Optimization of heat transfer by adjusting power ratios between top and side heaters for casting high-performance multi-crystalline silicon ingots

• The effects of variable power ratio on the thermal field were investigated.
• The global modeling for directional solidification process was performed.
• A preferable crystal–melt interface and a low thermal stress can be achieved.
• The crystal quality and the conversion efficiency of solar cells were improved.

Numerical simulations were applied to analyze the effects of the power ratios between top and side heaters on the crystal–melt (c‐m) interface and the thermal stress distribution during the solidification process. The simulation results showed that among the different increase velocities of the power ratio, increasing the power ratio uniformly provided a most favorable solidification process: a slightly convex c–m interface shape and low thermal stress were obtained. The optimized design was implemented in casting experiments, which showed that the high-performance multi-crystalline silicon ingot had a vertical columnar structure and a lower dislocation density. The average conversion efficiency of solar cells was about 0.08% higher with this design (18.24%) than with the original design (18.16%).