Dielectric Spectroscopy on 2D and 3D Metal Halide Perovskites Using an Interdigitated Electrode Geometry*

Metal halide perovskites are a class of 2D and 3D materials that are currently being studied for use in solar energy and other applications. Permittivity is connected to other important characteristics of these materials such as exciton binding energy, effective mass, and transition dipole moment, but has proven challenging to accurately measure.  Using experimental measurements of the impedance of perovskite layers on interdigitated electrodes, we have been able to develop a model which allows us to deduce the frequency dependence of permittivity in these materials. The results show permittivity values for high frequencies (13 MHz) in the range of 4.1-5.1 for PEA2PbI4 (PEPI) and 12-45 for MAPbI3 (MAPI), with details depending on the specific sample.