Multicolor carbon dots assembled polyvinyl alcohol with enhanced emission for white light-emitting diode

Red carbon dots (R-CDs), yellow-green carbon dots (Y-CDs) and blue carbon dots (B-CDs) were successfully synthesized by one-step hydrothermal method using o-phenylenediamine and dopamine hydrochloride as raw materials by adjusting the pH of the reaction solvent. The Fourier transform infrared (FT-IR) spectra, X-ray photoelectron spectroscopy (XPS) spectra and optical properties of CDs show that these three CDs have similar types but different contents of functional groups, resulting in different fluorescence emission. R-CDs and Y-CDs compound with polyvinyl alcohol (PVA) to form bright R-CDs/PVA and Y-CDs/PVA phosphors, while B-CDs/PVA phosphors have weak fluorescence. Compared with R-CDs and Y-CDs solution, the fluorescence emission of the phosphors was significantly enhanced for the matrix inhibits the process of non-radiative transition. Based on the thermostability and broad emission peaks of CD-based phosphors, light-emitting diode (LED) was fabricated using R-CDs/PVA and Y-CDs/PVA phosphors as fluorescent material. The prepared LED exhibits white light with a color coordinate of (0.32, 0.33), correlated color temperature (CCT) of 6067 K and color rendering index (CRI) of 78.2. The environmental-friendly CD-based white light-emitting diode (WLED) was successfully fabricated.