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Direct production process of low cost solar-grade silicon feedstock for multi-crystalline solar cells

用于多晶太阳能电池的低成本太阳能级硅原料的直接生产工艺

基本信息

批准号：
07505021
负责人：
MAEDA Masafumi
金额：
$ 8.06万
依托单位：
The University of Tokyo
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (A)
财政年份：
1995
资助国家：
日本
起止时间：
1995 至 1996
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-07505021/
关键词：
Refining Silicon Solar Cell Solidification Electron beam Segregation

项目摘要

In this study, the new process was developed for low cost silicon feed stock for multi-crystalline solar cells. Low cost metallurgical-grade silicon (MG-Si) was the raw material for the process. Modified electron beam (EB) and plasma arc (PA) remelting techniqued were applied for the elimination of impurities. Continuous solidification was employed to remove transition metals.Button melting techniquePlasma arc of Ar-H_2O mixture was applied to eliminate boron by forming boron oxide or hydroxide vapor. Boron content reached about 1ppmw within 3.6 K seconds at 0.19 to 0.39vol. %H_2O.When H_2O content was increased to 1.24vol. % boron content was lowered to below 1 ppm within 900sec.The impurities such as carbon, phosphorus, calcium and aluminum in MG-Si were removed by EB treatment under 10^<-2> Pa for thirty minutes. Ninety percent of carbon was eliminated and the content reduced to 15ppmw, 75% of aluminum was eliminated and the content decreased to 470ppmw, 89% of calcium was removed and the content decreased to 150ppmw, and 93% of phosphorus was removed and the content decreased to 3ppmw at 5.0kW.Unidirectional continuous casting of siliconContinuous casting of silicon in the vacuum was performed. Transition metals such as iron and titanium were removed by segregation. The iron content leached to less than 1/30 for the ingot length of more than 50% of the ingot height at the casting rates of 2mm/min. This method will be one of the silicon source for solar grade silicon.

在这项研究中，新工艺的开发，为低成本的硅原料的多晶太阳能电池。低成本的冶金级硅（MG-Si）是该工艺的原材料。采用改进的电子束（EB）和等离子弧（PA）重熔技术去除杂质。采用连续凝固法去除过渡金属，采用扣式熔炼技术，利用Ar-H_2 O混合气体等离子弧形成硼的氧化物或氢氧化物蒸气去除硼。硼含量在0.19 - 0.39vol范围内在3.6K秒内达到约1 ppmw。%H_2O。当H_2O含量增加到1.24vol.在900秒内将硼含量降低到1 ppm以下。在10 μ Pa下通过EB处理30分钟去除MG-Si中的杂质如碳、磷、钙和铝<-2>。在5.0kW时，除碳90%，含量降至15 ppmw;除铝75%，含量降至470 ppmw;除钙89%，含量降至150 ppmw;除磷93%，含量降至3 ppmw。过渡金属如铁和钛通过偏析除去。在2 mm/min的浇注速度下，当锭长大于锭高的50%时，铁的浸出率小于1/30，是太阳能级硅的硅源之一。