Exploring Polaronic, Excitonic Structures and Luminescence in Cs₄PbBr₆/CsPbBr₃

Area of Science:

• Materials Science
• Solid-State Physics
• Quantum Chemistry

Background:

• Halide perovskites, particularly Cs4PbBr6 and CsPbBr3, are investigated for their ultrafast luminescence properties.
• Understanding the electronic structure is crucial for optimizing their emissive behavior in nanostructures and thin films.

Purpose of the Study:

• To compare the ground-state electronic structure of Cs4PbBr6 and CsPbBr3 using hybrid density functional calculations.
• To elucidate the mechanisms behind the observed ultraviolet and green emissions in these materials.

Main Methods:

• Hybrid density functional calculations were employed to analyze the electronic band structure.
• Calculations included ionization potential and band alignment estimations.

Main Results:

• CsPbBr3 exhibits dispersive band edges, indicating no self-trapped carriers, consistent with low exciton binding energy and high photocurrent.
• Cs4PbBr6 shows polaronic and excitonic features, suggesting lattice-coupled carriers are responsible for UV emission (~375 nm).
• Quantum confinement in CsPbBr3 nanostructures within Cs4PbBr6 leads to fast, green emission.

Conclusions:

• The distinct electronic structures of Cs4PbBr6 and CsPbBr3 explain their different emissive behaviors.
• Lattice-coupled carriers in Cs4PbBr6 contribute to UV emission, while quantum confinement in CsPbBr3 nanostructures drives green emission.