Floating Cast Method as a New Growth Method of Silicon Bulk Multicrystals for Solar Cells

We propose a new growth method named as floating cast method to realize high-quality Si bulk multicrystals for solar cells. The fundamental concept of floating cast method is to perform crystal growth from the top center of Si melt in a crucible without contacting the inner wall until the melt is entirely solidified. By using a small scale furnace, crystals were grown under the concept of floating cast method and by the conventional casting method. As a result, resistivity in the crystal grown by floating cast method was found to be higher, which implies less contamination from the coating material at the crucible wall. In addition, fewer defects such as grain boundaries and dislocations were observed. The conversion efficiency of solar cells based on the crystals grown by floating cast method was revealed to be higher than that by the conventional casting method. Therefore, floating cast method, we propose in this paper, is much promising, which could potentially solve problems in the conventional casting methods and realize high-quality Si bulk multicrystals with fewer impurities and defects.