Phase Selection of Cesium Lead Triiodides through Surface Ligand Engineering

Area of Science:

• Materials Science
• Solid-State Chemistry
• Optoelectronics

Background:

• Cesium lead triiodide (CsPbI3) perovskites show promise for light absorption and red emission.
• Commercialization is hindered by CsPbI3's tendency to form a stable, non-perovskite phase at room temperature.
• Phase engineering is crucial for achieving stable, three-dimensional (3-D) perovskite structures.

Purpose of the Study:

• To identify optimal surface ligands for stabilizing 3-D CsPbI3 perovskites.
• To elucidate the mechanism by which surface ligands stabilize the perovskite phase.
• To understand the interplay between surface and volume free energies in phase competition.

Main Methods:

• Density functional theory (DFT) calculations.
• Thermodynamic evaluations.
• Comparative analysis of ammonium, alcohol, and thiol surface groups.

Main Results:

• Surface ligands can stabilize the desired 3-D CsPbI3 perovskite phase.
• Ammonium groups provide the most significant enhancement in phase stability compared to alcohol and thiol groups.
• Ammonium-passivated CsPbI3 exhibits improved resistance to defect formation and water adsorption.

Conclusions:

• Surface ligand engineering is a viable strategy for stabilizing CsPbI3 perovskites.
• Ammonium-based ligands are highly effective for promoting and maintaining the stable 3-D perovskite structure.
• This stabilization is key for the development of robust CsPbI3-based optoelectronic devices.