Different photocurrent response of Cs₄PbBr₆ particles

Area of Science:

• Materials Science
• Solid-State Physics
• Photophysics

Background:

• Zero-dimensional (0D) all-inorganic cesium lead halide perovskites, especially Cs4PbBr6, are noted for their optical properties and stability.
• The origin of green emission in Cs4PbBr6, despite its ultraviolet B (UVB) bandgap, remains a subject of debate.
• Photocurrent response is a valuable technique for understanding photo-excited carrier dynamics in materials.

Purpose of the Study:

• To investigate the origin of green emission in Cs4PbBr6 by analyzing photocurrent responses.
• To differentiate between Cs4PbBr6 samples with and without visible green emission.
• To correlate material properties with observed optical phenomena.

Main Methods:

• Synthesis of Cs4PbBr6 particles exhibiting no visible emission and those with green emission.
• Measurement and analysis of photocurrent responses for both types of Cs4PbBr6 samples.
• Theoretical calculations to explore lattice defects and exciton behavior.

Main Results:

• Cs4PbBr6 without visible emission displayed a positive photocurrent response.
• Cs4PbBr6 with green emission exhibited a negative photocurrent response.
• Calculations indicated a higher propensity for bromine vacancies in green-emissive Cs4PbBr6, potentially forming charged excitons.

Conclusions:

• The negative photocurrent response in green-emissive Cs4PbBr6 is attributed to a built-in electric field generated by charged excitons.
• Bromine vacancies in the Cs4PbBr6 lattice are proposed as a mechanism for forming these charged excitons.
• This research offers insights into the controversial origin of green emission in Cs4PbBr6.