Polymerized Carbon Dots with Broad Emission and Suppressed Aggregation-Caused Quenching Effect Toward Electroluminescent White Light-Emitting Diodes

Carbon dots (CDs) possess intrinsically broad emission spectra, making them suitable for modulating high-quality white light-emitting diodes (WLEDs). However, the chief technical challenge in applying CDs to WLEDs is the aggregation-caused quenching (ACQ) effect. A common solution is polymer post-modification on the surface of CDs, which is a low-yield, hard-to-purified, and complicated process. Herein, polymerized CDs with broad emission (full width at half maxima, FWHM = 187 nm) are synthesized via a one-step solvothermal method. The obtained polymerized CDs display excellent solution-processed and film-forming capabilities, with absolute photoluminescence quantum yield as high as 4.7% in thin film state, creating a firm foundation for assembling solution-processed WLEDs. Moreover, the polymerization steps of CDs are analyzed and described in detail. The polymer chains prevent ACQ and create new energy levels, resulting in the broad emission of CDs in an aggregated state. Subsequently, WLEDs are fabricated using polymerized CDs as the single active emitting material. The optimal device achieves the maximum brightness of 337.50 cd m-2 and FWHM of 242 nm, covering nearly the entire visible spectral window. The results present a new approach to obtaining polymerized CDs and further fabricating WLED with a straightforward, cost-effective method. The surface of obtained carbon dots spontaneously forms electron-rich polymer chains to resist aggregation-caused quenching. The crosslink-enhanced emission effect entitles the obtained carbon dots to absolute PLQY of 4.7% and FWHM of 187 nm. Bright white organic light-emitting diodes with broad FWHM of 242 nm are realized by doping polymerized carbon dots into poly(9-vinylcarbazole) as a single guest material. image