Matrix-free, color-tunable carbon quantum dots with solid-state emission for white LEDs

Solid-state photoluminescence quenching poses a major challenge for carbon quantum dots (CQDs) in optoelectronic applications. This work presents a facile one-step microwave synthesis of self-quenching-resistant, color-tunable CQDs from phloroglucinol and urea without requiring external matrices. By precisely controlling reactant ratios and microwave power, we achieved tunable photoluminescence from blue to yellow (395-590 nm) through an aggregation-induced redshift mechanism. The resulting CQDs exhibited exceptional solid-state quantum yields of 45.2% (blue) and 52.0% (yellow), along with remarkable photostability (> 90.5% retention after 90 min UV exposure). Leveraging these properties, we fabricated dual-color and white light-emitting diodes that demonstrated promising performance, including a maximum luminous efficacy of 55.8 lm/W, color rendering index of 72, and excellent operational stability (85% luminous flux retention after 120 min). This matrix-free approach effectively overcomes solid-state quenching and positions CQDs as promising materials for advanced solid-state lighting technologies.