Highly detrimental dislocation clusters were frequently observed in lab-scale as well as industrially produced multicrystalline silicon ingots for solar cell applications. An investigation was made here of dislocation clusters and how they developed over the whole height of a pilot-scale ingot. A 12kg ingot, cast in a pilot-scale directional solidification furnace using a standard slip cast silica crucible and standard coating containing silicon nitride powder, was studied with respect to dislocation clusters. Dislocation clusters originating from grain boundaries were identified and followed from an early stage to the top of the ingot. One possible model for growth and multiplication of the dislocations in the clusters during solidification where slip on the {1¯10}<110> system must be allowed was described in detail. Another possible mechanism was also considered.

Growth of Dislocation Clusters during Directional Solidification of Multicrystalline Silicon Ingots. B.Ryningen, G.Stokkan, M.Kivambe, T.Ervik, O.Lohne: Acta Materialia, 2011, 59[20], 7703-10