CH₃NH₃PbI₃ perovskites: Ferroelasticity revealed

Area of Science:

• Materials Science
• Solid-State Physics
• Renewable Energy

Background:

• Organic-inorganic perovskites exhibit high photovoltaic conversion efficiency, with ferroelectricity proposed as a contributing factor.
• Distinguishing ferroelectricity from coexisting phenomena like piezoelectricity and ferroelasticity is experimentally challenging.
• The role of domain structures in perovskite properties and device stability remains an active area of research.

Purpose of the Study:

• To provide experimental evidence for ferroelectricity or other domain phenomena in methylammonium lead iodide (CH3NH3PbI3).
• To investigate the influence of applied stress on the domain configuration in CH3NH3PbI3.
• To explore the implications of observed domain structures for perovskite solar cell stability and performance.

Main Methods:

• Utilized a combination of microscopic and nanoscale techniques to examine CH3NH3PbI3.
• Investigated both polycrystalline films and single crystals.
• Applied external stress to observe changes in domain structure.

Main Results:

• Provided solid experimental evidence for the existence of ferroelastic domains in CH3NH3PbI3.
• Demonstrated that the configuration of these ferroelastic domains can be controlled by applied stress in both films and crystals.
• Observed no evidence of concomitant ferroelectricity in the studied CH3NH3PbI3 samples.

Conclusions:

• Ferroelasticity is present in CH3NH3PbI3 and its domains are stress-responsive, suggesting potential for strain engineering.
• Ferroelastic domain boundaries may differ from grain boundaries, offering a new factor for enhancing device stability.
• The findings necessitate a re-evaluation of the mechanisms underlying perovskite performance and stability, moving beyond solely ferroelectric explanations.