Formation of homogeneous pyridinic emission states in carbon dots via solid-state carbonization of aminoquinoline: Optical design principles and light-emitting diode applications

Developing carbon dots (CDs) for practical applications faces significant hurdles due to non-homogeneity in their chemical structure, leading to broad spectral distribution and the excitation-energy-dependent behavior of their fluorescence (FL) emission properties. To address this challenge, we implemented solid-state carbonization of 6-aminoquinoline (6-AQ) devoid of any additives that could induce chemical non-homogeneity. This process yielded pyridinic-nitrogen-doped CDs (PN-CDs) characterized by homogenous, uniform emission states arising from pyridine-incorporated heteroatomic structures. Notably, these PN-CDs exhibited excitation-energy-independent FL at 520 nm with a full-width-half-maximum of 70 nm. To elucidate the structure-property relationship in PN-CDs, a comprehensive analysis encompassing time-resolved spectroscopy and ab initio calculations was conducted. Furthermore, we performed a comparative study by manipulating synthesis parameters and utilizing six AQ isomers, offering valuable insights to optimize the optical properties of PN-CDs. Finally, we successfully demonstrated high-color-purity and efficient green light-emitting diodes utilizing PN-CDs, highlighting their potential for future display applications. This paves the way for advancement in optical materials with enhanced performance and reduced environmental impact.