Analysis of grain orientation in cold crucible continuous casting of photovoltaic Si

Abstract

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 Σ3 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 Σ3n twinning relationship (1≤n≤5) and 34–48% are Σ3 twins. The grain orientation distribution is similar at the beginning and end of solidification, and the number of low angle grain boundaries is negligible.