Lead halide perovksite photovoltaics have amassed a significant amount of interest in the last ten years due to their high open circuit voltages and low non-radiative recombination rates, which enable current state of the art devices to achieve efficiencies of 25%. However, an in-depth understanding of the perovskite excited state and how such high efficiencies can be achieved is still missing. It has been theorized that pervoskites form polarons following photoexcitation, which may explain the favorable optoelectronic properties of the material. However, direct observation of this polaronic state has remained elusive. By using time-resolved infrared (TRIR) spectroscopy we directly probe the spectroscopic signatures of large polarons in perovskite films. Additionally, by probing the vibrational properties of the organic cation, we are able to measure the structural dynamics of the inorganic lattice in the excited state. Our results show that distortions of the inorganic lattice localize charge carriers, leading to extended excited state lifetimes. Based on this information, modifications to the inorganic lattice, through ion substitution, should result in changes to the excited state properties of the material.<br/>

Investigating polaron dynamics in lead halide perovskites using time-resolved infrared spectroscopy

Macromolecular Chemistry: The Second Century

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ACS Spring 2020 National Meeting & Expo

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.