Interpretation of the giant dielectric constant in the single crystal of the CH3NH3PbBr3 perovskite

Abstract

The dielectric studies of the CH3NH3PbBr3 single crystal were conducted in wide frequency and temperature ranges. The giant dielectric constant (up to 106) which was obtained at low frequencies based on these measurements was considered according to the induced polarization of the electrodes caused by the migration of ions and also the intrinsic polarization included in the hybrid network. Various temperature and frequency evolution regimes were shown and considered for the electrical conductivity (σ′(ω,T),σ″(ω,T)) and the dielectric functions (ε′(ω,T),ε″(ω,T)). In accordance with the Cole-Cole relaxation model and the Debye relaxation theory, pertinent phenomenological approaches were used in order to examine the included dielectric properties as well as the conductivity behavior. Hence, at high temperatures, the migration of the CH3NH3+ ions augments electrode polarization in the low-frequency range. At intermediate frequencies, however, ion hopping results in a modified Cole-Cole relaxation model at high temperatures and in a Debye-type relaxation at low temperatures. This study indicates the correlation between the giant dielectric constant whose activation energy depends on the polar CH3NH3+ ions and the alternating current conductivity enforced by ion migration.