成果報告書詳細
管理番号20120000000560
タイトル*平成23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(室温レーザードーピングプロセスの研究開発)
公開日2012/12/26
報告書年度2011-2011
委託先名国立大学法人奈良先端科学技術大学院大学
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:基板表面の形状を示す。照射前表面が粗い場合、表面に
はクレーター状の凹凸が観察され(左図)、これが少数キャリアの再結合中心として悪影響を与えることが分かった。
英文要約itle : High Performance PV Generation System for the Future. R and D on Ultimate Wafer-based Si Solar Cells. / Recovery of silicon powder from multi-wire-saw sludge and reproduction to feedstock (FY2010-FY2012) FY2011 Annual report
(1) Development of separation process of silicon powder and impurities. (1-1) Characterization of waste coolant. From TG measurements, in all coolants, the mass was decreased with increasing temperature, and was kept at constant when the temperature exceeds 200 C. From DTA, two peaks were recognized at around 100 C and 200 C. The result indicated that the all coolants consisted of water and glycol series with the boiling temperature of around 200 C. The viscosity of the each coolant was significantly different. Since the coolants consisted of water and glycol series, we considered that the difference of viscosity is due to dilution ratio. Then, viscosities of various diluted solutions were measured. The viscosity was drastically decreased with dilution ratio increase. It can be concluded that the difference of coolant viscosity was due to the difference in the ratio of coolant components.(1-2) Characterization of silicon powder. The particle size distributions of the solid materials in the waste coolants were measured by DLS method. Although the range of particle sizes was almost same (0.03~6 um), the distribution of each sample was different. Over 50 vol% of solid materials were retrieved from each coolants by pressurized filtrations with a pore size of 0.45 um. (1-3) Characterization of filtration. In order to explain experimental results of pressurized filtration, we proposed a model equation. Figure 4 shows the filtration volume as a function of filtration time. The calculated results using the model equation correspond with the experimental results. Then, we used the equation to forecast a filtration time when the waste coolant was diluted by water. From the result of forecast, optimum dilution ratio is 1. In order to confirm the forecast, filtration experiments with diluted waste coolants were carried out. The experimental result was consistent with the forecast. (2) Development of reproduction process of feedstock.(2-1) Impurities in retrieved silicon powder. The metal contents in retrieved Si were measured by ICP-MS. The metal concentrations are too high to use as feedstock for crystal growth. However, the quality of the retrieved Si is better than that of metal-grade Si. Therefore, after refining by directional solidification, the metal concentrations will be decreased, and they will be low enough for solar-grade (SOG) Si. (2-2) Compaction of silicon powder. To improve heat transference and to facilitate handling, the retrieved Si powders were shaped into pellets by pressure. The maximum filling fraction of about 50% was obtained at about 0.5GPa. (2-3) Melting and re-crystallization. A shaped Si was set in a Si3N4- coated Al2O3 crucible, and was heated at 1550 C for 1 hour in Ar atmosphere. The shaped Si was completely melted during heating.
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