Tunable full-color solid-state fluorescent carbon dots for light emitting diodes

Carbon dots (CDs) as a class of new fluorescent materials have attracted numerous attention. However, the solid-state photoluminescence quenching of CDs is still a big challenge. In this work, self-quenching-resistant solid-state fluorescent CDs are achieved, which exhibit tunable full-color solid-state emission without any other additional solid matrices. These CDs were prepared via one-step microwave method using phloroglucinol and urea as sources by regulating reactant ratio and microwave power. The maximum emission of CDs gradually shifts from 445 to 643 nm, and solid-state quantum yield of five typical CDs with blue (B), green (G), yellow (Y), orange (O) and red (R) emission reaches up 48.2%, 26.0%, 18.5%, 13.7% and 5.7%, respectively. Moreover, multicolor solid-solid fluorescence mechanism of CDs is investigated. The G-, Y-, O-, R-CDs show aggregation-induced red-shift behavior, while B-CDs exhibit unique crystallization-induced emission enhancement property. Finally, CDs are utilized as phosphors combing with ultraviolet chip to fabricate multicolor and white light emitting diodes (LEDs). The obtained white LEDs exhibit an adjustable correlated color temperature (3937–8588 K) and high color rendering index (80–88). This study provides a novel guidance for developing self-quenching resistant CDs with multicolor emission.