Raman spectra and vibrational analysis of CsPbI3: A fast and reliable technique to identify lead halide perovskite polymorphs

A major issue in the development of Lead halide perovskites is the assessment of the crystal structure of the samples, due to their typically limited time-stability, and the understanding of the role of external factors that can induce a crystal phase transformation (such as humidity, intense light flux, temperature, etc.). In this perspective, it is of utmost importance to have at disposal a fast and reliable experimental tool able to give an immediate indication of the polymorph of the sample with the possibility to integrate in-situ measurements for constant monitoring. In this paper we propose Raman spectroscopy as the ideal technique to solve this problem. The vibrational analysis of CsPbI3 in the alpha-phase and delta-phase and of the Cs4PbI6 secondary phase is reported and all the vibrational modes are assigned by comparing experimental spectra of the phases to Raman modes calculated within the DFT framework. Finally, the mechanism of laser induced phase degradation was studied using in-situ Raman measurements providing new insights on the secondary phase generated during the process. (C) 2020 The Chinese Ceramic Society. Production and hosting by Elsevier B.V.

Automated summary

This paper proposes using Raman spectroscopy as a fast and reliable experimental tool to assess the crystal structure of lead halide perovskite samples, and studying the mechanisms of laser-induced phase degradation through in-situ Raman measurements. The vibrational analysis and comparison of experimental spectra to Raman modes calculated within the DFT framework can help identify the polymorph of the sample and provide new insights on secondary phases generated during the process.