Halogen vacancy migration at surfaces of CsPbBr3perovskites: Insights from density functional theory

R. I. Biega, L. Leppert*

*Corresponding author for this work

Research output: Contribution to journalArticleAcademicpeer-review

Abstract

Migration of halogen vacancies is one of the primary sources of phase segregation and material degradation in lead-halide perovskites. Here we use first principles density functional theory to compare migration energy barriers and paths of bromine vacancies in the bulk and at a (001) surface of cubic CsPbBr3. Our calculations indicate that surfaces might facilitate bromine vacancy migration in these perovskites, due to their soft structure that allows for bond lengths variations larger than in the bulk. We calculate the migration energy for axial-to-axial bromine vacancy migration at the surface to be only half of the value in the bulk. Furthermore, we study the effect of modifying the surface with four different alkali halide monolayers, finding an increase of the migration barrier to almost the bulk value for the NaCl-passivated system. Migration energies are found to be correlated to the lattice mismatch between the CsPbBr3 surface and the alkali halide monolayer. Our calculations suggest that surfaces might play a significant role in mediating vacancy migration in halide perovskites, a result with relevance for perovskite nanocrystals with large surface-to-volume ratios. Moreover, we propose viable ways for suppressing this undesirable process through passivation with alkali halide salts.

Original languageEnglish
Article number034017
JournalJournal of Physics: Energy
Volume3
Issue number3
DOIs
Publication statusPublished - Jul 2021

Keywords

  • Defects
  • Density functional theory
  • First principles
  • Halide perovskites
  • Ion migration
  • UT-Gold-D

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