Compression Eliminates Charge Traps by Stabilizing Perovskite Grain Boundary Structures: An Ab Initio Analysis with...

Area of Science:

• Materials Science
• Solid-State Physics
• Computational Chemistry

Background:

• Grain boundaries (GBs) critically influence perovskite optoelectronic properties.
• Strain engineering offers a new approach to tune perovskite solar cell performance.
• Atomistic understanding of GBs is crucial for advancing perovskite technology.

Purpose of the Study:

• To theoretically investigate the impact of axial strain on CsPbBr3 grain boundary properties.
• To elucidate the mechanisms by which strain affects GB structure and electronic behavior.
• To provide insights into resolving experimental discrepancies regarding perovskite GBs.

Main Methods:

• Development of a machine learning force field for CsPbBr3.
• Ab initio calculations to simulate GB models under varying axial strains.
• Nanosecond timescale analysis of GB structural and electronic dynamics.

Main Results:

• Compressive strain significantly reduces structural fluctuations at GBs.
• Elimination of trap states caused by large-scale distortions under compression.
• GB amorphization under compressive strain leads to nonmonotonic electronic structure changes.
• Strain effects on GB electronic properties are complex and nonmonotonic.

Conclusions:

• Axial strain, particularly compression, can effectively passivate detrimental effects at perovskite grain boundaries.
• The study provides a theoretical framework for understanding and controlling GB properties through strain engineering.
• Findings contribute to resolving conflicting experimental observations in perovskite solar cells.