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Solidification control of multicrystal silicon ingot for solar battery

太阳能电池用多晶硅锭的凝固控制

基本信息

批准号：
14350401
负责人：
OGI Keisaku
金额：
$ 6.66万
依托单位：
KYUSHU UNIVERSITY
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
2002
资助国家：
日本
起止时间：
2002 至 2004
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-14350401/
关键词：
Solar battery multicrystal silicon faceted growth twin boundary crystal growth undercooling photoelectric transformation diffusion length of carrier 発光電ファセット界面機能性材料ファセット

项目摘要

The mechanisms of columnar structure growth of the multicrystal silicon are investigated to the development of the photoelectric transformation efficiency and the productivity of solar battery cell fabricated by the unidirectional solidification technique.First of all, solar battery- grade high purity silicon crystals were solidified in small size crucibles (the inside diameter of 20 mm and the height of 100 mm) at the velocity of 0.075〜9.6 mm/s and a temperature gradient of 20K/cm by using the Bridgman type furnace. The undercoolings of nucleation and grain growth, the grain sizes and the crystal orientations of silicon multicrystal were investigated in related to the solidification conditions. The columnar structures are observed parallel to the heat flow direction in a velocity about 1 mm/min, and the larger size grains are obtained at the lower solidification speed. The crystal size becomes small with the increase of growth velocity and an equiaxed grain structure start forming abo … More ve a velocity around 1.8 mm/min.Twin boundaries, which have the crystal orientation relationship of sigma 3, grow parallel to the heat flow direction. Thus, the undercooling and driving force for crystal growth are estimated by the model based on two-dimensional nucleus growth regime. It was revealed that the undercooling of the <211> direction growth with twin boundary decreases to about 70 % of the case of <111> direction growth and reentrant corner of twin boundary gives an advantage to the faceted growth. Similar phenomena is obtained by the computer simulation based on the molecular dynamics theory. Therefore we conclude the kink site of the reentrant corner on twin boundary encourages the solidification velocity increasing and the development of grain size.The silicon crystal grows to the orientation between <211> to <101> along to the crucible bottom regardless on the form of the crucible shape and configuration at initial solidification stage. Similar phenomena are appeared even in the middle size specimen (the inside diameter of 80mm and the height of 20 mm) and also in the large size solar battery cell. Therefore, the grain size and grain orientation can be controlled by the covering the specimen bottom with the silicon crystal, which solidified toward the <211>〜<101> orientation due to the twin boundary at initial solidification stage, and then the growing upward at the relatively slow solidification velocity until final solidification stage. Less

为提高定向凝固太阳能电池的光电转换效率和生产率，研究了多晶硅的柱状结构生长机理。首先，利用布里奇曼式熔化炉在小尺寸的坩埚(内径20 mm，高度100 mm)中以0.075~9.6 mm/S的速度和20K/cm的温度梯度凝固了太阳能电池级高纯硅晶体。研究了多晶硅的形核过冷度、晶核长大过冷度、晶粒尺寸和晶体取向与凝固条件的关系。在1 mm/min左右的速度下，观察到平行于热流方向的柱状晶组织，较低的凝固速度可获得较大的晶粒尺寸。随着生长速度的提高，晶体尺寸变小，开始形成ABO…等轴晶组织。孪晶界沿热流方向平行生长，晶面取向关系为西格玛3。因此，基于二维晶核生长区域的模型估算了晶体生长的过冷度和生长驱动力。结果表明，孪晶界的&lt；211&gt；方向生长的过冷度降低到&lt；111&gt；方向生长的70%左右，孪晶界的折入角有利于多面生长。基于分子动力学理论的计算机模拟也得到了类似的现象。因此，我们得出结论：孪晶界上凹角的扭结位置促进了凝固速度的提高和晶粒度的长大。在初始凝固阶段，无论坩埚形状和构型如何，硅晶体都沿着&lt；211&gt；到&lt；101&gt；之间的取向生长。即使在中等尺寸的样品(内径80 mm，高度20 mm)和大尺寸的太阳电池中也出现了类似的现象。因此，可以通过在试件底部覆盖硅晶体来控制晶粒度和取向，在凝固初期，由于孪晶界的存在，硅晶会向&lt；211&gt；~&lt；101&gt；取向方向凝固，然后以相对较慢的凝固速度向上生长，直到最终凝固阶段。较少