Impact of thermal history of spherical silicon crystal on its crystal quality  

作　　者：TSUJIYA Kaoru MINEMOTO Takashi MUROZONO Mikio TAKAKURA Hideyuki HAMAKAWA Yoshihiro 

机构地区：[1]College of Science and Engineering, Ritsumeikan University 1-1-1 Nojihigashi, Kusatsu, Shiga 525-8577, Japan [2]Clean Venture 21 Co. Ltd., 35 Kamitoba Daimotsu-chou Minami-ku, Kyoto 601-8121, Japan

出　　处：《Rare Metals》2006年第z1期127-132,共6页稀有金属（英文版）

基　　金：This work was partly financially supported by NEDO.

摘　　要：Spherical Si solar cells were fabricated based on multicrystalline Si spheres produced by a dropping method. The thermal history of Si spheres were calculated by numerical simulation. The simulation result reveals that heat transfered by convection is greater than heat transfered by radiation. Considering the calculation results, Si spheres were dropped in the free-fall tower at low pressure state (0.2×105-0.5×105 Pa) to slow heat transfer by convection. After dash etching for 60 min, low pressure Si spheres have less etch pits, i.e., 80% for etch pit density and 8% for etch pit-area ratio compared to normal one. Furthermore, the conversion efficiency was improved from 6.57% (normal pressure spherical Si solar cell) to 9.56% (low one), which is 45% relative increase. The improvement is due to decrease of undercooling and increase of crystal growth duration. These results demonstrate that the dropping method at low pressure state is useful for fabricating high performance spherical Si solar cells.Spherical Si solar cells were fabricated based on multicrystalline Si spheres produced by a dropping method. The thermal history of Si spheres were calculated by numerical simulation. The simulation result reveals that heat transfered by convection is greater than heat transfered by radiation. Considering the calculation results, Si spheres were dropped in the free-fall tower at low pressure state (0.2×105-0.5×105 Pa) to slow heat transfer by convection. After dash etching for 60 min, low pressure Si spheres have less etch pits, i.e., 80% for etch pit density and 8% for etch pit-area ratio compared to normal one. Furthermore, the conversion efficiency was improved from 6.57% (normal pressure spherical Si solar cell) to 9.56% (low one), which is 45% relative increase. The improvement is due to decrease of undercooling and increase of crystal growth duration. These results demonstrate that the dropping method at low pressure state is useful for fabricating high performance spherical Si solar cells.

关 键 词：solar cell SPHERE silicon UNDERCOOLING low pressure thermal history etch pit 

分 类 号：TM914.41[电气工程—电力电子与电力传动]