成果報告書詳細
管理番号20090000000090
タイトル*平成20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 (配列制御ナノ結晶シリコン)
公開日2009/7/30
報告書年度2008 - 2008
委託先名国立大学法人東京農工大学
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(1)ナノ結晶シリコン層の作製技術の開発 結晶シリコンのサイズを量子サイズ領域(4.7nm以下)にまで微細化し、かつ均一な膜構造を形成するプロセス技術を固めた。具体的には、ウエットプロセス(陽極酸化)およびドライプロセス(Chemical Vapor Deposition:CVD、イオン注入)を用い、それぞれの方法によって得られるナノ結晶シリコン(nc-Si)層について、構造評価などを行った。
英文要約Main Theme: Silicon-based Multi-junction Solar Cell
Sub-theme: Controlled Nanocrystalline Silicon Material
(Tokyo University of Agriculture and Technology, N. Koshida)
1)Development of nc-Si Film Fabrication Technology Fabrication technology of quantum-sized nanocrystalline silicon (nc-Si) layer has been developed by either wet-processing or dry-processing approaches. In accordance with structural characterizations, highly uniform nc-Si layer can be produced by wet (electrochemical anodization) technique under the appropriate conditions. In this case, in addition, control of the anodization current makes it possible to peal out nc-Si films from the substrate and to obtain self-standing nc-Si layers. These films are directly applicable to a top cell material for multi-junction photovoltaic device.
2)Optical characterizations The optical properties of fabricated self-standing nc-Si films were evaluated in terms of photoluminescence (PL), optical transmission spectrum, and photoconduction (PC) effect. The experimental results confirmed that a significant band gap widening occurs in nc-Si films, and that both the red-band PL intensity and stability are remarkably enhanced by surface passivation based on high-quality thin oxides. The evidence of band gap widening has been also observed in PC spectra. The fact that reducing interfacial trap density between nc-Si dots enhances the PC sensitivity suggests the potential of this material as a component for photo-excitation and subsequent transport of carriers.
3) Band gap control Based on the above results, a blue shift of band gap from the visible range to the near-ultra-violet region was pursued by further modification of the surface oxidation conditions. Key issue is to form a high-quality tunnel oxide without affect on the carrier transport. By appropriate combination of rapid thermal oxidation with high-pressure water vapor annealing, an efficient and stable blue PL was observed with no contribution of the red emission, including a blue shift of transmission spectra.
In summary, the experimental data suggest that band gap engineering holds in the nc-Si layer, and that nc-Si would meet the requirements for the top cell material of silicon based multi-junction device. High controllability of the film thickness and area in wet anodization technique is attractive from a practical viewpoint. More detailed optical and electrical analyses will be conducted in the forthcoming years toward the actual applications.
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