Thermal Contributions to the Local and Long-Range Structural Disorder in CH3NH3PbBr3
July 21, 2023
We investigated the temperature dependence of the lead (Pb)-bromine (Br) bond distribution, effective spring constant, and dynamic correlations with a combined extended X-ray-absorption fine structure (EXAFS), single-crystal x-ray diffraction (SXRD) and ab initio molecular dynamics (AIMD) study. EXAFS provides a snapshot of the local environment around the probe atom (here Pb and Br), rather than the time- and space-averaged structure obtained from SXRD.
Scientific Achievement
We showed that local structural disorder in a prototypical halide perovskite is driven by thermally activated anharmonic dynamics rather than static disorder.
Significance and Impact
We quantitatively described local structure that results in the optoelectronic properties of halide perovskites and shed light on ion transport mechanisms.
Research Details
- Compared X-ray absorption spectroscopy, SXRD, and ab initio molecular dynamics (MD) bond distances and disorder parameters in CH3NH3PbBr3 from 10K–300K
- Analyzed EXAFS with cumulant expansion to extract local bonding and thermally active disorder
- Observed change in effective Pb-Br spring constant at phase transition related to change in Pb electronic structure
- Compared EXAFS, MD, and XRD bond lengths to show largely correlated Pb-Br motion
