Efficient and High Color‐Purity Red and Deep‐Red Circularly Polarized Luminescence From Carbon Quantum Dots Enabled by Helical Co‐Assembly Strategy

Abstract Quantum dots (QDs) are emerging as promising emitters for achieving efficient and high color‐purity narrowband circularly polarized luminescence (CPL), which holds great promise for 3D flexible stereoscopic displays. However, the currently reported high color‐purity CPL from QD emitters primarily relies on conventional heavy‐metal Cd/Pb‐based QDs, which suffer from significant toxicity issues and thus severely limit their potential for widespread applications. In this study, the first instance of efficient, high color‐purity narrowband CPL derived from environmentally friendly carbon QDs (CQDs) is presented. By incorporating high color‐purity red and deep‐red CQDs (RCQDs and DRCQDs) with nematic liquid crystals E7 and chiral dopants R/S5011, it has formed CQDs‐chiral liquid crystals (CQDs‐CLCs) composites through a helical co‐assembly approach. These CQDs‐CLCs composites exhibit remarkable optical properties, featuring sharp emission peaks with ultranarrow full width at half maximum values of 22 nm for DRCQDs‐CLCs and 37 nm for RCQDs‐CLCs, coupled with high dissymmetry factor (g _lum ) values reaching 1.26. Furthermore, by modulating the photonic bandgap (PBG), it can effectively control and even reverse the CPL signals, particularly the g _lum value. These innovative CPL materials are successfully implemented in multilevel anticounterfeiting designs and information encryption applications.