Yield improvement of polysilicon ingot for solar cell production
LI, TUNG HSUAN
The silicon (Si) solar cell still has highest market share nowadays. To achieve the goal of grid parity, at present the solar wafer manufacturers are facing challenges to enhance quality, to reduce production costs and to increase output and work. The purpose of this study is to prevent reactive between the polysilicon ingot and the silica crucible. This phenomenon will cause chipping or breakage of ingot during the removal of the quartz crucible. Even if the ingot is intact, attached the quartz will result in a damaged lattice structure area, which is likely to cause cracks in brick in the subsequent ingot manufacturing process. This will affect the amount of output and loss on capacity. The work to increase output was carried out in three experiments: 1.On the quartz crucible wall, spray coating with different thickness of silicon nitride, and identify to the most appropriate coating thickness. Experimental results showed that when silicon nitride coating thickness was about 0.08mm, the ingot appearance was most complete and the product yield is highest. 2.Based on the results of Experiment 1, using the same conditions, first brush applied layer of silicon colloidal on the quartz crucible, then added silicon colloidal in the silicon nitride and coating on the inner wall of the quartz crucible with the same thickness of about 0.08mm to verify the ingot yield. The results showed that the appearance of Experiment 2 ingot was far better then Experiment 1. The ingot was the guest coherence problem was not detached , product yield went up to 98%. So we showed that by adding silicon colloidal, ingot yield was improved. 3.We also study the different melting rate with the ingot yield. Experimental results show that with power setting during Melting between 2100kw ~ 2500kw, no different was observed, so the temperature control to improve yields had no significant impact.