Single Solid‐State Emissive Carbon Quantum Dots for Multicolor, Bright and Efficient Electroluminescent Light‐Emitting Diodes

Color‐tunable electroluminescent light‐emitting diodes (LEDs) based on quantum dots (QDs) are rapidly emerging as a key technology for next‐generation full‐color displays and solid‐state lighting. However, achieving broad color tunability in LEDs that utilize a single QD emissive material continues to pose significant challenges. Here, we present the first example of bright, multicolor electroluminescent LEDs with tunable emission peaks spanning from 535 to 640 nm, utilizing a new type of single red solid‐state emissive carbon quantum dots (R‐SSCQDs). Unlike conventional CQDs, which often exhibit weak or negligible emission in solid‐state form, R‐SSCQDs demonstrate bright red emission in solid state and green emission in diluted state. Experimental investigations and theoretical calculations reveal that the unique non‐planar spatial structure and significant steric hindrance of R‐SSCQDs effectively suppress π‐π stacking, resulting in efficient solid‐state fluorescence emission. By adjusting the weight ratios of R‐SSCQDs doped in host materials, we showcase bright, efficient and multicolor CQD‐based LEDs that emit green, yellow, orange, and red light, achieving a record‐high luminance of 15,834 cd m‐2 and current efficiency of 10.3 cd A‐1. This work presents a straightforward and universal strategy for creating efficient solid‐state emissive CQDs, showcasing significant potential for color‐tunable LED applications.