成果報告書詳細
管理番号20090000000283
タイトル*平成20年度中間年報 革新的太陽光発電技術研究開発(革新型太陽電池国際研究拠点整備事業) ポストシリコン超高効率太陽電池の研究開発(エピタキシャル成長技術)
公開日2009/8/21
報告書年度2008 - 2008
委託先名シャープ株式会社
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 変換効率50%実現のポテンシャルのあるIII-V族化合物材料による多接合型セルについて高効率化の検討を行う。図1に示したのは平成26年度にかけてNEDOプロジェクトで検討を予定している高効率化達成へのアプローチを示したものである。本計画では格子不整合系の3接合/4接合セル、量子ドットを挿入した3接合/4接合セル、InGaAsN材料を用いた4接合セルを東京大学と豊田工業大学と協力して開発する。 平成22年度の中間目標は非集光時効率33%、集光時効率42%であるが、平成20年度は変換効率33%以上を目標に格子不整合系の逆エピInGaP/GaAs/InGaAs(1eV)3接合セルにおける特性改善に注力した。
英文要約Title:R&D on innovative Solar Cells. Post-silicon solar cells for ultra-high efficiencies (epitaxitial technology) (FY2008-FY2010) FY2008 Annual Report III-V compound solar cells are very attractive because they have potential reaching 50% efficiency. In the NEDO project, development on invert lattice mismatch cells, 3 or 4 junction cells by utilizing quantum well/dot, and 4 junction cells using InGaAsN material, are proceeding under the collaboration with University of Tokyo and University of Toyota Technological Institute. We focused on development of invert triple junction cells this year to realize more than 33% efficiency under 1sun. Epitaxitial technology was developed for invert InGaP/GaAs/InGaAs(1eV) cells. Because an InGaAs(1eV) bottom cell has large lattice mismatch to the substrate, design and growth condition of the graded buffer layers to relax strain were investigated. Performance of the invert InGaAs single cells was evaluated prior to invert triple junction cells. Voc as high as 0.59V was achieved by improving InGaP based step-graded buffer layers for the InGaAs cell with 0.98eV band gap. Small difference of 0.39eV (= 0.98eV - 0.59eV) suggests that quality of the invert InGaAs single cells are as good as that of lattice-matched GaAs based cells. Then invert triple junction cells were successively fabricated. Voc close to 3V and the efficiency over of 33.5% have been realized under 1sun at this moment. By X-ray measurement it was confirmed that InGaP buffer layers and InGaAs layer suffered compressive strain and tensile strain respectively, which showed bottom cell layers were well balanced in the stress point. TEM measurement results also clarified that any dislocation was not observed in the InGaAs layer.
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