Modeling on Directional solidification of Silicon for Solar Cell Applications

The Directional Solidification is a very important technique for growing high quality multi-crystalline silicon at large scale for PV solar cells. The physics governing the growth of multi-crystalline silicon in the Directional Solidification System involves complex non-linear transport phenomena including but not limited to heat transfer, solidification, thermal stress development, and the formation of defects. Specifically, heat transfer and solidification process have significant impact on the quality and productivity of the crystals. This paper is aimed to achieve an advanced understanding of the heat transfer and solidification during the growth process and to identify important design and control parameters that can be modified to improve the processing conditions. To achieve this goal, a coupled heat transfer and fluid flow properties were analysed to investigate the heat transfer on the molten silicon in the crucible during solidification process. A 3D numerical approach is successfully used by finite element method. The temperature distribution, the primary and secondary vorticity generation in molten silicon are simulated and analysed for various Rayleigh numbers. The information obtained from this research will help to improve furnace design and process control for producing high quality multi-crystalline silicon ingots at high throughput.