Defects of monolayer PbI₂: a computational study

Area of Science:

• Materials Science
• Solid State Physics
• Computational Chemistry

Background:

• Lead iodide (PbI2) is essential for hybrid perovskite optoelectronics.
• The origin and impact of PbI2 defects on its properties remain unclear.
• Experimental observations frequently note multifarious defects in PbI2.

Purpose of the Study:

• To systematically investigate the defects in PbI2 using first-principles calculations.
• To predict likely defect structures and calculate their formation energies.
• To understand the influence of defects on opto-electrical performance.

Main Methods:

• First-principles calculations (Density Functional Theory - DFT).
• Prediction of defect structures in 1T and 1H phases of PbI2.
• Calculation of formation energies for neutral and charged defect states.

Main Results:

• Identified likely defect structures in both 1T and 1H PbI2 phases.
• Calculated formation energies considering neutral and charged states.
• Found low formation energy for neutral iodine vacancies (VI).
• Determined that charged lead vacancies (VPb) are dominant and increase conductivity.
• Observed low formation energy for PbI2, indicating weak Pb-I interaction.

Conclusions:

• Defect behavior in PbI2 is complex, with different vacancies dominating under neutral and charged conditions.
• Charged lead vacancies significantly influence PbI2 conductivity.
• The weak Pb-I interaction in PbI2 contributes to its defect flexibility.
• Findings provide insights for suppressing detrimental defects to enhance opto-electrical performance.