Yb <sup>3+</sup> ‐Complex‐Mediated Assembly of CsPbBr <sub>3</sub> Nanocrystals Enables Multilevel Optical Encryption
Yao Kou, Zhaoxin Yang, Guoying Tan, Lijuan Liang, Haoran Cheng, Pingru Su, Yu Tang
Abstract
Abstract Counterfeiting presents severe global economic and safety threats, driving demand for advanced anti‐counterfeiting solutions. While CsPbBr 3 perovskite nanocrystals (NCs) offer exceptional optical encoding properties, their application is limited by intrinsic instability and single‐mode emission. This work introduces a tripodal quaternary ammonium‐functionalized Yb 3+ complex ([YbL 3 ] 3+ ) as a “molecular adhesive” to simultaneously address these constraints. The complex directs CsPbBr 3 NC self‐assembly into ordered 3D cubic superstructures (Yb‐CsPbBr 3 SNCs) via ionic interactions while passivating surface defects. Resultant Yb‐CsPbBr 3 SNCs exhibit three critical advances: 1) Dual‐mode luminescence (519 nm NC green emission; 980 nm Yb 3+ NIR emission) enabling covert authentication; 2) Significantly enhanced environmental stability, particularly against water and heat; 3) Intrinsic microscale assembly randomness permitting physically unclonable function (PUFs) generation for high‐security encryption. Exploiting differential NIR emission, thermal stability, and humidity sensitivity between Yb‐CsPbBr 3 SNCs and CsPbBr 3 NC, a multi‐stimuli‐responsive (NIR/thermal/humidity) anti‐counterfeiting platform is demonstrated with flexible “one‐time” or “repeated” decryption. Stochastic assembly further enables high‐capacity PUFs exhibiting validated randomness, uniqueness, and similarity index. This Yb 3+ ‐complex‐mediated assembly strategy overcomes perovskite NC stability and encoding limitations, unlocking dual‐mode luminescence and unclonable security features to establish a versatile platform for next‐generation anti‐counterfeiting and optical encryption.