成果報告書詳細
管理番号20120000000147
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(酸化物ワイドギャップ)
公開日2012/6/20
報告書年度2011 - 2011
委託先名豊橋技術科学大学
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: The Innovative Photovoltaic Technology Research and Development Program. Development of Multi-Junction Thin Film Solar Cells using a Smart Stack Technique
(Oxide Semiconductors with Wide Bandgap Energy) (FY2008-2012) FY2011 Annual Report

The innovative photovoltaic technology research and development program were to start in fiscal 2008. To fabricate photovoltaic devices with conversion efficiency over 40%, multi-stacked solar cell composed of three compound semiconductor photovoltaic devices with different band gap energy is developed. Toyohashi University of Technology (TUT) plays a role of developing wide band gap oxide semiconductors appropriate to the light-absorbing layer and the single solar cell applied to the top cell in multi-stacked solar cell. A p-type semiconductor Cu(II)O layer was prepared by using a thermodynamically designed solution formulation, and the bandgap energy was controlled ranging from 0.95 to 1.65eV by adjusting the preparation conditions. And, (111)-oriented Cu(I)O semiconductor was prepared by electrochemical heteroepitaxial growth on (111)-oriented Au/(100) Si wafer. The excellent (002)-oriented Cu(II)O layer has been prepared by electrochemically heteroepitaxial growth on (111)Au/Si wafer and showed excellent photoactivity of large photocurrent density and quick response. In fiscal 2011, an annealing treatment has been performed to improve the quality of the oriented Cu(I)O and Cu(II)O layers prepared by the heteroepitaxial growth on the Au/Si substrate. The annealing at temperatures over 623K induced the solid reaction between the copper oxides and Au layers, and the quality estimated from photoluminescence and Hall effect measurement deteriorated for both the copper oxides. The Cu(II)O layer showed almost constant photocurrent density irrespective of the annealing temperature up to 573K, and the photo-response improved from about 2 sec to 0.2 sec by raising the annealing temperature. The resistivity of the Cu(I)O layer decreased with increase in annealing temperature to 573K, and then increased. The mobility increased with increase in annealing temperature up to 573K, and then decreased. The carrier concentration decreased with increase in annealing temperature, and the change was consistent with the change in intensity of visible light emission due to the Cu vacancies. The carrier concentration was very low of the order of 1014cm-3, and the introduction of Ag impurity into the Cu2O layer induced the increase in carrier concentration to 1016cm-3, suggesting that the doped Ag impurity act as an acceptor in the Cu2O. Both the Cu(II)O and Cu(I)O layers were reduced to metallic Cu during the preparation of n-ZnO layer by sputtering, and the diodes showed poor rectification feature in dark and no photovoltaic performance due to the existence of metallic Cu impurity at the heterointerface. The copper oxide diodes with n-ZnO layer prepared by an electron-beam evaporation showed an excellent rectification feature and slight photovoltaic performance under AM1.5G illumination.
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