Analysis of grain orientation in cold crucible continuous casting of photovoltaic Si.
Résumé
Grain orientation in multi-crystalline photovoltaic silicon is analyzed in the case of a square shaped ingot produced by cold crucible continuous casting (4C). This technique leads to a specific grain structure: horizontal on the wall where nucleation occurs and vertical at the center of the ingot. EBSD analysis along a solidification path shows that successive Sigma 3 twinning is the predominant source of variation in grain orientation. In fact, depending on the location along the solidification path, only 15-35% of grain boundaries are random boundaries without Sigma 3(n) twinning relationship (1 <= n <= 5) and 34-48% are Sigma 3 twins. The grain orientation distribution is similar at the beginning and end of solidification, and the number of low angle grain boundaries is negligible. (C) 2010 Elsevier B.V. All rights reserved