Cation Dynamics in Hybrid Halide Perovskites

TL;DR

This paper reviews how neutron scattering techniques reveal the atomic and molecular dynamics in hybrid halide perovskites, explaining their unique properties and potential for optoelectronic applications.

Contribution

It provides new insights into the atomic dynamics and phonon structures of hybrid halide perovskites using neutron scattering, linking these to their physical properties.

Findings

Neutron scattering elucidates phonon band structure.

QENS reveals molecular reorientation dynamics.

Dynamics influence phase stability and electronic transport.

Abstract

Hybrid halide perovskite semiconductors exhibit complex, dynamical disorder while also harboring properties ideal for optoelectronic applications that include photovoltaics. However, these materials are structurally and compositionally distinct from "traditional" compound semiconductors composed of tetrahedrally-coordinated elements with an average valence electron count of silicon. As discussed here, the additional dynamic degrees of freedom of hybrid halide perovskites underlie many of their potentially transformative physical properties. Neutron scattering and spectroscopy studies of the atomic dynamics of these materials have yielded significant insights to the functional properties. Specifically, inelastic neutron scattering has been used to elucidate the phonon band structure, and quasi-elastic neutron scattering (QENS) has revealed the nature of the uncorrelated dynamics pertaining to molecular reorientations. Understanding the dynamics of these complex semiconductors has elucidated the temperature-dependent phase stability and origins of the defect-tolerant electronic transport from the highly polarizable dielectric response. Furthermore, the dynamic degrees of freedom of the hybrid perovskites provides additional opportunities for application engineering and innovation.