Efficient and stable white fluorescent carbon dots and CD-based glass thin-films via screen-printing technology for use in W-LEDs

Abstract

White fluorescent carbon dots (WCDs) were synthesized by combining red carbon dots (RCDs) with ethanol or N-(β-aminoethyl)-γ-aminopropyl methldimethoxy silane (AEAPMS) for the first time. Interestingly, the RCDs have excitation-independent behavior while the WCDs exhibit excitation-dependent behavior. These WCDs emit bright white light with quantum yields (QYs) of 50.8% and 57.1%. Solvatochromism effects of the CDs were ascribed to the intermolecular charge transfer between the CDs and solvents. The solvents further increase the charge carrier density and induce the charge transfer. Investigation of the white fluorescence mechanism of the CDs revealed a multilevel emissive recombination channel, which might be from the distribution of diverse surface-state PL centers. Additionally, because the latter WCDs exhibit excellent optical properties and a great film-forming ability, workable white CD-based glass thin-films were constructed using facile screen-printing technology. Finally, the as-fabricated white light-emitting diodes (W-LEDs) exhibited an optimized color coordinate (CIE) of (0.33, 0.34), color rendering index (CRI) of 51 and correlated color temperature (CCT) of 6735 K. Therefore, the WCDs reveal the strong feasibility of being used for lighting and displays.