn-doped AgInS2 NCs. White light from this LED exhibited an excellent color rendering index of greater than 95 with a warm color temperature, and demonstrated its potential for use in solid state lighting.