Interpretation of Resistance, Capacitance, Defect Density, and Activation Energy Levels in Single-Crystalline MAPbI3

Hybrid inorganic–organic lead halide perovskites have attracted a significant research interest in the last 10 years due to their broad-area applications in optoelectronic devices such as solar cells, lasers, photodetectors, and light-emitting diodes (LEDs). Fundamental understanding of the charge transportation, defect density, and activation energy is very important for the further progress of this class of semiconductors. Here, we shed light on the interpretation of resistance, capacitance, defect density, and activation energy levels in single-crystalline methylammonium lead iodide (MAPbI3). In particular, the impedance response of the MAPbI3 crystal as a function of applied bias and temperature (under both increasing and decreasing temperature cycles) is studied for the first time. From the detailed bias- and temperature-dependent studies, we found that the low-frequency capacitance values are influenced by ion density and mobility. Consequently, single-crystalline MAPbI3 depicts an activation energy of 0.53–0.54 eV with an exceptionally low electronic trap density of 0.96 × 1010 cm–3. The present study illustrates that the net electrochemical impedance spectra are due to ionic capacitance coupled to a resistance. The associated resistance is related to the conductivity of the perovskite crystal. These findings are helpful to understand the fundamental electrical properties of the MAPbI3 single crystal, which could be useful for the further advancement of perovskite single-crystal-based applications.