A rotating organic cation and a dynamically disordered soft inorganic cage are the hallmark features of organic-inorganic lead-halide perovskites. Understanding the interplay between these two subsystems is a challenging problem, but it is this coupling that is widely conjectured to be responsible for the unique behavior of photocarriers in these materials. In this work, we use the fact that the polarizability of the organic cation strongly depends on the ambient electrostatic environment to put the molecule forward as a sensitive probe of the local crystal fields inside the lattice cell. We measure the average polarizability of the C/N-H bond stretching mode by means of infrared spectroscopy, which allows us to deduce the character of the motion of the cation molecule, find the magnitude of the local crystal field, and place an estimate on the strength of the hydrogen bond between the hydrogen and halide atoms. Our results pave the way for understanding electric fields in lead-halide perovskites using infrared bond spectroscopy.
Bibliographical noteFunding Information:
We thank Bingqing Cheng and Hong-Zhou Ye for valuable discussions; Y.W.’s work at IST Austria was supported through ISTernship summer internship program funded by OeAD-GmbH; D.L. and Z.A. acknowledge support by IST Austria (ISTA); M.L. acknowledges support by the European Research Council (ERC) Starting Grant No. 801770 (ANGULON). A.A.Z. and O.M.B. acknowledge support by KAUST.
© 2023 The Authors. Published by American Chemical Society
ASJC Scopus subject areas
- General Materials Science
- Physical and Theoretical Chemistry