Synthesis of MAPbBr3‐Polymer Composite Films by Photolysis of DMF: Toward Transparent and Flexible Optical Physical Unclonable Functions (PUFs) with Hierarchical Multilevel Complexity

Abstract Physical entities with inherent randomness have been investigated as anti‐counterfeiting labels based on physical unclonable functions (PUFs). Herein, a transparent and flexible optical PUF label associated with multilevel complexity is demonstrated by taking advantage of the optical properties of hierarchical morphologies of the composite film composed of metal halide perovskite nanoparticles (MAPbBr 3 NPs) and the intrinsic spinodal‐decomposition‐like phase separation of polymer blend (PMMA/PS blend). Due to the combinatorial effects of the photolysis synthesis of MAPbBr 3 and the thermodynamic instability of the PMMA/PS blend, randomized patterns emerge at two‐level scales. These patterns are intrinsically non‐deterministic, and therefore, the PUF labels from the multilevel random patterns are challenging to replicate. This is mainly attributed to random spot patterns (higher‐level patterns) confined within intricate bicontinuous patterns (lower‐level patterns).