The Crystal Structure, Band Gap, and Optoelectronic Performance of Lead‐free Cs ₂ PdBr ₄ Metal Halide Single Crystal and its Thin Film

Abstract Pd‐based halide materials play an important role in organic synthesis, catalysis, and optoelectronic areas. As a typical metal halide, Pb‐based perovskite materials have the potential to become a newcomer in the field of photodetectors due to their excellent optoelectronic properties. However, the toxicity of lead has led to its unfriendliness to the environment. Herein, we synthesized the lead‐free Cs 2 PdBr 4 metal halide single crystal (SC). The crystal structure of needle‐like Cs 2 PdBr 4 SC is resolved and identified to monoclinic crystal system and C2 space group by X‐ray diffraction. The band gap of Cs 2 PdBr 4 SC is extrapolated to 1.54 eV by absorption and reflection spectra. Cs 2 PdBr 4 thin films (TFs) on ITO Interdigitated electrodes (IEs) were prepared by methods of vacuum evaporation. The photodetectors based on Cs 2 PdBr 4 ‐ITO IEs exhibit regular responses under 397–564 nm monochromatic light, stable operation at weak light intensity of 1 mW/cm 2 (397 nm), a responsivity of 0.27 mA/W and a detectivity of 1.13×10 6 Jones. This study can arouse interest in catalysis and photodetector.