Numerical studies on a type of mechanical stirring in directional solidification method of multicrystalline silicon for photovoltaic applications

With the increase of the dimensions of multicrystalline silicon ingots obtained by directional solidification, it is necessary to propose new methods allowing to tailor the convection within the melt adapted for large scale crucibles. Melt stirring is widely used to influence the melt flow and the shape of the solid–liquid interface in crystal growth processes.Therefore, the objective of this paper is to study by numerical methods the forced convection induced by an idealized stirrer on the melt flow and interface shape in a directional solidification furnace in order to see the potential of such a device.Numerical simulations were carried out for a pilot scale furnace configuration (38×38×40 cm3). The computational domain used for the 3D-simulations consists of silicon melt and crystal. Time-dependent computations were carried out with the software STHAMAS3D.It was obtained that, the stirrer's rotation leads to a strong increase of both the melt convection and the S–L interface deflection.

► We model the forced convection induced by a stirrer on a silicon melt in directional solidification method.
► We examine the influence of stirrer rotation on melt flow and interface shape.
► Even a small stirrer rotation (5 rpm) can improve the level of mixing in the melt.
► S–L interface deflection increases as the stirrer's rotation increase.