Unlocking the Role of Lignin in Designing the Carbon Dot‐Based Afterglow Composites: Co‐Precursor and Co‐Ligand

Abstract Effects of precursor and ligand of carbon dots (CDs)‐based composites on tuning their optical properties have been extensively studied. However, comprehensive research on a precursor that can also work as a ligand is currently lacking, which is important for their further development. In this study, CDs@boron oxide (CDs@B 2 O 3 ) is structurally and optically regulated using naturally sourced sodium lignosulfonate (SL) in two ways. As a co‐precursor, SL enables structural rigidity and luminescent group‐oriented regulation of CDs. When serving as a co‐ligand, SL can help B 2 O 3 effectively encapsulate and confine CDs, benefiting the harvest of triplet excitons to enhance stimulated emission. Meanwhile, yellow‐green fluorescence is observed, along with an impressive aqueous quantum yield ≤35.07%, lifetimes up to 358 ms, and thermally activated delayed fluorescence. After further coating CDs@B 2 O 3 onto an alternating‐current light‐emitting diode, stable and gentle white lighting is easily witnessed at the Commission Internationale de L'Eclairage coordinates at (0.33, 0.34). Overall, this work is anticipated to pave the way for widening the synthetic strategy of carbon dots‐based afterglow composites.