Inter-Conversion between Different Compounds of Ternary Cs-Pb-Br System

Area of Science:

• Materials Science
• Solid-State Chemistry
• Inorganic Chemistry

Background:

• Cesium lead bromide (CsPbBr₃) perovskites are promising for optoelectronic applications.
• The practical application of CsPbBr₃ is hindered by its inherent instability.
• Understanding phase conversion mechanisms is crucial for stabilizing perovskite materials.

Purpose of the Study:

• To investigate the reversible conversion pathways between CsPbBr₃, Cs₄PbBr₆, and CsPb₂Br₅.
• To elucidate the thermodynamic principles governing these phase transformations.
• To develop controlled synthesis methods for ternary Cs-Pb-Br materials.

Main Methods:

• Preparation of CsPbBr₃ solids via a simple reaction.
• Investigating conversions by reacting CsPbBr₃ with CsBr or PbBr₂.
• Utilizing water extraction to induce CsBr removal and subsequent phase conversion.
• Employing thermal annealing to reverse CsPb₂Br₅ to CsPbBr₃.
• Thermodynamic analysis of the observed chemical reactions.

Main Results:

• CsPbBr₃ can be converted to Cs₄PbBr₆ or CsPb₂Br₅ by reacting with CsBr or PbBr₂, respectively.
• These conversion reactions are exothermic and spontaneous.
• Cs₄PbBr₆ can be converted back to CsPbBr₃, and further to Cs-deficient CsPb₂Br₅ via water extraction.
• CsPb₂Br₅ can be reversely converted to CsPbBr₃ through thermal annealing at 400 °C.

Conclusions:

• The study clarifies the thermodynamic processes behind the conversions of CsPbBr₃, Cs₄PbBr₆, and CsPb₂Br₅.
• Findings provide a novel method for the controlled synthesis of ternary Cs-Pb-Br materials.
• The research elucidates the mechanism underlying the instability of CsPbBr₃ perovskites.