Carbon dots (CDs) have attracted a lot of attention because of their tunable emission wavelength, high photobleaching resistance, and environmental friendliness. However, they suffer from aggregation-induced quenching in the solid state, which limits their application in solid-state fields. In this work, yellow-and orange-emissive N, B-codoped CDs (y-NB-CDs and o-NB-CDs) with highly efficient solid-state fluorescence and dual emission were achieved by a facile one-step microwave method. The obtained y-NB-CDs in the powder state show bright yellow fluorescence with a high solid-state QY of 39.0% and typical dual emission peaks at 484 and 565 nm. The as-synthesized o-NB-CDs in the powder state exhibit bright orange fluorescence with a high solid-state QY of 31.1% and dual emission at 484 and 585 nm. After systematically studying the effect of N, B-codoping on the solid-state fluorescence of NB-CDs, we demonstrate that the hydrogen bond between B−OH on the surface of the NB-CDs can inhibit the direct contact of nanoparticles, and a high content of graphitic N in NB-CDs can increase the probability of the radiative process of the aromatic domains, both of which trigger high-efficiency solid-state fluorescence of NB-CDs. This finding provides a general and efficient method for highly emissive solid-state CDs. In addition, N, Bcodoping can also give NB-CDs dual emission in the short-wavelength and long-wavelength regions, ascribed to the carbon core and surface defect state, respectively. Finally, y-NB-CDs were demonstrated as a phosphor to prepare a near white light-emitting diode with a color rendering index of 84 by combining them with an ultraviolet chip.

Zinc oxide (ZnO) is one of the most extensively used electron-transporting layers (ETLs) in organic solar cells. However, owing to numerous surface defects and mismatched energy bands with the photoactive layer, light-soaking process is usually required to achieve a high device performance for the ZnO-based cells. Herein, we reported the synthesis of N,S-doped carbon quantum dots (N,S-CQDs) by a simple hydrothermal treatment using ascorbic acid and ammonium persulfate as reagents. As characterized by high-resolution transmission electron microscopy and X-ray diffraction, the synthesized CQDs were found to be 2−7 nm in dimensions, having a graphite-structured core and amorphous carbon on the shell. Fourier transform infrared and X-ray photoelectron spectroscopy analyses confirmed that these CQDs are highly nitrogen-and sulfur-doped, which leads to efficient (with a quantum yield of 33%) downconversion and excitation-dependent photoluminescence character. Application of these N,S-CQDs as surface modifier for ZnO layer in inverted organic solar cells was investigated. Results indicate that the cells with N,S-CQDs-decorated ZnO ETL showed higher power conversion efficiency without S-shaped kink in the current density−voltage curves. The performance improvement and the elimination of light-soaking effect for ZnO:N,S-CQDs cells are attributed to the ZnO surface defect passivation by N,S-CQDs, as confirmed by fluorescence spectroscopy and scanning Kelvin probe microscopy. The cells with N,S-CQDs-modified ZnO ETL showed a high power conversion efficiency of 9.31%, which is higher than the reference ZnO cells. The current work provides a feasible way to achieve shell element-doped CQDs for specific application in organic electronic devices.

To clarify the chirality mechanism of chiral CQDs prepared by l-/d-tryptophan, the chirality origin in CQD structure was revealed.

Carbon dots synthesized by a microwave-assisted hydrothermal method exhibit efficient solid-state luminescence for white light-emitting devices.

The synthesis and luminescence origin of multicolour long wavelength CQDs and solid state luminous red-green-blue CQD films for CQD phosphor-based WLEDs with a high CRI and an adjustable CCT.