A Dual‐Excitation Light‐Harvesting System Based on a Flexible Silicon Composite Containing Ca 2 Sr(PO 4 ) 2 : Ce 3+ , Sm 3+ , Designed for Multimodal Anti‐Counterfeiting and Secure Information Encryption

ABSTRACT Advanced anti‐counterfeiting technologies require luminescent materials capable of generating dynamic and difficult‐to‐reproduce optical responses. The research focuses on a dual‐excitation light‐harvesting system based on flexible silicone composites containing Ca 2 Sr(PO 4 ) 2 : Ce 3+ , Sm 3+ phosphors, designed for multimodal anti‐counterfeiting protection and secure information encryption The co‐doped phosphate exhibits excitation‐dependent emission resulting from efficient Ce 3+ → Sm 3+ energy transfer and multisite occupation of dopant ions, enabling tunable luminescence under different excitation wavelengths. Temperature‐dependent studies additionally reveal a phonon‐assisted energy transfer process leading to enhancement of Sm 3+ emission. The combination of excitation‐ and temperature‐controlled luminescence enables reversible color switching and generation of complex optical signatures that are difficult to counterfeit. As a proof of concept, the phosphor is incorporated into a flexible silicone security label displaying distinct emission patterns observable using a simple UV source and camera detection. Furthermore, a novel encoding platform is proposed, enabling message encryption through the selection of material composition and controlled excitation conditions. The developed dual‐excitation composite represents a promising strategy for next‐generation flexible anticounterfeiting systems, adaptive optical labels, and secure data encryption technologies.