Transforming excitation-dependent green to independent yellow emission in citric acid-derived carbon dots via melamine addition for high-performance warm pc-LEDs

다국어 초록 (Multilingual Abstract)

Designing long-wavelength emissive carbon dots (CDs) with high photoluminescence quantum yield (PL QY) is an inevitable component for lighting applications. However, it is still challenging to develop an efficient CDs with excitation-independent emission in long-wavelength regions. In this work, we developed an excitation-independent yellow emissive CD (y-CDs) with PL emission centered at 568 nm via a facile solvothermal treatment of citric acid and melamine using toluene as solvent. The synthesized, y-CDs contain a high degree of conjugated sp2-carbon domains (fused rings) with different surface groups, which serve as a center for photon absorption. The addition of melamine improves the degree of sp2-conjugated carbon domain and surface groups thereby switching the emission of y-CDs from excitation-dependent to excitation-independent emission with excellent PL QY of 80.2%, UV stability, and large Stoke shift. This work not only developed an efficient yellow emissive CD but also explored the possible mechanism of excitation-independent emission and used it for the development of phosphor-converted LEDs. The LED shows warm yellow light with CIE coordinates of (0.48, 0.49), CCT of 2983 K, excellent color purity of 94%, and high thermal stability. This study promotes the development of cost-effective and eco-friendly optoelectronic devices for smooth lighting applications.