Resolving in-plane and out-of-plane mobility using time resolved microwave conductivity

Abstract

The contactless characterization technique time resolved microwave conductivity (TRMC) provides a means to rapidly and unambiguously approximate carrier mobilities and lifetimes for a variety of semiconducting materials. When using a cavity-based approach however, the technique can conventionally only resolve carrier mobilities in the plane of the substrate. In solar cells, charge carriers are extracted in the direction perpendicular to the substrate, therefore it would be beneficial if one were able to evaluate the mobility in this direction also. Here we present a novel approach for resolving charge carrier mobilities in different planes within a sample. Using a range of 3D-printed sample holders, where the sample is held at various angles relative to the incident light, we are able to simultaneously resolve the mobility in the plane of the sample and out of the plane of the sample. As examples, we have studied the 3-dimensional corner-connected metal halide perovskite methylammonium lead iodide and the 2-dimensional perovskite precusor, lead iodide.