One-Pot Synthesis of Orange Emissive Carbon Quantum Dots for All-Type High Color Rendering Index White Light-Emitting Diodes

The challenges of toxicity and stability of traditional long-wavelength emitting luminescent materials undoubtedly restrain their widespread applications. Some remedial proposals do not fundamentally solve these problems. So, the development of new types of long-wavelength emitting luminescent materials has become a new trend. Herein, orange emissive carbon quantum dots (O-CQDs) are successfully prepared by a simple one-step solvothermal approach using 1-amino-2-naphthol hydrochloride and citric acid (CA). Interestingly, O-CQDs can always be achieved by the regulation of different reaction conditions (e.g., CA concentration, temperature, and reaction times), which is closely related to the fixed structure of O-CQDs inherited from the used precursor. An O-CQD displays its homogeneous size distribution with an average size of 2.5 nm and obtains a high-graphitoid sp2 hybrid architecture. Impressively, O-CQDs exhibit remarkable photoluminescent (PL) properties, including excitation-independent behavior, thermostability, photostability, and the robust non-solvatochromic effect, in different solvents due to their efficient π-conjugated system. These excellent properties lay the optical foundation of O-CQDs for the construction of high-performance white-light-emitting diode (WLED) devices. More importantly, O-CQDs are employed as a light regulator combined with yellow emissive CQDs to form the phosphor, and then CQD phosphor-based all-type WLEDs with a high color rendering index (CRI, ≥81) are realized. This work provides a new avenue for the exploration of low-cost, environment-friendly, and high-performance CQD phosphor-based all-type WLEDs using long-wavelength emitting CQDs as a light regulator.