Intrinsic Exciton Transport and Recombination in Single-Crystal Lead Bromide Perovskite

Area of Science:

• Materials Science
• Solid State Physics
• Optoelectronics

Background:

• Photogenerated carrier dynamics are crucial for metal halide perovskite device performance.
• Limited sample quality and measurement techniques hinder understanding of intrinsic physics.

Purpose of the Study:

• To directly monitor exciton diffusive transport in high-purity CsPbBr3 single crystals.
• To elucidate the temperature-dependent behavior of carrier mobility and exciton lifetime.

Main Methods:

• Contact-free transient grating spectroscopy was used to measure exciton transport from 26 to 300 K.
• First-principles calculations were employed to model carrier mobility.
• Time-resolved photoluminescence spectroscopy analyzed exciton radiative lifetime.

Main Results:

• Carrier mobility (μ) showed a μ ∼ T⁻³.⁰ scaling below 100 K and μ ∼ T⁻¹.⁷ above.
• First-principles calculations accurately reproduced experimental mobility trends.
• Optical phonon scattering was identified as the dominant mechanism governing mobility shifts.
• Exciton radiative lifetime increased with temperature due to phonon-induced population of dark states.

Conclusions:

• Optical phonon scattering, particularly a single longitudinal optical mode, governs carrier mobility in CsPbBr3 across temperatures.
• Findings resolve discrepancies between theory and experiments.
• Provides critical insights for designing advanced perovskite optoelectronics.