Regulation of particle size and surface state to realize multicolor solid carbon dots for white light emitting diodes

Multicolor solid-state carbon dots (MSCDs) with superior photothermal stability and tunable fluorescence exhibit significant potential for applications in light-emitting diodes (LEDs) and optoelectronic devices. However, the development of a facile and efficient synthetic method using simple raw materials remains a challenge. In this study, blue (B), green (G), and red (R) emissive carbon dots (B-CDs, G-CDs, and R-CDs) are synthesized by varying pre-treatment methods and raw material ratios, using 1-(1-Naphthyl)ethylamine (1-NEA) as the carbon source and boric acid (BA) as the matrix. B-CDs, prepared via freeze-drying pre-treatment in a nitrogen (N2) protective atmosphere, exhibits the smallest particle size and the largest emission bandgap. Conversely, G-CDs and R-CDs display larger particle sizes, with R-CDs having the smallest emission bandgap due to differing raw material ratios that introduced distinct surface state defects. These variations in emission bandgaps result in diverse fluorescence emissions under ultraviolet (UV) light excitation. Leveraging the excellent luminescent properties, white LEDs (W-LEDs) are fabricated by combining and coating the CDs onto a 400 nm LED chip. The resulting W-LEDs demonstrate outstanding photothermal stability and a high color rendering index (CRI) of 90-93 during prolonged operation. This work provides valuable insights for the application of MSCDs in W-LED technology.