成果報告書詳細
管理番号20140000000639
タイトル*平成25年度中間年報 太陽エネルギー技術研究開発 太陽光発電システム次世代高性能技術の開発 フレキシブルCIGS太陽電池モジュールの高効率化技術 (新規バッファ層の開発)
公開日2015/2/19
報告書年度2013 - 2013
委託先名国立大学法人豊橋技術科学大学
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 development of high performance flexible CIGS PV modules (Development of Buffer Films and the Wet-Preparation Process)
(FY2010-2014) FY2013 Annual Report

The research and development program was to start in fiscal 2010 in order to fabricate Cu(InGa)Se2 (CIGS) photovoltaic devices with conversion efficiency over 16%. Toyohashi University of Technology (TUT) plays a role for developing new buffer layer and the wet preparation process, and two subjects of the optimization of structural characteristic of the buffer layers and development of technique to control the CBD reaction are carried out. Two types of oxides of ZnO and Cu-O are used as the buffer layer alternative to the CdS currently used as the buffer layer in the CIGS solar cell, because of the ionization energy of 3.8 and 3.3 eV, respectively.
The Zn(O,S,OH) layer is prepared by a chemical bath deposition (CBD) technique in basic aqueous solutions containing the zinc nitrate hydrate, ammonia ion, and thiourea, and the local structures around the Zn atom in the Zn(O,S,OH) layer has been investigated based on radial distribution functions (RDFs) calculated from the X-ray absorption spectra taken in a synchrotron radiation facility (SPring 8). The local structure around the Zn atoms strongly depended on the substrate materials such as CIGS and soda-lime glass substrates, and the Zn(O,S,OH) layer prepared on the CIGS substrate had a layered structure of the upper Zn(OH)2 layer and lower highly crystallized Zn(O,S) layer near the CIGS substrate. The conversion efficiency of the CIGS solar cell with the Zn(O,S,OH) layer was improved from 6.8% to 13.7% by the simple immersion of the Zn(O,S,OH) layer into the diluted ammonia water solution to eliminate the upper Zn(OH)2 layer with large conduction band offset around +1.0eV. The conversion efficiency of 15.5% has been obtained for the CIGS solar cell with the Zn(O,S,OH) buffer layer by optimizing the preparation condition including the solution formulation and deposition time. The improvement of the conversion efficiency was induced by improvement of the homogeneity and decreasing the thickness of the Zn(O,S,OH) layer.
The thermochemical simulation technique built in the CBD process for the Cu(O,S) layer preparation has been applied for the Zn(O,S,OH) CBD deposition. The CBD deposition was occurred both by the supersaturation of ZnO, ZnS, and Zn(OH)2 by shifting the solubility curves with the solution temperature and by the electrochemical reaction of the Cu dissolution from the CIGS substrate. The solution formulation without the precipitation during the CBD deposition has been developed based on the thermochemical simulation, and it was confirmed the deposition of the smooth Zn(S,O) layer on the CIGS substrate.
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