First-principles comparative study of perfect and defective CsPbX₃ (X = Br, I) crystals

Area of Science:

• Materials Science
• Computational Chemistry
• Solid State Physics

Background:

• Halide perovskites like CsPbI3, CsPbBr3, and CsPbCl3 are crucial for optoelectronic applications.
• Understanding their structural stability and defect properties is key to improving device performance and longevity.
• Computational methods offer a powerful approach to investigate these complex materials at an atomic level.

Purpose of the Study:

• To investigate the atomic and electronic structure of perfect and defective CsPbI3, CsPbBr3, and CsPbCl3 crystals.
• To determine the relative stability of these perovskite compounds.
• To analyze the energetic favorability of different defect configurations, particularly interstitial halide species.

Main Methods:

• First-principles Density Functional Theory (DFT) using the PBESOL0 hybrid functional.
• Calculation of decomposition energies to assess crystal stability.
• Computation of temperature-dependent heat capacity.
• Analysis of interstitial halide defect formation energies.

Main Results:

• A stability trend of CsPbBr3 > CsPbI3 > CsPbCl3 was identified for perfect crystals.
• Calculated heat capacities showed good agreement with experimental data.
• Interstitial halide dimers (X2-) are energetically favored in CsPbI3 but not in CsPbBr3.
• A loose trimer configuration (Br32-) is energetically preferred for interstitial defects in CsPbBr3.

Conclusions:

• The study provides fundamental insights into the stability and defect physics of lead halide perovskites.
• The distinct behavior of interstitial halide defects in CsPbI3 and CsPbBr3 has significant implications for understanding charge carrier recombination and device stability.
• DFT calculations serve as a valuable tool for predicting and explaining the properties of these important materials.