Single-phase excitation-wavelength-independent nitrogen doped graphene quantum dots for the fabrication of white light-emitting diodes (WLEDs)

At present, most white light-emitting diodes (WLED)s are modulated by mixing one or more kinds of quantum dots with a certain rare earth phosphor. However, because rare earth resources are limited, non-renewable, and expensive, it is urgent to develop a solution that does not rely on rare earths to solve the above problems. In this study, we used a hydrothermal method to fabricate nitrogen-doped graphene quantum dots (N:GQDs) using citric acid and piperazine as carbon and nitrogen sources. The N:GQDs exhibited blue fluorescence in solution under UV excitation at 365 nm, while exhibiting white luminescence in the solid state. The Commission Internationale de l’Enclairage coordinates and correlated color temperatures (CCTs) for the WLEDs based on N:GQDs are (0.28, 0.31) and 7469 K, respectively, and the WLEDs presented an outstanding color rendering index of up to 92.3, which can be used to realize the preparation of LED phosphors via single quantum dots for WLEDs, and is promising for use as backlights in lighting sources and displays.