成果報告書詳細
管理番号20140000000689
タイトル*平成25年度中間年報 太陽エネルギー技術研究開発 太陽光発電システム次世代高性能技術の開発 極限シリコン結晶太陽電池の研究開発 (浮遊キャスト成長法による高品質Si 多結晶インゴット結晶成長技術)
公開日2015/1/31
報告書年度2013 - 2013
委託先名国立大学法人名古屋大学
プロジェクト番号P07015
部署名新エネルギー部
和文要約
英文要約Title:High Performance PV Generation System for the Future. R and D on Ultimate Wafer-based Si Solar Cells. (Growth technology of high-quality Si multicrystal ingots using the Floating Cast Method) (FY2010-FY2014) FY2013 Annual Report

We attempted to grow high-quality multicrystalline Si (mc-Si) ingot using the floating cast method. The concept of the floating cast method is to control the crystal growth and microstructures by initial formation of dendrite crystals at the top of the Si melt followed by solidification with minimizing the contact of the ingot with the inner wall of the crucible. We have already succeeded in scaling up the floating cast method to grow a large scale mc-Si ingot for practical size wafers. However, incorporation of impurities from ambient during growth was an issue. To solve the problem, we utilized a crucible cover to control the flow of inert gas. Using the crucible cover, the impurity contamination such as carbon was successfully reduced by the two orders of magnitude. In addition, we investigated the impact of the contact angle of adjacent dendrites crystals on generation of dislocations in mc-Si ingot. As a result, the contact angles of adjacent dendrite crystals and their arrangements were found to affect the density of generated dislocations. We revealed that parallel arrangement of the dendrite crystals is preferable to reduce dislocation density. To realize parallel appearance of adjacent dendrite crystals, we simulated temperature distribution in the furnace so that in-plane temperature gradient appears around the surface of the melt while symmetric temperature distribution could be established inside the melt. We have shown that such a temperature distribution is feasible by appropriate choice and arrangement of the inner parts of the furnace. Furthermore, we demonstrated the enhancements of phosphorus gettering efficiency to remove impurities in mc-Si using multiple cycles of annealing and cooling technique at low temperature. Optimal low temperature annealing was pursued to suppress the defects formation during annealing. The proposed annealing technique gives a significantly greater enhancement of gettering of impurities than continuous annealing, particularly in regions of low defect density. The best gettering parameter was achieved at 400°C for 35 min of annealing time.
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