Nickel-doped carbon dots with enhanced and tunable multicolor fluorescence emission for multicolor light-emitting diodes

Carbon dots (CDs) are a new type of carbon-based fluorescent nanomaterials, which have received a lot of interest because of their excellent properties, simple synthesis and wide applications. However, facial and fast synthesis of CDs with tunable multicolor emission that can be used for lighting still remains a challenge. Here, through a simple one-step solvothermal method, nickel-doped CDs with tunable fluorescence emission are successfully prepared. By optimizing the experimental conditions, fluorescence emission of the as-prepared CDs can be adjusted within a certain wavelength range (513 nm-612 nm), that is, from green to red. The particle size of the CDs also increases from 2 nm to 8 nm. The introduction of Ni can successfully enhance the fluorescence intensity and cause an obvious redshift. In addition, by mixing polyvinylpyrrolidone (PVP) with the multicolor nickel-doped CDs (Ni-MCDs), the self-quenching effect of solid-state fluorescence can be effectively avoided. Based on this, green, yellow and red light-emitting diodes (LEDs) with high performance can be constructed by integrating CDs/PVP composites with different colors on top of the UV chip, demonstrating their superior potential for solid-state lighting applications.