成果報告書詳細
管理番号20130000000768
タイトル*平成24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) 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2014/5/9
報告書年度2012 - 2012
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
英文要約Title: R&D on innovative Solar Cells (International Research Center for Innovative Solar Cell Program) "Research and Development of Post-silicon solar cells for ultra-high efficiencies (epitaxial technologies)" (FY2008-FY2014) FY2012 Annual Report
Development on inverted 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 continued since FY2008. During the investigation in FY2008-FY2011, 36.9% efficiency which was the world record under 1sun was realized (confirmed by National Institute of Advanced Industrial Science and Technology(AIST)) and 43.5% efficiency was also confirmed under 300x to 500x concentration ratio 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 current in the cells by reducing optical loss. GaAs contact layer under grid electrodes acts as an absorber for short wavelength light sensitive for the top cell. Spectral response in the current inverted lattice mismatch triple junction cells showed that the current was limited in the top cell. Thus narrowing the width of GaAs contact layer was thought to be effective to reduce optical loss and improve current. We fabricated 6μm width from former 9μm and the optical loss was reduced to 3.0% from 4.8% in cells with 200μm grid pitch. The ratio of current improvement was expected as +1.9% for the case. As a result, 43.8-44.2% efficiencies were confirmed at 400x to 600x concentration ratio in cells with 200μm grid pitch in house measurement. However it is necessary to further improve the current by more than 2% to realize 45% efficiency. The composition change of AlInP window layer of the top cell and the increase of the thickness of InGaP base layer of the top cell were found to be promising to improve current by more than 2%. We are now investigating those approaches. We also improved 1sun characteristics of cells designed as around 1cm x 1cm size and 1mm grid pitch to match non concentration condition. 37.9% efficiency which is the new world record under 1sun was confirmed by AIST. The improvement of efficiency was due to increase of Voc by optimizing the bandgap of InGaAs bottom cell (Voc was 3.006V in the former 36.9% cell and 3.065V in the 37.9% new cell). In addition we investigated concentrator modules using inverted lattice mismatch triple junction cells. The efficiency of a mono module with one lens was estimated as 32.2% in house measurement. We have started the field test of concentrator modules composed of 24 mono modules in Arizona USA from March 2013. We are planning to obtain field data until the end of FY2014.
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