Tunable multi-peak emission solid-state fluorescent carbon dots: Luminescence regulation mechanism and application in single-component-based LEDs

The design of solid-state fluorescent carbon dots (CDs) with multi-peak emission has become an urgent challenge to be solved with the in-depth research of CDs in LEDs. Here, one- and two-component solid-state white light CDs are synthesized by microwave-assisted hydrothermal method using the biological pollutant cyanobacteria, respectively. The solid-state fluorescence quantum yield of the one-component CDs was as high as 41.8 %, and the solid-state fluorescence mechanism of CDs is discussed to be mainly attributed to the self-quenching-resistant feature of “core-shell” structure and the reabsorption/RET-induced long-wavelength red light emission, and attenuation of the short emission wavelength. For two-component white light CDs, blue- and red-light CDs are obtained by simple dialysis separation, realizing the fluorescence tunability. The different origins of their multi-peak emission are discussed: core, edge and surface states. The synthesis yields of CDs are up to 62 %, enabling stable gram-scale production. The white- and red-light CDs are used as phosphors to fabricate fluorescent films and cold, pure, and warm white- and red-light LEDs with good resistance to photobleaching and temperature stability and CRI of 84.4, 85.7 and 61.5.