Yellow-Emissive Carbon Dots with High Solid-State Photoluminescence

Carbon dots (CDs) present an enticing prospect for a variety of optical applications relying on their high photoluminescence (PL) quantum yield (QY). Herein, the synthesis, optical properties, structural characterizations, density-functional theory (DFT) calculations, and potential applications of yellow-emissive CDs (Y-CDs) with ultra-high PL QY are reported. Solvothermal treatment of citric acid and urea in toluene, followed by column chromatography, produces Y-CDs exhibiting excitation-independent PL emission at 553 nm with a high solution PL QY of 92%. A variety of optical and structural characterizations and DFT theoretical calculations are implemented to confirm the general structure and fluorescence origin of Y-CDs, conjugated sp²-carbon domains (fused rings) with edge groups. Significantly, transparent Y-CDs/acrylic resin films with strong solid-state emissions are fabricated. The Y-CD films exhibit a high fluorescence with PL QY of 98%, good PL stability (no PL variation under continuous irradiation for 180 h), and large Stokes shift (129 nm). The potential applications of Y-CDs for luminescent solar concentrators as well as yellow phosphors for lighting are also demonstrated. These findings thus promote the development of high-performance CDs and their optoelectronic applications.