Lead‐Free All Inorganic Rubidium Copper Halide Rb₂CuX₃ (X = Cl, Br) for UVC Photodetector with Fast Response

Abstract Recently, lead halide perovskites have shown great potential in the photodetection field. Unfortunately, the existence of toxic lead elements restricts their practical application. Herein, high‐quality 1D lead‐free crystals Rb₂CuX₃ (X = Cl, Br) are successfully synthesized in an acidic medium. Rb₂CuCl₃ and Rb₂CuBr₃ display violet photoluminescence emission peaks at 401 and 388 nm with a high exciton lifetime of 12.78 and 59.67 µs, respectively, which is due to self‐trapped excitons (STE). Furthermore, a photodetector is fabricated to detect harmful UVC radiation with Rb₂CuBr₃ as a light absorber. The proposed photodetector has a responsivity of 0.92 mA W⁻¹ and a specific detectivity of 1.57 × 10⁹ Jones with a fast response speed of 2.67/2.70 µs for rise/fall time, respectively. In addition, both the samples show good stability against open air, and continuous ultraviolet light (254 nm), as well as good thermal stability which is necessary for device fabrication. Thus, the present study suggests that stable, non‐toxic, and environment‐friendly Rb₂CuX₃ (X = Cl, Br) can be a promising candidate for future UVC optoelectronic devices.