Lead-free double perovskite Cs2MBiCl6 (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 Cs2MBiCl6 (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 Cs2CuBiCl6 and Cs2AgBiCl6 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 Cs2MBiCl6 (where M = Ag, Cu) suggest that the non-overlapping small polaron tunneling mechanism was present in Cs2CuBiCl6, whereas the overlapping large polaron tunneling mechanism was present in Cs2AgBiCl6.

Automated summary

Recently, double perovskites Cs2MBiCl6 (M = Ag, Cu) were successfully synthesized and their cubic phase was confirmed. The indirect band-gap values of Cs2CuBiCl6 and Cs2AgBiCl6 were determined to be 1.31 and 2.92 eV, respectively. Impedance spectroscopy revealed different charge transportation mechanisms, with Cs2CuBiCl6 exhibiting non-overlapping small polaron tunneling and Cs2AgBiCl6 exhibiting overlapping large polaron tunneling.