ABSTRACT Organic light‐emitting diodes (OLEDs) offer lightweight, flexible, and high‐performance displays but face challenges such as high production cost and limited operational stability. Here, we present a sustainable one‐step solid‐state synthesis of nitrogen‐doped carbon quantum dots (CQDs) from lignocellulosic biomass using citric acid and urea. Controlled BaCl 2 and ZnCl 2 doping tunes CQD crystallinity, surface chemistry, and optical properties. Structural analyses (XRD, STEM, XPS) show BaCl 2 promotes graphitized, crystalline CQDs, whereas ZnCl 2 yields amorphous, oxygen‐rich structures. Ba‐doped CQDs exhibit strong blue emission, high quantum yield (60.2%), and superior OLED device performance (256 cd m − 2 ), highlighting the role of metal‐ion‐assisted nucleation in enhancing charge transport and exciton recombination. This study provides a green, scalable route to high‐efficiency CQD‐based OLEDs.
Cengiz et al. (Sun,) studied this question.