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

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: https://www.nature.com/articles/s41563-021-00947-y 

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

(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:

https://mems.duke.edu/about/news/twisting-flexible-crystals-key-solar-energy-production

Science highlights:

https://www.eurekalert.org/news-releases/727306

https://cosmosmagazine.com/science/how-perovskites-twist/

https://www.sciencedaily.com/releases/2021/03/210315141758.htm