Disentangling the effects of structure and lone-pair electrons in the lattice dynamics of halide perovskites.
basic_science · Level V
Where this comes from
- Record sourced from PubMed, PMID 38760360.
- Also identified by DOI 10.1038/s41467-024-48581-x and PMC identifier 11101661.
- Licence recorded as CC BY.
- The licence permits redistribution, so the abstract is shown in full and the full text is available from the publisher.
Abstract
Halide perovskites show great optoelectronic performance, but their favorable properties are paired with unusually strong anharmonicity. It was proposed that this combination derives from the ns<sup>2</sup> electron configuration of octahedral cations and associated pseudo-Jahn-Teller effect. We show that such cations are not a prerequisite for the strong anharmonicity and low-energy lattice dynamics encountered in these materials. We combine X-ray diffraction, infrared and Raman spectroscopies, and molecular dynamics to contrast the lattice dynamics of CsSrBr<sub>3</sub> with those of CsPbBr<sub>3</sub>, two compounds that are structurally similar but with the former lacking ns<sup>2</sup> cations with the propensity to form electron lone pairs. We exploit low-frequency diffusive Raman scattering, nominally symmetry-forbidden in the cubic phase, as a fingerprint of anharmonicity and reveal that low-frequency tilting occurs irrespective of octahedral cation electron configuration. This highlights the role of structure in perovskite lattice dynamics, providing design rules for the emerging class of soft perovskite semiconductors.