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Article Dans Une Revue Journal of Chemical Physics Année : 2021

The role of Si vacancies in the segregation of O, C, and N at silicon grain boundaries: An ab initio study

Résumé

Grain boundaries (GBs) are defects originating in multi-crystalline silicon during crystal growth for device Si solar cell fabrication. The presence of GBs changes the coordination of Si making advantageous for charge carriers to recombine which brings a significant reduction of carrier lifetimes. Therefore, GBs can be highly detrimental for the device performances. Furthermore, GBs easily form vacancies with deep defect electronic states and are also preferential segregation sites for various impurity species as C, N and O. We studied from first-principles the correlation between structural, energetics and electronic properties of the Σ3{111} Si GB, with and without vacancies, and the segregation of C, N and O atoms. C and O atoms strongly increase their ability to segregate when vacancies are present. However, the electronic properties of the Σ3{111} Si GB are not affected by the presence of O while they can strongly change in the case of C. For N atoms it is not possible to find a clear trend in the energetics and electronic properties both with and without vacancies in the GB. In fact, as N is not isovalent with Si, as C and O, it is more flexible in finding new chemical arrangements in the GB structure. This implies a stronger difficulty in controlling the properties of the material in the presence of N impurity atoms compared to C and O impurities.
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Dates et versions

hal-04022418 , version 1 (09-03-2023)

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Rita Maji, Julia Contreras-García, Nathalie Capron, Elena Degoli, Eleonora Luppi. The role of Si vacancies in the segregation of O, C, and N at silicon grain boundaries: An ab initio study. Journal of Chemical Physics, 2021, 155 (17), pp.174704. ⟨10.1063/5.0067252⟩. ⟨hal-04022418⟩
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