Thursday, May 27, 2010

More Powerful Flexible GaAs Solar Cells Developed by National Chiao Tung University Researchers

National Chiao Tung University (Hsinchu, TW) researchers Edward Yi Chang, Shih-Hsuan Tang and Yue-Cin Lin developed  a way to make solar cells that does not use the germanium substrate of conventional solar cell technology but the GaAs is deposited on the silicon substrate to form the solar cell instead.

The ion implantation method is used to reduce the stress between the silicon wafer and the SiGe epitaxial layer. Then the SiGe buffer layer is grown on the silicon substrate. Furthermore, the Ge thin layer is grown on the SiGe buffer layer, and the solar cell structure is grown on the Ge layer. The process is disclosed in U.S. Patent Application 20100129956.

The invention can lighten the weight of the solar cell. The invention can be grown on larger silicon wafer (above six inches), which can reduce the cost greatly.

The method uses the Si+ implanted Si substrate to enhance the strain relaxation at the interface between the Si substrate and the SiGe epitaxial layer.

The researchers grew the SiGe buffer layer on the Si substrate, and use the generated stress field between the interface to block the formation and penetration of dislocations, in order to reduce the dislocation density of the SiGe epitaxial layer.

The invention uses the Si substrate as the substrate of III-V solar cell, which can raise the mechanical property of the solar energy chip effectively, in order to reduce the manufacturing cost and lighten the weight of the solar cell.

The invention can raise the light concentration folds of the solar cell, adjust the interface of different materials, and raise the conversion efficiency.

The technique can make the flexible solar cell, the main characteristics are the followings: Tt can be used as energy gap material directly, it can absorb sunlight effectively. The conversion efficiency of multiple-junction solar cell is up to 39%. It can still maintain good operation feature at the environment of high temperature. It is suitable to be used under the light concentration condition.  The solar cell chip can obtain high-efficiency and full-spectrum absorption effect through using texture, quantum well, and multiple-junction epitaxial structure.

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