Visualizing Light-Induced Microstrain and Phase Transition in Lead-Free Perovskites Using Time-Resolved X-Ray...

Area of Science:

• Materials Science
• Solid-State Physics
• Optoelectronics

Background:

• Metal halide perovskites are key materials for optoelectronics.
• Understanding the lattice-carrier interaction is crucial for performance.
• Ultrafast laser spectroscopy offers indirect structural insights.

Purpose of the Study:

• To investigate the structural dynamics of Cs3Bi2Br9 nanoparticles using time-resolved X-ray diffraction.
• To explore the coupling between photoexcited charge carriers and lattice distortion.
• To understand the impact of laser fluence on perovskite structure.

Main Methods:

• Time-resolved X-ray diffraction (TRXRD) on Cs3Bi2Br9 nanoparticles.
• Probing structural dynamics across picosecond to microsecond timescales.
• Varying laser fluences to observe phase transitions and recovery.

Main Results:

• Observed photoinduced microstrain (up to 0.15%) and lattice expansion (hundreds of nanoseconds) at mild laser fluence.
• Microstrain saturation and partial phase disordering above 1.4 mJ/cm2.
• Photoinduced structural changes exhibit recovery within nanoseconds.

Conclusions:

• Photoexcitation of charge carriers strongly couples with lattice distortion in lead-free perovskites.
• Transient structural changes fundamentally influence the dielectric environment and charge transport.
• TRXRD provides direct insights into photoinduced structural dynamics relevant to optoelectronic applications.