A density functional study of iron segregation at ISFs and Σ5-(001) GBs in mc-Si

OA Al-Ani, JP Goss, NEB Cowern, PR Briddon, M Al-Hadidi, R Al-Hamadany and MJ Rayson
Solid State Phenomena

Removal of the dilaterous effects of iron in silicon is critical for the performance of multicrystalline silicon (mc-Si) solar cells, with internal gettering at extended defects including stacking faults and grain boundaries being one possibility. We present the results of a density function study of the behavoiur of iron at the intrinsic stacking fault and (001)-Σ5 twist grain boundary, which both represent examples of fully bonded systems. Our results show iron is bound more strongly to the grain-boundary than the stacking fault, which we ascribe to a combination of Si-Fe chemistry and strain relaxation. However, we find that the binding energy of a single Fe atom to these extended defects is modest, and less than 0.5 eV.

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