Carbon dots synthesized from citric acid, urea, and N-Methyl-2-pyrrolidone system for feasible applications in photoluminescence and electroluminescence

Fantastic carbon dots (CDs) with solution-processing, eco-friendliness, and scalable manufacturing receive giant attention in luminescence. Herein, we demonstrate solution-processed CDs synthesized from citric acid, urea, and N-Methyl-2-pyrrolidone system with a microwave-assisted method. It offers rapid synthesis (< 10 min), good dispersibility, acceptable quantum yield (27.8%), graphitic carbon core, and uniform particle size. With CDs-doped polyvinylpyrrolidone as a composite fluorescent layer, the 365-, 395-, 410-, and 460-nm excitation gives strong photoluminescence and large full width at half maximum (~ 150 nm). The 460-nm excited LED gives 480,812 cd m⁻² luminance and 43.0 lm W⁻¹ power efficiency, which are superior to the counterparts. With CDs-doped poly(N-vinyl carbazole) (PVK) as an emitter, the electroluminescent LED achieves a maximum luminance of 866 cd m⁻² and voltage-dependent color tunability from violet emission of PVK at low voltages to near white emission of CDs, PVK, and the PVK/CDs interface at high voltages. This work highlights potential CDs synthesis with efficient and wide emission, opening up novel approaches for assembling high-performance photoluminescent and electroluminescent LEDs.