Orange-red, green, and blue fluorescence carbon dots for white light emitting diodes

Fluorescent carbon dots (CDs) are admirable nanomaterials due to their superior optical properties and low cost. However, regulation of the emission colors in CDs for lighting device still remains a challenge. In this work, we developed a green hydrothermal method to obtain three emission colors of CDs using l-tyrosine (for blue CDs), o-phenylendiamine (for green CDs) and l-tyrosine/o-phenylendiamine mixture (for orange-red CDs). These CDs possess good water dispersibility, strong emission with high quantum yields, and excellent photostability. Furthermore, the resulting CDs were dispersed in polyvinyl alcohol (PVA) matrix to yield solid state films, where the self-quenching effect in solid state was effectively avoided. A full-color light-emitting diode was fabricated by packing the CDs-PVA composites on the top of a UV-chip, which have superior potential applications in CDs-based solid-state lighting system.