Defect tolerance of lead-halide perovskite (100) surface relative to bulk: band bending, surface states, and characteristics of vacancies
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arXiv
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| Natura: | Preprint |
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2023
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| _version_ | 1866916221793861632 |
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| author | Rubel, Oleg Rocquefelte, Xavier |
| author_facet | Rubel, Oleg Rocquefelte, Xavier |
| contents | We characterized the formation of vacancies at a surface slab model and contrasted the results with the bulk of lead-halide perovskites using cubic and tetragonal CsPbI$_3$ as representative structures. The defect-free CsI-terminated (100) surface does not trap charge carriers. In the presence of defects (vacancies), the surface is expected to exhibit $p$-type behavior. The formation energy of cesium vacancies $V_\text{Cs}^{-}$ is lower at the surface than in the bulk, while iodine vacancies $V_\text{I}^{+}$ have a similar energy (around 0.25$-$0.4 eV) within the range of chemical potentials compatible with solution processing synthesis conditions. Lead-iodine divacancies ($V_\text{PbI}^{-}$) are expected to dominate over lead-only vacancies at the surfaces. Major surface vacancies create shallow host-like energy states with a small Franck-Condon shift, making them electronically harmless (same as in bulk). The spin-orbit coupling contributes to the defect tolerance of lead-halide perovskite surfaces by causing delocalization of electronic states associated with $n$-type defects and retraction of lowest unoccupied states from the surface due to a mixing of Pb-$p_{x,y,z}$ orbitals. These results explain a high optoelectronic performance of two-dimensional structures, nanoparticles, and polycrystalline thin films of lead-halide perovskites despite the abundance of interfaces in these materials. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2309_04870 |
| institution | arXiv |
| publishDate | 2023 |
| record_format | arxiv |
| spellingShingle | Defect tolerance of lead-halide perovskite (100) surface relative to bulk: band bending, surface states, and characteristics of vacancies Rubel, Oleg Rocquefelte, Xavier Materials Science We characterized the formation of vacancies at a surface slab model and contrasted the results with the bulk of lead-halide perovskites using cubic and tetragonal CsPbI$_3$ as representative structures. The defect-free CsI-terminated (100) surface does not trap charge carriers. In the presence of defects (vacancies), the surface is expected to exhibit $p$-type behavior. The formation energy of cesium vacancies $V_\text{Cs}^{-}$ is lower at the surface than in the bulk, while iodine vacancies $V_\text{I}^{+}$ have a similar energy (around 0.25$-$0.4 eV) within the range of chemical potentials compatible with solution processing synthesis conditions. Lead-iodine divacancies ($V_\text{PbI}^{-}$) are expected to dominate over lead-only vacancies at the surfaces. Major surface vacancies create shallow host-like energy states with a small Franck-Condon shift, making them electronically harmless (same as in bulk). The spin-orbit coupling contributes to the defect tolerance of lead-halide perovskite surfaces by causing delocalization of electronic states associated with $n$-type defects and retraction of lowest unoccupied states from the surface due to a mixing of Pb-$p_{x,y,z}$ orbitals. These results explain a high optoelectronic performance of two-dimensional structures, nanoparticles, and polycrystalline thin films of lead-halide perovskites despite the abundance of interfaces in these materials. |
| title | Defect tolerance of lead-halide perovskite (100) surface relative to bulk: band bending, surface states, and characteristics of vacancies |
| topic | Materials Science |
| url | https://arxiv.org/abs/2309.04870 |