Anomalous Structural Evolution and Glassy Lattice in Mixed-Halide Hybrid Perovskites

Area of Science:

• Materials Science
• Solid-State Physics
• Photovoltaics

Background:

• Hybrid halide perovskites are promising for solar cells due to excellent optoelectronic properties.
• Compositional engineering, like halide mixing, optimizes perovskite performance.
• Hybrid perovskites exhibit temperature-dependent structural phase transitions.

Purpose of the Study:

• Investigate the impact of halide mixing on structural phase transitions in hybrid perovskites.
• Characterize the crystallographic phases and their temperature dependence.
• Understand the relationship between structural evolution and material properties.

Main Methods:

• Synthesis of mixed-halide hybrid perovskite single crystals (MAPbI3-xBrx).
• Utilized a combination of X-ray diffraction and spectroscopic techniques.
• Analyzed structural changes across a range of temperatures.

Main Results:

• Phase transitions are significantly suppressed in mixed-halide perovskite single crystals.
• Multiple crystallographic phases coexist over a broad temperature range.
• A novel, slightly distorted monoclinic phase dominates above 100 K.

Conclusions:

• Mixed halide composition profoundly influences structural phase transitions in hybrid perovskites.
• Anomalous structural behavior is linked to glassy organic cation dynamics and optical phonons.
• This study reveals complex interactions between composition, lattice dynamics, and properties in hybrid perovskites.