成果報告書詳細
管理番号20140000000679
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 極限シリコン結晶太陽電池の研究開発 (産業開発プラットフォームの構築(物性評価)
公開日2015/2/19
報告書年度2012 - 2012
委託先名学校法人明治大学
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: High Performance PV Generation System for the Future R and D on Ultimate Wafer-based Si Solar Cells. (Common industrial platform (material evaluation)) (FY2010-FY2014) FY2012 Annual Report

The common industrial platform can be categorized into following three areas, i.e. the evaluation platforms for the fabrication processes of 1) solar cells, 2) high performance multi-crystalline substrates, and 3) low cost single crystalline substrates. 1) For the cell process, we used ion shower doping to fabricate n+ layer for the selective emitter structure. The system has large beam area, therefore realizes high through-put more than 1000 wafers/hour. The fabricated cell performance, both Voc and Isc were higher than the reference. Metal contamination and doping variability could be negligible. 2) Quantification of donor and acceptor impurities in the concentration range of 1 - 5 x 1017 cm-3 has been realized on the basis of the analysis of photoluminescence (PL) due to impurity cluster bound excitons (ICBE). The ICBE peak shifts monotonically with the P concentration in that concentration range. It should be pointed out that the data points lie nearly on a straight line for the samples from different sources. This demonstrates that the relationship is universal and can be used as a calibration curve. We demonstrated high-speed PL imaging for not only band-to-band but also multiple deep-level emissions in a mc-Si solar cell. We used a cooled InGaAs camera with a photosensitive range of 900 - 1700 nm equipped with band-pass filters for the selective detection of various deep-level emissions originating from dislocations and O precipitates. The exposure time for imaging was only 1 - 10 sec., which was about 1/50 of the time required for conventional PL mapping. 3) Light elements precipitates in mc-Si are detrimental for solar cell application. N is introduced in Si melt from crucible coating and precipitates in several morphology. We have studied the butterfly colonies of precipitates and found fiber and filament type precipitates. EDX measurement revealed that they are composed of Si and N, suggesting Si3N4 precipitates. The detailed observation of these precipitates gives useful information on the Si melt convection. Residual strain is another important factor for Si process because they often give fracture of wafers. The distribution of residual strain in seed cast ingot has been investigated by SIRP method. This study suggests the control of cooling process is the most important to reduce the residual strain in cast Si ingots. For the suppression of light element impurities and the crystalline defects, we fabricated the crystalline ingot under suppressed wettability, called “liquinert conditions”. The surface of grown ingot clearly showed metallic luster and relatively large grains from bottom to top. We believe that it is important to suppress the wetting properties for fabrication of high quality crystalline ingot.
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