Solvent‐Free Synthesis of Inorganic Rubidium Copper Halides for Efficient Wireless Light Communication and X‐Ray Imaging

Abstract Lead‐free metal halides have recently received sustained attention because of their nontoxicity, low‐cost, as well as excellent stability and optoelectronic properties. However, most of the reported lead‐free metal halides are synthesized via slow solution‐processing at high temperature in toxic solvents, which may impede their commercial applications. Here, a solvent‐free strategy is proposed to synthesize inorganic rubidium copper halides (Rb 2 CuX 3 , X = Cl, Br) at room temperature, which exhibit efficient violet emission dominated by a self‐trapped excitons (STEs) mechanism and attractive stabilities against ultraviolet illumination and heating. Thus, Rb 2 CuX 3 powders are employed as emitters and scintillators applied in wireless light communication and X‐ray imaging technologies. Under orthogonal frequency division multiplexing modulation, emitters demonstrate a broad −3 dB bandwidth of 26.3 MHz and a high received data rate of 205.1 Mbps. Additionally, flexible scintillation films based on as‐prepared powders are fabricated and show outstanding X‐ray scintillation properties, including a high spatial resolution of 18.1 lp mm −1 and a low detection limit of 104 nGy air s −1 , as well as promising imaging performance for irregular objects. These results suggest large‐scale production of nontoxic Rb 2 CuX 3 and their potential commercialization in fields of high‐speed light communication and X‐ray radiography.