Scalable synthesis and optical tuning of CsPbBr nanocrystal inks for dual-color anti-counterfeiting applications.

We present a scalable, ambient-air synthesis of CsPbBr perovskite nanocrystal (NC) inks with enhanced optical performance and environmental stability, enabled by post-synthetic surface modification using oleylamine (OAm). Systematic tuning of OAm concentration led to NCs with reduced particle size, improved crystallinity, and effective defect passivation, yielding a peak photoluminescence quantum yield (PLQY) of 93.1% and a prolonged carrier lifetime of 84.02 ns. These modified NCs exhibited significantly improved long-term structural stability compared to unmodified samples. Furthermore, halide exchange iodine incorporation enabled controlled emission tuning from green to red. Dual-color emissive inks were digitally printed into high-resolution patterns on flexible substrates, which remained inconspicuous under visible light but displayed vivid fluorescence under UV illumination. This dual-mode visibility offers a secure and versatile platform for next-generation anti-counterfeiting technologies and information encryption, demonstrating the potential of perovskite NCs in advanced functional ink applications.