| Project/Area Number |
18K05009
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Multi-year Fund |
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| Section | 一般 |
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| Review Section |
Basic Section 31020:Earth resource engineering, Energy sciences-related
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| Research Institution | Tohoku University |
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Principal Investigator |
Yutaka Ohno 東北大学, 金属材料研究所, 准教授 (80243129)
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| Co-Investigator(Kenkyū-buntansha) |
森戸 春彦 東北大学, 金属材料研究所, 准教授 (80463800)
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| Project Period (FY) |
2018-04-01 – 2021-03-31
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| Project Status |
Completed (Fiscal Year 2020)
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| Budget Amount *help |
¥4,290,000 (Direct Cost: ¥3,300,000、Indirect Cost: ¥990,000)
Fiscal Year 2020: ¥1,300,000 (Direct Cost: ¥1,000,000、Indirect Cost: ¥300,000)
Fiscal Year 2019: ¥910,000 (Direct Cost: ¥700,000、Indirect Cost: ¥210,000)
Fiscal Year 2018: ¥2,080,000 (Direct Cost: ¥1,600,000、Indirect Cost: ¥480,000)
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| Keywords | 電圧誘起ナトリウム集積 / シリコン太陽電池 / メガソーラー |
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| Outline of Final Research Achievements |
Transmission electron microscopy combined with ab initio calculations reveals that, Na atoms would agglomerate at stacking faults (SFs) under an electronic interaction, reducing the SF formation energy. The energy would decrease with the decrease of the Fermi level: it is reduced by more than 10 mJ/m＾2 in p-type Si, whereas it was barely reduced in n-type Si. Owing to the energy reduction, Na atoms agglomerating at SFs in p-type Si are stable compared with those in n-type Si. It is also shown that Na atoms preferentially interact with grain boundaries (GBs), as well as with SFs, and the degree of the GB interaction would be related to the GB energy; the degree is high for GBs with a high GB energy such as random-angle GBs, and it is low for GBs with a low GB energy such as ∑3{111} GBs and SFs.
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| Academic Significance and Societal Importance of the Research Achievements |
太陽電池中のナトリウムの移動・集積過程は、モジュール構造（ガラス、封止材の材質）、セル構造（基板、極性、キャリア濃度）、外部環境（雰囲気、電圧、光照射の条件）に複雑に依存する。セル化・モジュール化されていないシリコン単結晶へ意図的に積層欠陥とナトリウムを添加することで、シリコンの極性やフェルミ準位、小数キャリア密度に依存するナトリウムの移動・集積の素過程が初めて明らかになった。また、ナトリウムは積層欠陥だけでなく一般の粒界とも反応し、その反応性は粒界エネルギーに依存することも分かった。これらは、ナトリウムに関連する電圧誘起劣化が生じにくいシリコン太陽電池セルを設計する上で重要な情報である。
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