成果報告書詳細
管理番号20120000000160
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)高度秩序構造を有する薄膜多接合太陽電池の研究開発
公開日2012/6/20
報告書年度2011 - 2011
委託先名産業技術総合研究所
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: Exploring multi-junction thin-film solar cells with highly ordered structures (FY2008-2012) FY2011Annual Report

In order to obtain efficiency over 40%, we have studied highly ordered novel materials for optimized band gap and mechanically stacked two-terminal multi-junction solar cells. As highly ordered materials, many types of novel materials and structure, such as quantum dots (QDs), nanostructure (silicon, carbon), single-crystalline organic, etc, are studied. To achieve higher efficiency, the light management technologies including photonic structure, utilization of plasmon effect are also the research themes. Novel mechanical stacking technology is a must for fabricate two-terminal solar cell structure. Followings are some of the major results of research themes carried out in FY2011. 1-1-1: Development of mechanical stack and device fabrication technologies: A new direct bonding technique with conductive nanoparticle alignment was developed. With this method, bonding resistance of below 10 Ωcm2 and optical absorption loss of 5 % were obtained simultaneously. A new direct bonding method utilizing solid-phase crystallization of transparent conductive oxides was also studied. It was found that control of surface roughness, crystallite size during crystallization, and outgas during heating are important to realize high bonding strength. 1-2-1: Development advanced light management technologies: We have proposed a flattened light scattering substrate (FLiSS) which scatters the incident light due to the distributed refractive index in plane, and demonstrated its light trapping effect. It was clarified by the simulations that the optimized FLiSS enhances the IR response in thin-film Si solar cells by 50% compared with the present structure. For better implementation of the plasmonic effect in solar cells, a chemical synthesis and dispersion process of Ag nano-particles were developed. The light trapping by the Ag nano-particles has been demonstrated by the improved IR response in thin-film Si solar cells. 2-1-1: Development of Si-Ge bottom cells: High quality crystalline SiGe thin film with low dislocation density was successfully grown on Si substrate inserting compositional graded buffer layers between the epitaxial layer and the substrate. As a device fabrication technology, the heterojunction Ge solar cells were fabricated by depositing amorphous Si films on Ge substrates. The temperature coefficient of the conversion efficiency was found to be small (-0.61%/oC) even under near-infrared light illumination. 3-2-1: Development of compound semiconductor top cells: Wide bandgap solar cells with Cu(InGa)(SSe)2 (CIGSSe) compound semiconductor have been developed. Employing a radical beam evaporators, which have high potential to control the flux intensity of sulfur beam, as a source of sulfur, we succeeded precise control of compositional ratio S/(Se+S) in CIGSSe alloys, and obtained the CIGSSe alloys with bandgap energy Eg of higher than 1.7 eV. Conversion efficiency of 7% was obtained by the solar cell utilizing such CIGSSe films with Eg of 1.7 eV.
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