Lead-free double perovskite CsMBiCl (M = Ag, Cu): insights into the optical, dielectric, and charge transfer properties.

Recently, double perovskites have shown excellent potential considering the instability and toxicity problems of lead halide perovskites in optoelectronic devices. Here, the double perovskites CsMBiCl (M = Ag, Cu) were successfully synthesized the slow evaporation solution growth technique. The cubic phase of these double perovskite materials was verified through the X-ray diffraction pattern. The investigation of CsCuBiCl and CsAgBiCl utilizing optical analysis showed that their respective indirect band-gap values were 1.31 and 2.92 eV, respectively. These materials, which are double perovskites, were examined using the impedance spectroscopy technique within the 10 to 10 Hz frequency and 300-400 K temperature ranges. Jonncher's power law was utilized to describe AC conductivity. The outcomes of the study on charge transportation in CsMBiCl (where M = Ag, Cu) suggest that the non-overlapping small polaron tunneling mechanism was present in CsCuBiCl, whereas the overlapping large polaron tunneling mechanism was present in CsAgBiCl.