Analysis of 3D unsteady melt flow and crystallization front geometry during a casting process for silicon solar cells

Abstract

The paper clarifies characteristics of melt convection during a casting process for silicon solar cells (CSi) and the flow effect on crystallization front geometry. 3D unsteady features of the flow in CSi are found to be due to moderate temperature gradients along the melt-free surface and in the melt, which appeared to be sufficient to generate velocity fluctuations of about 1 cm/s in the large melt volume. It has been found that the flow in squared moulds can be essentially asymmetric, which affects the crystallization front geometry. We present a comparison of calculations of the crystallization front shape using different approaches: with 2D approach neglecting the melt flow, with 2D flow analysis, and with 3D unsteady flow analysis.