Color-Tunable Carbon Dots Possessing Solid-State Emission for Full Color Light-Emitting Diodes Applications

In this paper, a unique strategy is proposed to modulate fluorescence color of carbon dots (CDs) under both aqueous solution and solid state for bright multicolor light-emitting diodes (LEDs) applications. We report facile synthesis of dual-peak-emissive CDs with self-quenching-resistant character under solid state through hydrothermal method, and investigate the origins of dual-peak emission for the first time. In addition, based on the unique dual-peak-emissive phenomenon, acid mediated PL behaviors were realized by changing the pH value of hydrothermal precursors. We realized the color-tunable fluorescence under aqueous solution from blue (B-CDs) to yellow-green (YG-CDs) color and solid state from yellow to orange red color. The changed PL behaviors are attributed to the more conjugated structure inside CDs due to elevated carbonization degree. Furthermore, the red-shifted fluorescence from aqueous solution to solid state is ascribed to supramolecular cross-linking between adjacent particles. Thus, by manipulating the supramolecular cross-linking degree of YG-CDs in PVA, a series of luminescent blue-shifted CDs/PVA composite phosphors were obtained. Finally, we fabricate the almost full-color and white color LEDs with decent performances, which indicate their potential for solid-state lighting applications.