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In recent times, double perovskites have demonstrated promising potential as an alternative to address the instability and toxicity challenges associated with lead halide perovskites in optoelectronic applications. In this study, we successfully prepared Cs2MSbBr6 (M = Cu, Ag) double perovskite materials using the slow evaporation solution growth technique. The X-ray diffraction pattern confirmed the presence of the cubic phase in these synthesized materials. Furthermore, the optical analysis of Cs2CuSbBr6 and Cs2AgSbBr6 revealed their respective indirect bandgap energies to be 1.72 and 2.0 eV. The impedance spectroscopy technique was employed to investigate the properties of these materials, specifically double perovskites, across a frequency range of 10−1 to 106 Hz and at temperatures ranging from 303 to 403 K. To describe the AC conductivity, Jonscher's power law was utilized. The findings of the charge transportation study on Cs2MSbBr6 (M = Cu, Ag) indicate the existence of the non-overlapping small polaron tunneling mechanism in Cs2CuSbBr6, while the overlapping large polaron tunneling mechanism is observed in Cs2AgSbBr6. [ABSTRACT FROM AUTHOR]

• FAPbI 3 is successfully synthesized via the inverse temperature crystallization method. • The DSC measurements indicate that FAPbI 3 goes through a phase transformation at T = 300 K from the hexagonal to the cubic system. • Optical analysis of FAPbI 3 shows the direct band-gap value of ∼ 1.4 eV. • The study on charge transportation within FAPbI 3 suggests the presence of the nonoverlapping small polaron tunneling mechanism (hexagonal phase) and the overlapping large polaron tunneling mechanism (cubic phase). Recently, hybrid halide perovskite solar cells have drawn the researchers' attention, owing to their high-power conversion efficiency. Among the different compounds, MAPbI 3 (MA = Methylammonium CH 3 NH 3) and FAPbI 3 (FA = Formamidinium CH(NH 2) 2) are especially potential candidates since their bandgap suited the energy range of visible light. Here, the hybrid perovskite FAPbI 3 is successfully synthesized via the inverse temperature crystallization method. Different characterization techniques such as variable-temperature structural analyses, differential scanning calorimetry (DSC), and impedance spectroscopic analysis show that FAPbI 3 presents a phase transition at T = 300 K from the hexagonal to the cubic symmetry. Optical analysis of FAPbI 3 shows the direct band-gap value of ∼1.4 eV. FAPbI 3 is characterized by impedance spectroscopy technique performed in the 10−1–106 Hz frequency and 210–390 K temperature ranges. The alternating current (AC) conductivity is illustrated in terms of Jonncher's power law. The study on charge transportation within FAPbI 3 suggests the presence of the NSPT (non-overlapping small polaron tunneling) and OLPT (overlapping large polaron tunneling) models in the hexagonal and cubic phases, respectively. [Display omitted] [ABSTRACT FROM AUTHOR]