Patternable Stimuli‐Responsive Perovskite Fiber Membranes for Underwater Anti‐Counterfeiting and Information Encryption

ABSTRACT All‐inorganic lead halide perovskites are favored for next‐generation optoelectronic devices due to their exceptional photoluminescence quantum yields (PLQYs), wide color gamut, and structural tunability. However, their application in intelligent materials, especially for dynamic optical encryption and anti‐counterfeiting in aqueous or humid environments, remains challenging owing to their poor water stability and lack of tunable response under external stimuli. Here, we reported a scalable strategy to fabricate large‐area (15 cm × 25 cm), hierarchically porous perovskite fiber membranes (PFMs) that enabled water‐responsive, reversible fluorescence modulation. By developing a dual‐ligand surface passivation approach, combining hydrophilic supramolecular cyclodextrins and hydrophobic long‐chain alkylamines, we simultaneously achieved surface passivation, water resistance, as well as dynamic bandgap modulation and defect engineering within a single material platform. The resulting blue‐emitting PFMs demonstrated a high PLQY of 86.3%, narrow‐band emission (full‐width at half‐maximum value of ~20 nm), enhanced color purity up to 96.4%, and long‐term stability (> 4000 h) under ambient conditions. More interestingly, moisture‐induced ligand reorganization enabled reversible fluorescence shifts from deep‐blue (461.1 nm) to cyan‐green (504.9 nm) across multiple cycles (with > 95% photoluminescence intensity retention) and in a wide pH range (3–13). We further demonstrated an ASCII‐encoded microdots array and dual‐mode optical encryption system that allowed orthogonal decoding via moisture and ultraviolet stimuli, highlighting the potential of these materials for underwater anti‐counterfeiting and dynamic information encryption. This work provides a new paradigm for integrating intelligent stimulus responsiveness with stable optoelectronic performance in perovskites, paving the way for their application in secure information technologies and smart photonic devices in harsh environments.