成果報告書詳細
管理番号20140000000186
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 CIS系薄膜太陽電池の高効率化技術の研究開発
公開日2014/8/23
報告書年度2013 - 2013
委託先名昭和シェル石油株式会社
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: Research and Development of High Efficiency CIS Thin-Film Submodules (FY2010-FY2014) FY2013 Annual Report

In FY2013, we have focused on the following items to achieve the final target in FY2014, a conversion efficiency of 18% on a 30 × 30 cm2-sized submodule and 17.5% using an absorber layer having the thickness reduced by 20% as compared to the high-performance device. (1) The reduction of the open-circuit-voltage deficit. In CIS-based solar cells, “Voc deficit” (the difference between the absorber bandgap and the open-circuit voltage) is known to be one of the main reasons for the lowering the conversion efficiency. To reduce the Voc deficit, by adjusting the process for forming the absorber layer, the carrier lifetime of the absorber was improved and the bandgap profile was optimized. As a result, the lowest Voc deficit of 0.37 V has been achieved. (2) The improvement of the uniformity on 30 × 30 cm2-sized substrates. While the conversion efficiency of our small-sized cells reached 19.7%, that of submodules was only 17.8%. One of the origins for this gap is a non-uniformity of the physical properties in each constituent layer. To improve the uniformity in the absorber layer, we have modified the selenization and sulfurization process. As a result, the standard deviation of the efficiency of small cells obtained from a 30 × 30 cm2-sized substrate has been reduced to 0.3% in absolute value. (3) The improvement of carrier mobility in the transparent conductive oxide layer. We use the boron-doped zinc oxide (BZO) deposited by MOCVD method as the transparent conductive oxide. By adjusting the deposition process of BZO, we have succeeded in increasing carrier mobility. Using this technique, the carrier density can be reduced with keeping the sheet resistance of BZO constant. Hence, we have achieved in the reducing both the resistive loss and the light absorption loss in BZO. (4) The reduction of the absorber thickness to reduce the production cost. By decreasing the absorber thickness, the material cost can be reduced. We have fabricated the CIS solar cells having the absorber thickness reduced by 20%-50% as compared to the standard absorber with high performance. The emerged challenging issues are the absorption loss and the difficulty in controlling the compositional profile by the reduction of the thickness. So far, a conversion efficiency of 16.7% with the thickness reduction of 30% has been achieved.
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