Ionic Ligand-Enhanced Dual Passivation of Orange CsPb(Br/I)3 Quantum Dots for Multicolor Anti-Counterfeiting

Dual passivation has recently become a research hotspot for obtaining high-performance perovskite quantum dots (PQDs). However, exploring efficient ligands and their enhancement mechanisms while expanding their anti-counterfeiting applications remains challenging. This work reports a new organic–organic dual passivation combination. The double-passivated PQDs emit stable orange light at 592 nm (under 450 nm excitation). The introduction of a strongly ionic organic compound, sodium 2-bromoethylsulfonate (SBES), improves defect passivation efficiency and increases Fermi levels, thereby effectively separating excitons and suppressing non-radiative exciton recombination. This ultimately more than doubles the photoluminescence quantum yield (PLQY) and simultaneously enhances thermal stability and moisture resistance, with PL intensity retaining 32% and 70% of its initial value after 12 h under thermal and humid conditions, respectively. The characterization of phase, microstructure, photoelectron spectroscopy, and PL dynamics strongly supports these findings. Finally, the fabrication of multicolor films and barcodes combining other PQDs and a long-persistent phosphor validates the potential application of the material system in anti-counterfeiting. This work facilitates the exploration of novel passivation ligands and their enhancement mechanisms for a robust surface engineering approach, and also provides a reference for multimodal luminescent anti-counterfeiting applications based on multi-phosphor combinations.