N‐Butyl Pyridinium Chlorobismuthates (III): A Soft Organic‐Inorganic Hybrid Transparent Solid‐State Ion Conductor

Transparent solid-state ionic conductors are emerging as next-generation materials for various modern optoelectronics and energy applications. In this study, an organic-inorganic hybrid metal halide is introduced, tris-N-butyl pyridinium nonachlorido-dibismuthate(III), (C4py)3[Bi2Cl9]. The material is an optically transparent solid-state ion conductor with high ionic conductivity at room temperature. Single crystal analysis reveals a structure composed of N-butyl pyridinium cations and [Bi2Cl9]3− anions, formed by edge-sharing BiCl6 octahedra. The material is thermally stable up to 300 °C and undergoes a melting transition at 101.6 °C. Notably, it demonstrates unidirectional growth in thin films, boasting over 90% optical transparency in the visible wavelength and overall ionic conductivity of 10−3 mS cm−1 at room temperature. (C4py)3[Bi2Cl9] stands out as one of the first reported low-melting, optically transparent ionic solids, showcasing superior ion conduction and holding promise for applications such as electrochromic devices and energy storage.