First-Principles Study of Halide Modulation on Deep-Level Traps in FAPbI₃

Area of Science:

• Materials Science
• Solid State Physics
• Photovoltaics

Background:

• Organic-inorganic hybrid perovskites, particularly FAPbI3, are promising for solar cells.
• High defect densities can significantly reduce the efficiency of these devices.
• Iodine interstitials (Ii) are known to create detrimental deep-level traps.

Purpose of the Study:

• To investigate the influence of bromine (Br) and chlorine (Cl) on iodine defect properties in FAPbI3.
• To understand how these halogen dopants affect defect energy levels and carrier transport.
• To assess the impact on the efficiency of perovskite solar cells.

Main Methods:

• First-principles calculations were employed to model defect properties.
• Analysis focused on the electronic structure and defect formation energies.
• Simulations examined the impact of Br and Cl interstitials on FAPbI3.

Main Results:

• Br and Cl interstitials minimally alter the FAPbI3 band structure.
• These interstitials significantly modify defect energy levels, shifting them closer to the valence band.
• Deep-level traps from iodine interstitials are converted into shallow-level traps by Br and Cl.

Conclusions:

• Co-doping FAPbI3 with Br and Cl effectively suppresses non-radiative recombination.
• This defect engineering mitigates the negative effects of iodide-related defects.
• The strategy enhances carrier transport and preserves light absorption, improving perovskite solar cell performance.