Synthesis, Crystal Structure, and Optical Gap of Two-Dimensional Halide Solid Solutions CsPb₂(Cl_{1- x}Br _x)₅

Area of Science:

• Solid-state chemistry
• Materials science
• Crystallography

Background:

• Perovskite-related materials are vital for developing advanced functional materials.
• Understanding composition-dependent properties is key to material innovation.

Purpose of the Study:

• To synthesize new tetragonal CsPb₂(Cl₁₋ₓBrₓ)₅ solid solutions.
• To investigate the tunability of their structural and optical properties through anion substitution.

Main Methods:

• Hydrothermal synthesis of CsPb₂Cl₅.
• Anion-exchange reactions to form CsPb₂(Cl₁₋ₓBrₓ)₅ solid solutions.
• Rietveld analysis for crystal structure determination.
• UV-vis spectroscopy for optical band gap measurement.
• First-principles calculations (full-potential method, GGA) for band structure analysis.

Main Results:

• Successful synthesis of tetragonal CsPb₂(Cl₁₋ₓBrₓ)₅ (space group I4/mcm) solid solutions.
• Crystal structure parameters were determined and found similar to CsPb₂Cl₅.
• Optical band gap was successfully tuned from 4.5 eV to 3.8 eV via Br⁻ substitution for Cl⁻.

Conclusions:

• CsPb₂(Cl₁₋ₓBrₓ)₅ solid solutions offer a pathway for tuning optoelectronic properties.
• Anion substitution is an effective strategy for band gap engineering in these materials.
• The synthesized materials hold potential for advanced functional material applications.