Lead-free double perovskite Cs(2)MBiCl(6) (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 Cs(2)MBiCl(6) (M = Ag, Cu) were successfully synthesized via 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 Cs(2)CuBiCl(6) and Cs(2)AgBiCl(6) 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(−1) to 10(6) 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 Cs(2)MBiCl(6) (where M = Ag, Cu) suggest that the non-overlapping small polaron tunneling mechanism was present in Cs(2)CuBiCl(6), whereas the overlapping large polaron tunneling mechanism was present in Cs(2)AgBiCl(6).