Application of multi heaters in a directional solidification furnace for silicon solar cells

A heating system with multi heaters is applied to a directional solidification furnace for solar silicon. Transient global simulations were carried out to study the effects of power distribution on the global heat transfer, the melt convection and the melt-crystal (m-c) interface shape in a solidification process. The simulations included melt convection, argon flow, thermal conduction, thermal radiation and phase change in the furnace. The power distribution ratio between the upper side heater and the lower side heater was adjusted. It was found that the power distribution could significantly influence the global thermal field, the silicon melt flow pattern and the m-c interface shape through the process. If the power distribution between the two side heaters is not appropriate, there would be vacuole or high thermal stress in the Si ingots. The research demonstrates that application of multi heaters is an effective method to control and optimize the thermal field in a directional solidification furnace for multi-crystalline Si ingot of high quality.