Solvent and A-Site Cation Control Preferred Crystallographic Orientation in Bromine-Based Perovskite Thin Films

Area of Science:

• Materials Science
• Solid-State Physics
• Renewable Energy

Background:

• Preferred crystallographic orientation is crucial for charge transport in perovskite and semiconductor films.
• Mechanisms governing halide perovskite orientation remain poorly understood.

Purpose of the Study:

• Investigate factors influencing crystallographic orientation in lead bromide perovskites.
• Elucidate the roles of precursor solvent and organic A-site cations.

Main Methods:

• Experimental investigation of lead bromide perovskite thin films.
• Analysis of solvent effects (dimethylsulfoxide) on crystallization.
• Comparison of methylammonium and formamidinium A-site cations.
• Density functional theory (DFT) calculations of surface energies.

Main Results:

• Dimethylsulfoxide solvent prevents colloidal interactions, promoting preferred orientation.
• Methylammonium cations induce higher preferred orientation than formamidinium.
• DFT reveals lower (100) surface energy for methylammonium perovskites, explaining preferred orientation.
• A-site cations impact ion density and hysteresis but not significantly ion diffusion.

Conclusions:

• Solvent and A-site cation interplay dictates crystallographic orientation in lead bromide perovskites.
• Orientation control is vital for optimizing electronic properties and ionic migration in perovskite solar cells.