成果報告書詳細
管理番号20120000000810
タイトル*平成23年度中間年報 新エネルギー技術研究開発/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2012/11/28
報告書年度2011 - 2011
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部
和文要約和文要約等以下本編抜粋:
1.研究開発の内容及び成果等
本プロジェクトでは、集光時効率45%の達成を目標に逆積み3接合セルの開発と、集光時効率48%の達成を目標に4接合セルの開発を行う。平成20年度より開発中の逆積み3接合セルは、バンドギャップ(Eg)の組合せをそれぞれEg =1.88eV、1.42eV、0.98~1.00eVと最適化した、InGaPトップセル、GaAsミドルセル、InGaAsボトムセルで構成している。本構造セルでは図1に示したようにInGaAsボトムセルの格子定数が基板や他のサブセルに比べて約2%大きいため、格子整合系のトップセルとミドルセルを最初に成長し、格子定数を徐々に変化させたグレーディッドバッファ層を介して格子不整合系のボトムセルを最後に成長する。
英文要約Title:R&D on innovative Solar Cells Post-silicon solar cells for ultra-high efficiencies (epitaxitial technology) (FY2008-FY2012) FY2011 Annual Report
Development on invert lattice mismatch triple junction cells composed of InGaP(1.88eV) top cell, GaAs(1.42eV) middle cell and InGaAs(0.98 ~ 1.00eV) bottom cell has been continuously done from FY2008. During the investigation in FY2008-FY2010, 35.8% efficiency which was the world record under 1sun was realized (confirmed by National Institute of Advanced Industrial Science and Technology(AIST)) and 42.1% efficiency was also confirmed under 230suns in house measurement. This year we tried to further improve the performance of concentrator cells in order to achieve the target value of 45% in FY2012. We improved the maximum concentration ratio by reducing series resistance, especially the resistance in tunnel junctions. By optimizing carrier concentrations and growth condition of the n-InGaP (Te-doped) layer and the p-AlGaAs (C-doped) layer which are components of the tunnel junction layers, the resistance in tunnel junctions was reduced to around 20mΩ from former 80mΩ in a 4mm x 4mm size cell. As a result, 43.5% efficiency and 42.5% efficiency were confirmed at 300x to 500x concentration ratio in cells with 200μm grid pitch and at 450x to 700x concentration ratio in cells with 125μm grid pitch, respectively. It is necessary to further improve maximum concentration ratio up to 1000x by reducing series resistance components other than the resistance in tunnel junctions to realize 45% target efficiency. We also evaluated 1sun characteristics of a series resistance reduced cell. The cell was designed as around 1cm x 1cm size and 1mm grid pitch to match non concentration condition. 36.9% efficiency which is the new world record under 1sun was confirmed by AIST. The improvement of efficiency was thought to be by F.F. improvement (F.F. was 0.853 in the former 35.8% cell and 0.875 in the 36.9% new cell). We also started the investigation of 4 junction cells by several approaches.
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