Steric Ligand Engineering and Flow Crystallization Enable Stable Cyan CsPbBr₃ Nanocrystals for Micro-LED Color Conversion

Although cyan-emitting perovskite nanocrystals (NCs) are attractive for emerging micro-light-emitting diode (micro-LED) displays, their practical deployment remains limited by their inadequate colloidal stability, insufficient process reproducibility, and unstable color-conversion performance. Herein, we report a synergistic strategy that integrates steric ligand engineering with continuous flow crystallization control to produce stable cyan-emitting CsPbBr₃ NCs. By screening protonic ligands with distinct acidities and anchoring groups, we identified dodecylbenzenesulfonic acid (DBSA) as an effective ligand that simultaneously regulates crystal growth and passivates surface defects. The further optimization of DBSA loading, Cs: Pb precursor flow rate ratio, and reaction temperature yielded DBSA-CsPbBr₃ NCs with an emission peak at 493 nm and an average photoluminescence quantum yield of 83.6 ± 2.0% across three independent syntheses. Structural and spectroscopic analyses indicate that DBSA predominantly interacts with Pb-related surface sites, suppresses trap-assisted relaxation, and substantially improves ambient and thermal stability. We subsequently integrated the optimized NCs into patterned GaN microstructures and silicone/PMMA composite films, obtaining cyan emission at 497-498 nm, prolonged solid-state lifetime, and a color-conversion efficiency of 33%. Our results establish a structure-process-property-device framework for cyan perovskite NCs and highlight the potential of flow-enabled steric ligand engineering for micro-LED color conversion.