Interpretation of dielectric behavior and polaron hopping in lead-free antimony-based double perovskite

Abstract

Lately, double perovskite materials have become well-known in the commercialization area owing to their potential use in optoelectronic applications. Here, double perovskite Cs₂AgSbCl₆ single crystals (SCs) with cubic crystal structure and Fmm space group were successfully synthesized via the slow cooling technique. This paper investigates the dielectric relaxation and charge transfer mechanism within Cs₂AgSbCl₆ using electrochemical impedance spectroscopy (EIS) in the 273–393 K temperature range under light. The dielectric response in Cs₂AgSbCl₆ has been explained by the space charge polarization and the ionic motion. The ε′(ω) study at different temperatures shows a remarkable frequency transition at which dε′/dT changes from a positive to a negative coefficient. Based on Stevels approach, the density of traps diminishes with the temperature increase, which improved conduction. However, this approach proves the polaronic conduction in Cs₂AgSbCl₆. 0.42 and 0.21 eV are the binding (E_p) and polaron hopping (W_H) energy values, respectively. Contrary to free-charge carrier motion, polaron hopping was proposed as the principal conduction process since the ambient-temperature thermal energy was lower than E_p. Moreover, the analysis of M′′(ω) and −Z′′(ω) as a function of temperature shows the thermally-activated relaxation from the non-Debye to Debye type model in Cs₂AgSbCl₆. This scientific research offers an essential understanding of the dielectric relaxation behavior, which is required for improving dielectric switches. Also, this paper provides a deep insight into the conduction mechanism within double perovskite materials.