成果報告書詳細
管理番号20110000000335
タイトル*平成22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研究(新規バッファ層の開発)
公開日2011/7/28
報告書年度2010 - 2010
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
和文要約和文要約等以下本編抜粋:1.研究開発の内容及び成果等 本研究では、ワイドギャップ(1.4eV程度)CIGSに適合する新規バッファ層の材料とその成形技術、およびバンドギャップチューニング技術の開発を行い、ワイドギャップCIGS太陽電池の高効率化を図ることによって、平成26年度末の最終目標:「フレキシブルCIGS太陽電池サブモジュール(30cm角)にて変換効率18%」を達成することを目標とする。そのために、下記の2課題を実施する。
英文要約Title: The development of high performance flexible CIGS PV modules (Development of Buffer Films and the Wet-Preparation Process)
(FY2010-2012) FY2010 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 of 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 Cu2O 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 ZnO and Cu2O films have been prepared by a chemical bath deposition technique in basic aqueous solutions containing the nitrate, ammonia ion, and thiourea. The bandgap energy and S content of the Zn(O,S) films increased with an increase in the thiourea concentration, and clear linear relationship could be observed between the bandgap energy and S content. The Zn(O,S) films did not show any diffraction peak on the X-ray diffraction spectrum, and the structural characterization was carried out for the Zn(O,S) films and references of ZnO and ZnS by recording the X-ray absorption spectrum in a synchrotron radiation facility (SPring 8). The X-ray absorption near-edge structure (XANES) indicated that the Zn element of Zn(O,S) films was in the state of Zn2+, irrespective of the thiourea concentration. The radial distribution functions (RDFs) calculated by Fourier transformation of XAFS region of the spectra indicated the local structure around the absorption element. The Zn(O,S) films showed a 1st peak at radial distance of 1.5 and 2.0A, which originated from the nearest neighbor elements of oxygen and sulfur, and the intensity ratio of the two peaks changed depending on the S content and related bandgap energy. And, any peak could not be observed at radial distance over 2.5A, suggesting poor long range ordering in the atomic arrangement. The heating at 250 and 500C induced the change of the bandgap energy and the appearance of peaks at radial distance over 2.5A, indicating the improvement of the atomic arrangement. The dependence of the bandgap energy on the S/O ratio calculated from the intensity of two peaks identified as Zn-O and Zn-S bonding for heated Zn(O,S) films was similar to those already reported for sputtering-deposited(sp)-Zn(O,S) films, but there was some difference among as-deposited CBD-Zn(O,S) and sp-Zn(O,S) films. FE-TEM observation indicated that the 20-nm-thick-Zn(O,S) film deposited over entire the CIGS surface.
The CBD film is prepared by hydrolysis of the metal cation released from the ammonia complex by reacting thiourea. We proposed two parameters of solution pH value and total ammonia ion concentration, based on thermodynamic calculation. The increase in the total ammonia concentration induced the suppression of the precipitation formation throughout the solution, and the thin homogeneous Cu(O,S) film deposited over entire the substrate surface.
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