Continuous In-Line Synthesis and Surface Passivation of Perovskite Nanocrystals via a Hybrid Multistep Flow Reactor

Perovskite nanocrystals (PeNCs) are promising photoactive materials for next-generation display applications owing to their strong absorption, narrow emission bandwidth, and tunable band gap. However, batch-based hot-injection synthesis is limited by discontinuous operation and difficulties in scale-up, while post-synthetic ligand exchange adds extra processing steps that can destabilize the labile PeNC surface. In this study, we developed a two-zone hybrid continuous-flow reactor (h-CFR) that integrates CsPbBr₃ PeNC synthesis with in-line aromatic ligand exchange. A room-temperature liquid-phase Cs precursor was formulated to enable continuous feeding through stainless steel tubing, and three static mixer geometries were compared to evaluate the effect of precursor mixing on emission bandwidth. The vortex mixer produced CsPbBr₃ PeNCs with a photoluminescence (PL) peak at 519 nm and a full width at half-maximum (FWHM) of 18.4 nm. Subsequent in-line exchange using benzoic acid and 4-phenylbutylamine increased the photoluminescence quantum yield (PLQY) from 69 to 95% while maintaining a narrow FWHM of 18.6 nm. The optimized process was further operated continuously for 3 h, yielding 1.8 L of a PeNC dispersion and 6.12 g of purified powder. These results demonstrate a practical continuous strategy for integrating PeNC formation and surface passivation in a single-flow process.