Electrical Conductivity of Halide Perovskites Follows Expectations from Classical Defect Chemistry

Defect chemistry is key to understand electrical properties of many functional materials including halide perovskites. However, expectations from defect chemistry about the dependency of defect densities on the doping regime of halide perovskites have not yet been clearly confirmed experimentally. Here, we measure the electrical conductivity of the model halide perovskite Methylammonium Lead Iodide over a wide range of iodine partial pressures. We find that with iodine partial pressure the electrical conductivity changes with different slopes in a double-logarithmic representation, indicating changes of the perovskite conductivity mechanism. Considering differences in the mobilities of the various defect species, we derive expectations about the dependence of the total conductivity of the perovskite as a function of iodine partial pressure. We find iodine vacancies dominating the conductivity at low iodine partial pressures, whereas at higher partial pressures holes govern the total conductivity. We find the concentration of iodide vacancies to be similar to 10(18) cm(-3), in good agreement with the expected values based on intrinsic ionic disorder. Finally, for the case that the intrinsic ionic disorder concentration is overestimated, we elucidate the possibility to explain the conductivity profile by impurity induced acceptor doping in the perovskite. Thus, our work will allow to develop a more fundamental understanding about the electrical properties of halide perovskites.

Automated summary

This study investigates the electrical properties of halide perovskites by measuring the electrical conductivity of a model material over a range of iodine partial pressures. The results suggest a relationship between electrical conductivity and iodine partial pressure, indicating changes in the perovskite conductivity mechanism. Additionally, the study reveals that iodine vacancies play a dominant role in conductivity at low partial pressures, while holes govern conductivity at higher pressures.