Excitation-Independent Dual-Color Carbon Dots: Surface-State Controlling and Solid-State Lighting

Long-wavelength orange-red emissions of carbon dots have recently attracted great attention due to their wide applications. Although it is possible to achieve long-wavelength luminescence by varying the incident excitation wavelength, excitation-independency is highly desired in terms of both practical applications and understanding emission mechanisms. In the present work, carbon dots with excitation wavelength independent orange and blue dual-color emissions were synthesized by a facile solvothermal route using p-phenylenediamine as carbon source and formamide as solvent. Structural and spectroscopic characterizations indicated that N- and O-related surface state controlling via modifying reacting temperature/time was responsible for the dual-color emissions of carbon dots. Moreover, carbon solid film, retaining original orange emissions, was fabricated to explore its possible application as color converter in solid-state lighting. Impressively, by combining orange carbon film and yellow phosphor-in-glass with an InGaN blue chip, light-emitting diode devices with improved color-rendering index and correlated color temperature were successfully constructed.