成果報告書詳細
管理番号20110000000654
タイトル*平成22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(構造制御化合物ワイドギャップ)
公開日2011/7/28
報告書年度2010 - 2010
委託先名パナソニック電工株式会社
プロジェクト番号P07015
部署名新エネルギー部
和文要約和文要約等以下本編抜粋:1.研究開発の内容及び成果等 多接合太陽電池で変換効率25%(平成26年度末)を達成するための化合物系ワイドギャップ材料を用いたトップセルの高効率化を目的として、光吸収層のバンドギャップ分布制御、窓層~光吸収層の界面制御、裏面コンタクト制御、光吸収制御等の構造制御の要素技術開発を行い、高効率化技術を実証する。本年度得られた成果を下記に示す。 (1)光吸収層のバンドギャップ制御技術の開発 多接合太陽電池のトップセル開発には、光吸収層のワイドバンドギャプ化が必要である。昨年度CuInS2のInの一部をGaに置換したCu(In,Ga)S2においてGaの固溶率でバンドギャップの制御が可能であることを報告した。
英文要約Title: Research and Development on Innovative Solar Cells (International Research Center for Innovative Solar Cell Program) Exploring Novel Thin Multi-junction Solar Cells with Highly-ordered Structure (Wide-gap Compound Solar Cells with Designed Structure) (FY2008-2012) FY2010 Annual Report
Our objectives are to establish technologies for high efficiency wide-gap compound solar cells as a top cell of multi-junction solar cells achieving an efficiency of 25%. “Bandgap controlling:” We have reported that the bandgap of Cu(In,Ga)S2 (CIGS) thin films can be controlled by Ga content to be suitable for a top cell. However, a high content of Ga which is necessary to control the bandgap of 1.7 ~ 1.8 eV may induce defects in the CIGS bulk, and a decrease of the sulfur content of the CIGS films with increasing the Ga content makes resistivity lower. Several difficult problems must be solved to achieve high efficiency of the CIGS sola cells. We therefore have focused on ZnCuInS2 (ZCIS) as a novel widegap absorber. The ZCIS thin films were prepared by spray pyrolysis deposition using the solution including CuCl2, InCl3, ZnCl3 and thiourea. Cu/In molar ratios were prepared to be constant in the solution. The ZCIS thin films with the different Zn content were prepared by controlling the molar ratios of Zn to the sum of Cu, In and Zn in the solution. The composition ratios of Zn/(Cu+In+Ga) in the films have close agreement with the molar ratios of Zn/(Zn+Cu+In) in the solution. The sulfur content of the films scarcely decreases with increasing Zn content. The bandgap of the ZCIS film lineally widens with increasing Zn content. The wide bandgap of 1.7 - 1.8 eV can be controlled by the Zn/(Zn+Cu+In) ratio of 0.2 - 0.3. The Zn content of the ZCIS films with the bandgap of 1.7 - 1.8 eV is lower than the Ga content of the CIGS films. The ZCIS solar cells were fabricated with a superstrate structure of glass/TCO/TiO2/In2S3/ZCIS/Au. Where, the resistivities of the ZCIS absorbers were controlled by the preparation conditions. An efficiency of the cell increased with decreasing resistivity. This is due to increases of the open circuit voltage (Voc) and short circuit current density (Jsc) with a decrease of the resistivity (an increase of the carrier density) of the absorber. The ZCIS film with resistivity of 6000 ohm-cm had the carrier lifetime of 4ns, measured by the micro-PCD method. This value is longer than the research target of the carrier lifetime by this fiscal year. The ZCIS solar cell with the bandgap of 1.8eV showed an efficiency of 4.4 % (Voc = 0.68 V, Jsc = 13.4mA/cm2, FF (Fill factor) = 0.48, aperture area: 0.34cm2). “Buffer layer:” We have focused on In2S3 films as a buffer layer for CuInS2 based solar cells. The In2S3 films were prepared by spray pyrolysis deposition at the several substrate temperatures using the solution including InCl3 and thiourea with a S/In molar ratio of 3. The In2S3 films had the suitable electric properties such as the low carrier density of 10^12 /cm3 and high hall mobility of 33 cm2/vs as a buffer layer. The solar cell with the CuInS2 film deposited on the In2S3 film showed an efficiency of 4.7 % (Voc = 0.435 V, Jsc = 16.7mA/cm2, FF = 0.645, aperture area: 0.35cm2).
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