成果報告書詳細
管理番号20090000000294
タイトル*平成20年度中間年報 新エネルギー技術研究開発 太陽光発電システム未来技術研究開発 次世代超薄型多結晶シリコン太陽電池の研究開発(多結晶インゴット)
公開日2009/8/21
報告書年度2008 - 2008
委託先名国立大学法人東北大学
プロジェクト番号P07015
部署名新エネルギー技術開発部 太陽電池グループ
和文要約以下本編抜粋:1. 研究開発の内容及び成果等 [研究目標]次世代超薄型多結晶シリコン太陽電池の研究開発として、共同研究機関のシャープ株式会社が最終目標として掲げる基板厚さ100μm、面積15cm 角相当のセルで変換効率18%の実現のために、 周辺技術として、デンドライト利用キャスト法による多結晶シリコンインゴット成長技術の開発を行う。具体的には1)デンドライト利用キャスト法により作製したシリコンバルク多結晶の高品質化要因の解明2)デンドライト結晶の成長メカニズムの研究および3)デンドライト多結晶シリコン基板の評価を行う。
英文要約Title: Research and Development of Next-generation PV Generation System Technologies, “Next generation ultra-thin mc-Si solar cells (Multicrystalline-Si ingot)” FY2006-FY2009) FY2008 Annual Report This research was performed to establish technologies toward realization of 18% cell efficiency using a 100μm-thick wafer with an area of 15cm-square based on high-quality Si multicrystals. As a fundamental technology to reach the goal, we have developed “dedritic casting method” to produce high-quality Si multicrystals with controlled microstructures. The target of the research is set to clarify (1) underlying mechanisms for improvements in crystal quality of Si multicrystals grown by the dendritic casting method, (2)crystal growth mechanisms of the dendrite crystals and (3) to perform characterizations of wafers based on Si multicrystals grown by the dendritic casting method. In the dendritic casting method, it is of crucial importance to induce dendritic nucleation along the bottom of the crucible at the initial stage of the crystal growth. To realize precise control of the dendritic nucleation, we attempted to clarify the growth mechanisms based on in-situ monitoring of the crystal growth. As a result, we revealed that triangular corners with an angle of 60° are formed at the dendrite tip, and present an original growth model for faceted dendrites to fully explain the growth process. Furthermore, we investigated generation mechanisms of sub-grain boundaries and dislocations in Si multicrystals, which are serious defects to affect solar cell performance. It was found that sub-grain boundaries and dislocations are generated from a grain boundary, and their density was strongly dependent on the shape, density, and coherency of the grain boundary. Based on computer simulation, atomistic structures and electronic states of a grain boundary in Si multicrystals are investigated. The calculated results confirmed that control of microstructures in Si multicrystals is promising for improvement of the solar cell performance. The grown Si multicrystals were sliced into wafers, and they were provided to Sharp, Mitsubishi, and Kyocera for processing into solar cells. The conversion efficiency of 18% was achieved in 10-cm square solar cells using the Si multicrystal ingot with a 15 cm diameter. This was confirmed independently by Sharp and Mitsubishi. Further effort is underway to apply the dendritic casting method to the ingot with a a diameter of 30cm and to establish more precise control of dendrite crystals at the initial stage of the crystal growth.
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