A single-phase heteroatom doped carbon dot phosphor toward white light-emitting diodes

Abstract

Nitrogen doped carbon dots (N-CDs) with a quantum yield (QY) of 67.06% and nitrogen sulfur co-doped carbon dots (NS-CDs) with a QY of 9.80% were prepared by a hydrothermal method using citric acid monohydrate as the carbon source and ethylenediamine or thiourea as additives, respectively. The morphology, structure and optical properties of the as-obtained samples were investigated. Notably, the double-bond between the carbon and sulfur antagonized the promotion of QY. Compared with NS-CDs, N-CDs exhibit a high QY, broad and bright light under ultraviolet illumination that would be worth utilizing in a phosphor based on a UV chip. For practical applications, white light-emitting diodes were fabricated by combining the N-CDs/optical encapsulant mixture with a UV chip, which emitted near white light with color coordinates of (0.38, 0.42) and a correlated color temperature of 4290 K.