Revealing Local Disorder in a Silver-Bismuth Halide Perovskite upon Compression

Area of Science:

• Materials Science
• Solid-State Physics
• Crystallography

Background:

• Lead halide perovskites (APbX3) face toxicity concerns.
• Cesium silver bismuth bromide (Cs2AgBiBr6) is a promising lead-free alternative.
• Understanding its structural behavior under pressure is crucial for applications.

Purpose of the Study:

• To investigate the local structural dynamics of Cs2AgBiBr6 under high pressure.
• To identify structural deviations from the average cubic phase.
• To explore the implications of local disorder on material properties.

Main Methods:

• High-pressure synchrotron X-ray total scattering.
• Analysis of the X-ray pair distribution function (PDF).
• Molecular dynamics simulations.

Main Results:

• The average crystal structure remains cubic up to 2.1 GPa.
• Local structure analysis reveals monoclinic distortions and off-centering of atoms.
• Local disorder, particularly in Ag-Br and Bi-Br bonds, increases with applied pressure.
• Molecular dynamics simulations corroborate the experimental findings.

Conclusions:

• Cs2AgBiBr6 exhibits significant local structural disorder not apparent in average structure analysis.
• This disorder is pressure-dependent and enhances upon compression.
• Understanding and controlling this local disorder could be key for tuning halide perovskite properties.