Understanding the polaron behavior in Cs₂CuSbCl₆ halide double perovskite

Area of Science:

• Materials Science
• Solid State Physics
• Photochemistry

Background:

• Lead-free halide double perovskites (A$_{2}$MM'X$_{6}$) are emerging alternatives to lead-based materials for optoelectronic and photovoltaic applications.
• Research has focused on device engineering, with less attention paid to the intrinsic photophysical properties of these materials.

Purpose of the Study:

• To investigate the fundamental photophysical properties and carrier dynamics of lead-free Cs$_{2}$CuSbCl$_{6}$ double halide perovskite.
• To understand the limitations imposed by intrinsic properties on the performance of Cs$_{2}$CuSbCl$_{6}$ in optoelectronic devices.

Main Methods:

• Ultrafast transient absorption spectroscopy to study photoexcitation dynamics.
• Temperature-dependent AC conductivity measurements to analyze charge transport mechanisms.

Main Results:

• Small polaron formation and localization were identified as key factors limiting carrier dynamics under photoexcitation.
• Single polaron hopping was confirmed as the dominant charge conduction mechanism via AC conductivity.
• Distorted lattice under photoexcitation was found to cause self-trapped states (STSs), leading to ultrafast charge carrier trapping.

Conclusions:

• Small polarons and self-trapped states significantly restrict carrier dynamics in Cs$_{2}$CuSbCl$_{6}$ perovskites.
• Understanding these intrinsic limitations is crucial for the development of efficient lead-free perovskite optoelectronic devices.
• Findings may inform the design of other antimony-based semiconductors.