Heteroatom‐Doping and Conjugation‐Extension Enable Ultrahigh‐Bright Full‐Color Carbon Quantum Dots for Tunable Liquid‐State Lasers and 3D Printing

Carbon quantum dots (CQDs) represent a novel solution-processable gain material with significant potential to replace conventional nano-luminescent materials such as organic molecules, quantum dots, and perovskites. However, the relatively low fluorescence brightness (FB) and photoluminescence quantum yield (PLQY) have hindered their widespread adoption. In this study, pyrene is used as the sole precursor to introduce various heteroatom dopants, and followed by solvothermal treatment to synthesize blue-, green-, and red-emissive CQDs with PLQYs approaching 100% (referred to as "unity-CQDs"). The FBs of these CQDs are all approximately 2 million. Pure unity-CQDs directly emit quasi-single-mode blue, green, and red lasers in a simple mirrorless pumping system that covers an area equivalent to 152.6% of the National Television Standards Committee (NTSC) standard color gamut. These lasers exhibit significantly higher Q-factors, higher gain coefficients, superior stabilities, and lower thresholds than those of Rhodamine B. Additionally, unity-CQDs demonstrate single-photon and two-photon excitation bright fluorescent imaging in biological staining. Furthermore, they can be combined with various polymer materials for solid-state vivid fluorescence applications including flexible high-transparent films, textiles, artwares, and high-precise micron-scale 3D printings. The research findings presented herein will contribute significantly toward the development and practical utilization of multicolor CQDs exhibiting ultra-high PLQYs and FBs.