Solvent-free and High-yielding Synthesis of Highly Efficient Red-emitting Carbon Dots and Their Application in White Light Devices

Highly efficient red-emitting carbon dots (R-CDs) were synthesized on a large scale by a solvent-free method using o-phenylenediamine, 2,5-diaminobenzene sulfonic acid and aluminum trichloride as raw materials. The obtained R-CDs are approximately 2.4 nm in diameter, have a nitrogen content of 13%, and consist of a highly graphitized carbon core coated with abundant functional groups. Under light illumination with different wavelengths, the R-CDs in ethanol solution show an excitation-independent red emission at 704 nm, with a quantum yield (QY) as high as 22%. By virtue of their excellent optical properties, an UV-excited carbon dots-based pure white light emitting diode (WLEDs) was successfully constructed with a color coordinate of (0.33, 0.33) , which is very close to that of natural sunlight. This study paves a new path for the large scale preparation of R-CDs with high QY, and broadens their application in luminescent devices.