Flexible Luminescent Fibers Based on Novel Antimony Halides Toward Advanced Anti‐Counterfeiting and Information Encryption

Abstract Integrating and patterning metal halides into fibers extends their applications toward novel flexible and wearable optoelectronics, where the current relevant studies still focus on the toxic Pb halides. The Sb halides have the intrinsic merits of high stability and environmental friendliness yet remain an inclusive challenge in exploration to progress. Here, based on an idea of the selection of organic cations with large rigid and electron donor characteristics to optimize the lattice distortion and electronic environment of Sb halides, a series of novel Sb halides with different Sb‐X polyhedral configurations (seesaw dimers, square‐pyramidal, and octahedrons) are successfully obtained, achieving a maximal photoluminescence quantum yield (PLQY) of 99.3%. Due to the high solution compatibility of the as‐synthesized Sb halides, they are further assembled into solution‐processable inks, which are later processed into stable luminescent fibers by the electrospinning and facile direct ink writing (DIW) in 3D printing, respectively. The luminescent fibers are successfully used for advanced anti‐counterfeiting and information encryption. This work has developed a predictable design strategy for unknown Sb halides with efficient emissions and extended the Sb halides toward the applications in flexible optoelectronics fields.