成果報告書詳細
管理番号20130000000456
タイトル*平成24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2013/6/22
報告書年度2012 - 2012
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-FY2012) FY2012 Annual Report

Since we, Showa Shell Sekiyu K.K., had already achieved a conversion efficiency of 17.8% on a 30 × 30 cm2-sized submodule, which exceeded our intermediate target for FY2012, we have been focusing on following items to achieve our final target, an efficiency of 18% on a 30 × 30 cm2-sized submodule in 2014. We re-examined the sulfurization after selenization (SAS) process, which is our proprietary technology to form p-type CuInSe2-based light-absorbing layer, in order to improve the absorber quality (or Voc × Jsc) by optimizing the compositional profiles of Ga and S within the layer. SAS process involves difficulty in controlling Ga profile; it tends to be a single graded profile with high and low Ga composition at back and front side, respectively. Hence, in the SAS process, it is unable to form double graded Ga profile as in the co-evaporation technique. Therefore, we realize the double graded band profile with both Ga and S profiles. After optimizing the compositional profiles of Ga and S, we obtained maximum value of Voc × Jsc with Eg(min) = 1.07 eV, which is smaller than Eg(min) = 1.15 - 1.20 eV, which is previously thought to be an optimum value for the minimum band gap. Though we have achieved the conversion efficiency of 17.8% on a 30 × 30 cm2-sized submodule in last year, it is essential for gaining higher efficiency in the future to improve intrinsic conversion efficiency on a small cell without extrinsic issues originated from the large area module. Thus, we have started to study high efficiency small area cells, which should play a leading role for high efficiency large area submodules. If the cells were made by using some techniques specialized for small area cells, it is subsequently required to develop a new large area process. Therefore, we have formed all layers with 30 × 30 cm2-size and evaluated small area cells obtained by dividing the large substrate. In this year, we have tuned the thickness of ZnO:B window layer and the Al front electrode pattern (designed by AGU) as a preliminary study and achieved a conversion efficiency of 19.7% (certificated by AIST), which is the highest efficiency in Japan. Also, this is the world record efficiency with Cd-free buffer, that overtakes NREL’s 18.6% (certificated) and ZSW’s 19.1% (uncertificated). In order to review the key point, we have compared our device parameters with those from the champion cells exceeding 20% efficiency in ZSW and NREL. As compared with ZSW’s champion cell, we found that our device is inferior in Voc × Jsc while FF is comparable. On the contrary, there is a substantial gap in FF when comparing our device with NREL’s champion cell. In the next year, we will pursue achieving FF over 0.8 and reducing Voc deficit by optimizing band offset between absorber layer and buffer layer as well as optimizing band profile of the absorber layer.
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