DIELECTRIC STUDIES ON CH3NH3PBX3 (X=CL AND BR) SINGLE-CRYSTALS

Dielectric dispersion measurements have been performed on CH3NH3PbX3 ( MAPbX(3), X = Cl and Br) single crystals at frequencies between 50 Hz and 1 MHz. Significant dielectric dispersion was observed in the cubic and tetragonal II phases for MAPbCl(3) and in the cubic, tetragonal I and tetragonal II phases for MAPbBr(3). The apparent dielectric dispe rsion was attributed to the ionic conductivity in the crystals. The st atic bulk conductivity was expressed by the Arrhenius-type formula sig ma = (A/T) exp(-Delta E/kT). The activation energies for the ionic con duction along [100] axis for each phase are estimated to be 0.13 eV (c ubic phase) for MAPbCl(3) and 0.132 eV (cubic phase) and 1.60 eV (tetr agonal I phase) for MAPbBr(3).