Near‐Infrared Transmitting Films With Programable Optical Cutoff Wavelength for Information Storage and Encryption

Abstract The escalating demand for advanced information security drives the development of functional materials for secure storage. Near‐infrared (NIR)‐transmitting films have emerged as promising candidates. To date, most of them are inorganic materials such as chalcogenide glasses, which restrict the application of it in some scenarios. Herein, we reported a series of intermolecular organic charge‐transfer (CT) cocrystals with readily programmable optical cutoff wavelength for fabricating NIR transmitting films with selective NIR transmission bands. By employing different common donor and acceptor molecules, the absorption cutoff wavelength of the synthesized CT cocrystals can be tuned from the NIR‐I to NIR‐II region. Notably, the NIR transmitting films, which exhibit tunable transmission edges ranging from 710 to 830 nm and even to 930 nm with ideal transmittance (T Vis < 2%, T NIR > 80%) were prepared by combining these CT complexes with polymer matrices. Molecular dynamics calculations indicated that donors and acceptors can recognize and self‐assemble within the polymer matrix, enabling the films to retain the optical properties of CT cocrystals. Finally, we successfully realized information encryption by constructing filter arrays using these developed NIR transmitting films with distinct cutoff wavelengths, which enable selective visualization of infrared‐encoded information under tailored NIR illumination. The method presented in this work could provide a dual‐level encryption tool for advanced security applications.