Discovery of unusual two-dimensional atomic fluctuations in photovoltaic halide perovskite materials

November 4, 2021

Our group, in collaboration with Argonne National Lab, Oak Ridge National Lab and Northwestern University recently reported the discovery of unusual two-dimensional atomic fluctuations in CsPbBr3 in Nature Materials: 

Congratulations to Tyson and Xing for the very nice work!

The all-inorganic halide perovskite compound CsPbBr3 is currently attracting intense interest for radiation applications as well as photovoltaic energy conversion, and is the parent structure from which many hybrid organic-inorganic perovskite photovoltaics are derived. While it is a nominally three-dimensional crystalline structure, our results revealed very peculiar large-amplitude dynamic fluctuations of the atoms in the lattice, which give it a two-dimensional character at the nanoscale (arising from pervasive overdamped anharmonic phonons for PbBr6 octahedral tilts). These fluctuations directly impact the electron-phonon coupling underlying photocarrier thermalization, as well as the phonon-phonon interactions responsible for glass-like thermal transport. The study combined inelastic neutron scattering measurements at the Spallation Neutron Source, and diffuse x-ray scattering measurements at the Advanced Photon Source, together with large-scale atomistic modeling based on ab-initio molecular dynamics on NERSC supercomputers.

 Jill Hemman/ORNL.

(Above) Artist rendition of the way PbBr6 octahedra dynamically tilt around hinge-like bromine atoms (red) in CsPbBr3. Image credits: Jill Hemman/ORNL.


Write up by Ken Kingery:

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