Temperature-Dependent Transport Properties of High-Performance Metal Halide Perovskites

We have recently developed a “temperature-dependent carrier-resolved photo-Hall” technique that enables measurements of various transport properties in temperature ranges from 20K to 340K. In the field of optoelectronics applications, the transport characteristics of minority carriers as well as majority carriers are crucial. However, Hall measurement, which is one of the fundamental characterization methods in the semiconductor field, has a limitation in that only information on the majority carrier can be obtained. We have previously developed a “carrier-resolved photo-Hall” technique that enables the extraction of critical parameters for both majority and minority carriers in electronic materials, such as carrier density, mobility, recombination lifetime, and diffusion length. This technology is enabled by a new photo-Hall equation and a highly sensitive AC Hall system based on parallel dipole line magnets. Furthermore, since the temperature can significantly affect the carrier transport and recombination processes in solar cells, understanding the temperature-dependent behavior of charge carrier transport is important for comprehending solar cell performance and operation. Here we report our recent advancements in the “carrier-resolved photo-Hall” technique that allows photo-Hall measurements in the temperature range of 20-340K. A temperature-dependent photo-Hall analysis was successfully performed on a reference single crystalline p-type silicon and on a metal halide perovskite exhibiting a solar cell efficiency of 25.7%. We investigated important information such as temperature-dependent photoconductivity, mobility scattering mechanisms, and dopant energy levels. In the high-performance perovskite thin film samples, the mobility of electrons and holes increased with temperature up to room temperature and then decreased with the further increase of temperature, indicating impurity scattering and phonon scattering are dominant below and above room temperature, respectively. Also, we investigated the influence of temperature and light intensity on transport characteristics, such as carrier density of photo-generated charges, lifetime, and diffusion length. The lifetime and carrier density of photo-generated charges increased with temperature, and this increase can be advantageous in situations where solar cells heat up during operation. This advance in transport characterization technologies will provide a more detailed understanding of carrier transport properties of electronic materials and contribute to the further development in many applications including solar cells.