Temperature-dependent charge transport and dielectric relaxation in two-dimensional RbPb2Br5 layered-halide

Abstract

We have reported fundamental aspects on the vacancy-mediated conduction and relaxation mechanisms of charge carriers in 2D RbPb2Br5 layered-halides synthesized via the wet chemical method. The structural deformation and phase transition are not observed in RbPb2Br5 layered-halides from temperature dependence of the x-ray diffraction and differential scanning calorimetry results, respectively. The electronic band structure and total density of states are theoretically calculated and the obtained bandgap from the calculation is around ∼2.89 eV. The impedance results provide the grain and grain boundary contributions to the effective impedance in details. The temperature dependence of the DC conductivity (σDC) and the hopping frequency (ωH) in the different temperature regions is explained by the predominance of the vacancy-mediated charge carrier conduction and relaxation due to the trap states formed by various defects in the layered-halide. The calculated activation energy for the DC conductivity in the low-temperature region (Eσ,LTR ∼ 0.075 eV) is comparatively lower than those obtained in the mid-temperature (Eσ, MTR ∼ 0.58 eV) and high-temperature regions (Eσ, HTR ∼ 1.06 eV). The high value of the activation energy at high temperatures is observed due to the onset of vacancy-mediated charge carrier conduction, leading to high DC conductivity. Furthermore, the value of the activation energy obtained from DC conductivity is much closer to those obtained for the hopping frequency and the dielectric relaxation time in different temperature regions.