Exploring the Polaron Landscape in Germanium Halide Perovskites: CsGeCl₃, CsGeBr₃, and CsGeI₃

Area of Science:

• Materials Science
• Solid-State Physics
• Computational Chemistry

Background:

• Cesium germanium trihalide (CsGeX3) perovskites possess unique electronic properties.
• These materials are promising for nonlinear optical (NLO) applications.
• Understanding charge localization phenomena is crucial for their physical and electronic behavior.

Purpose of the Study:

• To theoretically investigate electron and hole polaron formation.
• To study self-trapped exciton binding energies.
• To understand charge localization in CsGeX3 perovskites for NLO applications.

Main Methods:

• Hybrid density functional theory (DFT) calculations.
• Analysis of polaron formation energies.
• Investigation of self-trapped exciton configurations.

Main Results:

• Polaron stability decreases in the order CsGeCl3 > CsGeBr3 > CsGeI3.
• Single-electron polarons are highly favorable in CsGeCl3 and CsGeBr3.
• Single-hole polarons are only favorable in CsGeCl3; double electron polarons are favorable across the series.
• Stable self-trapped excitons are found in CsGeCl3 and CsGeBr3.

Conclusions:

• Theoretical insights into polaron formation and self-trapped excitons in CsGeX3 perovskites.
• Findings provide a basis for understanding charge localization effects on electronic properties.
• Opens avenues for optimizing CsGeX3 materials for nonlinear optical applications.