Flexible Photonic Crystals With Ultralong Organic Phosphorescence for Advanced Anti‐Counterfeiting

ABSTRACT The rapid development of flexible electronics has increased the demand for multi‐level anti‐counterfeiting technologies with high information density and security. Integrating the structural color of photonic crystals (PCs) with the chemical color of ultralong organic phosphorescence (UOP) provides a promising route to multi‑level security, but realizing this combination remains largely unexplored. Herein, we fabricate a series of flexible polymer‐based PCs by vertical self‐assembly of monodisperse microspheres embedded with UOP molecules, achieving synergistic integration of structural color, fluorescence, and phosphorescence. These PCs exhibit mechanical flexibility, angle‐dependent structural colors and long phosphorescent lifetime extending to 2.12 s. The photonic bandgaps determined by the microsphere size can be tuned to selectively modulate the UOP emission, enabling dynamic color control of the afterglow. Furthermore, by integrating colors from physical and chemical origins, we have developed a suite of high‐level anti‐counterfeiting systems including anti‐counterfeit inks, anti‐counterfeit labels and dual‐authentication key. This work provides a mechanically compliant, solution‐processable strategy for advanced optical information encryption, highlighting the synergy between structural photonics and persistent luminescence in advanced security applications.