White Light Afterglow in Carbon Dots Achieved via Synergy between the Room‐Temperature Phosphorescence and the Delayed Fluorescence

Carbon dot (CD) based long‐lived afterglow emission materials have attracted attention in recent years, but demonstration of white‐light room‐temperature afterglow remains challenging, due to the difficulty of simultaneous generation of multiple long‐lived excited states with distinct chromatic emission. In this work, a white‐light room‐temperature long‐lived afterglow emission from a CD powder with a high efficiency of 5.8% and Commission International de l'Eclairage (CIE) coordinates of (0.396, 0.409) is realized. The afterglow of the CDs originates from a synergy between the phosphorescence of the carbon core and the delayed fluorescence associated with the surface CN moieties, which is accomplished by matching the singlet state of the surface groups of the CDs with the long‐lived triplet state of the carbon core, resulting in an efficient energy transfer. It is demonstrated how the long‐lived afterglow emission of CDs can be utilized for fabrication of white light emitting devices and in anticounterfeiting applications. Carbon dots exhibit a bright white‐light room‐temperature afterglow, which is a result of a synergistic effect between the phosphorescence of the carbon core and the delayed fluorescence of the surface CN moieties.