Sustainable Lignocellulose‐Derived Carbon Quantum Dots with Controlled Ba/Zn Doping as High‐Performance Emissive Layers for OLEDs

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.