Unclonable Perovskite Fluorescent Dots with Fingerprint Pattern for Multilevel Anti-counterfeiting.

Anti-counterfeiting techniques based on physical unclonable functions exhibit great potential in security protection of extensive commodities from daily necessities to high-end products. Herein, by mimicking the stochastic crystallization process of snowflakes in nature, we propose a facile strategy to fabricate unclonable super micro fingerprint (SMFP) array by introducing in-situ grown perovskite crystals for multi-level anti-counterfeiting labels. The unclonable features are formed based on the differential transportation of micro-scale perovskite precursor droplet during inkjet printing process, coupling with randomly crystallization and Ostwald ripening of perovskite crystals originating from their ion crystal property. Furthermore, the unclonable patterns can be readily tailored by tuning in-situ crystallization conditions of the perovskite. 3-dimensional height information of the perovskite patterns are introduced into security label and further transformed into structural color, thus significantly enhancing the capacity of anti-counterfeiting labels. The SMFPs are characterized with tunable multi-level anti-counterfeiting properties, including macro-scale patterns, micro-scale unclonable pattern, fluorescent 2-dimensional pattens and colorful 3-dimensional information.