| Project/Area Number |
14350401
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| Research Category |
Grant-in-Aid for Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Metal making engineering
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| Research Institution | KYUSHU UNIVERSITY |
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Principal Investigator |
OGI Keisaku KYUSHU UNIVERSITY, Faculty of Engineering, Professor, 大学院・工学研究院, 教授 (40038005)
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| Co-Investigator(Kenkyū-buntansha) |
MIYAHARA Hirofumi KYUSHU UNIVERSITY, Faculty of Engineering, Associate Professor, 大学院・工学研究院, 助教授 (90264069)
MORI Nobuyuki KYUSHU UNIVERSITY, Faculty of Engineering, Associate Professor, 大学院・工学研究院, 助教授 (20108666)
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| Project Period (FY) |
2002 – 2004
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| Project Status |
Completed (Fiscal Year 2004)
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| Budget Amount *help |
¥10,400,000 (Direct Cost: ¥10,400,000)
Fiscal Year 2004: ¥2,100,000 (Direct Cost: ¥2,100,000)
Fiscal Year 2003: ¥4,300,000 (Direct Cost: ¥4,300,000)
Fiscal Year 2002: ¥4,000,000 (Direct Cost: ¥4,000,000)
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| Keywords | 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 |
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| Research Abstract |
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
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