Defect calculations using a combined SCAN and hybrid functional in γ-CsPbI₃

Area of Science:

• Materials Science
• Computational Physics
• Renewable Energy

Background:

• Gamma-cesium lead iodide (γ-CsPbI₃) solar cells show high efficiency but their defect properties are poorly understood.
• Computational limitations with hybrid functionals hinder defect analysis.

Purpose of the Study:

• To develop an efficient computational approach for accurate defect property calculations in γ-CsPbI₃.
• To identify and characterize dominant defect types influencing carrier transport.

Main Methods:

• Utilized a combination of SCAN Meta-GGA for structural relaxation and HSE hybrid functional for accurate defect calculations.
• Developed an algorithm to improve computational convergence speed for defect studies.
• Compared results with previous GGA-based calculations.

Main Results:

• The SCAN-HSE method provides qualitatively reliable defect calculations, outperforming GGA-based approaches.
• Identified p-type V_Cs and V_Pb, and n-type Cs_I defects suppress bipolar conductivity.
• Discovered stable bipolar defects I_int and Cs_Pb act as detrimental carrier traps due to strong bond orbital coupling and structural deformation.

Conclusions:

• The new computational strategy enables reliable defect analysis in γ-CsPbI₃.
• Understanding these specific defects is key to overcoming limitations in γ-CsPbI₃ solar cell performance.
• Stronger bond orbital coupling in γ-CsPbI₃ leads to more defect charge states compared to organic perovskites.