成果報告書詳細
管理番号20110000000698
タイトル*平成22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)/低倍率集光型薄膜フルスペクトル太陽電池の研究開発(グラフェン透明導電膜)
公開日2011/7/30
報告書年度2010 - 2010
委託先名富士電機株式会社(旧:富士電機ホールディングス)
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
1.1 研究開発の目標
本テーマ(グラフェン透明導電膜)では、低倍率集光型薄膜フルスペクトル太陽電池を実現するために必要不可欠な、可視光のみならず赤外領域においても透過率が高い透明導電膜の開発することを目的に、今年度、グラフェン製膜技術の開発とグラフェンを透明導電膜へ適用する技術の研究開発を行い以下の値を達成する。
・導電率:6×103 S/cm 以上
・透過率: 80% 以上 @ 380 – 2000 nm
1.2 研究開発の内容および成果
(1)はじめに
近年、CVD によって遷移金属上(Ni、Cu)に成長したグラフェンを転写プロセスによって任意の基板に転写することが可能となり、大面積で高品質なグラフェンが作製できるため産業化のひとつの手法として非常に注目を集めている1-3)。しかし、CVD の製膜条件や、作製したグラフェンの電気特性についてはその詳細が分かっていないのが現状である。そこで、我々はCVD によるグラフェンの成長とこのグラフェンの電気伝導特性について詳細に研究を行い、2010 年度の目標を達成した。以下に、それらの成果の概要を報告する。
英文要約Title : Thin Film Full Spectrum Solar Cells with Low Concentration Ratios (Graphene Ttransparent Conductive Films) (FY2008-2012) FY2010 Annual Report
Graphene, a mono-layer carbon film with honeycomb lattice structure, is very attractive as a candidate for transparent conductive film (TCF). It shows a high transparency even in the infrared range, because excess carrier doping is not required to achieve high conductivity. In spite of its high potential, however, it is difficult to fabricated large area graphene sheets by the mechanical cleaving method, and was too small to apply to the TCF. In 2010, we have studied to enlarge the size of graphene sheets using chemical vapor deposition (CVD) and to form the graphene TCF with them as follows: (1) Growth of graphene by chemical vapor eposition. We have optimized the growth condition of CVD to control the film quality and uniformity. Cu foil with an area of 10mm x 10mm and a thickness of 100 μm was used as a substrate. Since a number of scratches exist on the surface of as-received Cu foils, we provided both mirror polished and not mirror polished substrates. Graphene was deposited on them in a conventional tubular quartz reactor, used material gas was CH4 and was introduced into the reactor. In the CVD, the substrate temperature was 1000 degrees Celsius, and the gas pressure was in the range of 1-30 Torr. From Raman spectrum of obtained CVD graphene, the D peak, which corresponds to disorder in the honeycomb lattice, decreased in the mirror polished Cu foil samples. This result indicates that flatness and homogeneity of the Cu foil surface influence the quality of graphene. (2) Electrical properties of CVD graphene. The electrical properties of CVD graphene was measured by Hall effect with van der Pauw settings. Graphene on PMMA (Poly(methyl methacrylate), that is the one after etching Cu substrate from the sample, showed lower sheet resistances (several hundred Ω/sq). On the other hand, the sheet resistance increased by an order of magnitude in the graphene transferred on SiO2 and quartz substrates. This increase in sheet resistance was mainly due to reduction in carrier mobility. We believe that generation of defects during the transfer process is main cause and it is the next challenge to improve this process.
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