Temperature-dependent dielectric properties of CsPb₂Br₅: a 2D inorganic halide perovskite

Two dimensional (2D) CsPb₂Br₅have been successfully synthesized via the chemical precipitation method. Detailed structural, morphological, optical, and dielectric studies of these materials have been performed. These 2D CsPb₂Br₅plates (of thickness around 200-300 nm) are ascribed to a tetragonal lattice system withI4/mcmspace group. The dielectric attributes such as dielectric constant, electrical modulus, loss factor, and the DC, and AC conductivities, are observed to be varying appreciably with temperature over an extensive frequency window of 10 Hz-50 MHz. The Nyquist plots are investigated using the Maxwell-Wagner equivalent circuit model, which shows the impact of grains and grain boundaries on the overall impedance. Both the free charge conductivity and space charge increase with an increment in temperature, as revealed from the modified Cole-Cole plot. The relaxation time and relaxation mechanism of 2D CsPb₂Br₅are estimated using the Kohlrausch-Williams-Watts equation. Variation in DC conductivity and relaxation time, as a function of temperature, closely resembles Arrhenius' behavior. Value of activation energy calculated from the DC conductivity corroborates with the same derived from relaxation time. The observation of high dielectric constant and nominal dielectric loss for CsPb₂Br₅perovskite offers enormous potential in energy harvesting and storage devices.