Influence of silver nitrate in obtaining highly luminescent sodium-doped carbon dots for white light emitting diodes

Abstract

Luminescent metal-doping carbon dots (CDs) possess excellent optical properties for light-converting phosphors of white light emitting diode (LED). However, the photoluminescence quantum yields (PL QYs) of CDs still suffer from the trapping defect at the surface of CDs which may generate the detrimental nonradiative recombination centers. Herein, we developed an N doping method to enhance blue light emission of Na+-doped CDs via a modified solid-state reaction, using silver nitrate as nitrogen source. The blue PL intensity form Na+-doped CDs is improved by the increasing molar ratio of silver nitrate precursor. The obtained Na+ and N co-doping CDs exhibited 5-fold enhancement of PL intensity with a PL QYs up to 24% as compared to their undoped counterpart. Based on the temporal evolution of PL and surface structure characteristics, it suggested that the improvement of PL QYs derived from the elimination of the trapping defects at the surface of Na+-doped CDs. This is realized by the introduction of nitrate groups and Ag+ ions, which can reduce the formation of hydroxyl radicals related nonradiative recombination centers. Furthermore, the Na+ and N co-doped CDs is applied with (Gd,Y)3(Ga,Al)5O12: Ce3+ yellow phosphor on a commercial UV-LED chip, achieving strong cold white emission. Our finding provides a new idea to enhance blue PL QYs of Na+-doped CDs for their further potential applications in optoelectronic devices.