文档介绍：铸造多晶硅边皮料的杂质分布研究
摘要
目前,在铸造多晶硅中的生产中,铸锭成品率大概在65%—70%,而另外30%—35%的硅料则不能直接用于生产太阳能电池片,这部分硅料有边皮料,头尾料等。主要因为铸造多晶硅边皮料和头尾料中杂质和缺陷太多,高浓度的杂质,是影响太阳能电池转换效率的重要因素,因此深入地研究铸造多晶硅中杂质的种类及分布情况,分析它们对多晶硅晶锭结晶学及电学性能的影响,不仅有利于生长出高成品率的铸造多晶硅锭,增加晶锭的有效利用长度,而且可以降低铸造多晶硅硅片的制造成本。
本工作利用微波光电导衰减仪(u-PCD)、红外扫描仪(SIRM)、二次离子质谱仪(SIMS)等测试方法对铸造多晶硅边皮料中的杂质以及少子寿命的分布特征进行了系统的研究。研究发现,SIMS测得硅锭中的氧浓度随硅锭高度的增加而逐渐降低,而碳的分布情形则刚好相反,随硅锭高度增大而增大。而且研究发现在边皮料的顶部阴影要比E13棒(硅锭中心棒)的阴影区长,少子寿命检测结果显示头尾红区都比E13长,这说明高浓度的杂质会降低铸造多晶硅材料的性能。所以边皮料再利用时,应把顶部和底部这些杂质较多的区域都去掉,然后再熔融利用。
关键词:铸造多晶硅,杂质,少子寿命,边皮料
The Investigation on Impurity Distribution in the
Edge of Casting Polycrystalline silicon
ABSTRACT
At present,in the production,casting polycrystalline silicon bubble is only 65%-70%,and another 30%-35% of casting polycrystalline silicon can not used for solar cells,this part of the casting polycrystalline silicon materials are the edge,head and tail because there are too much impurities in these density of impurities,play a crucial role on the degradation of mc-si solar cells the properties of these impurities and defects as well as their impacts on the quality of casting polycrystalline silicon materials could help us find the way to reduce the cost of mc-si solar cells .
In this thesis,the propreties of as-grown impurities and defects in casting polycrystalline silicon as well as their impacts on the minority carrier lifetime in mc-si ingots have been systematically studied by means of Microwavephoto Conductive Decay(μ-PCD),Scanning Infrared Microscopy(SIRM),and Secondary Ion Mass Spectroscopy(SIMS).The profiles of interstitial oxygen and substituted concentration were investigated by SIMS, the results show that the concentration of oxygen decreases form the bottom to the top of the ingot ,while in the case of carbon, just the opposite is true. The study also found that the shadow on the top of the edge materials is longer than E13 (silicon ingot center), and that minority carrier lifet