3. Solar Cells for SPS The cost of SPS solar cells is required to be of the same order as that of the terrestrialuse cell target in the Sunshine Project. However, the target performance of terrestrialuse solar cells is not always satisfactory for an SPS programme and it is necessary to improve their performance at many points. For example, SPS solar cells have to have as high a conversion efficiency as 17.5% at AMO and with lower degradation in the space environment, with phenomena such as particle irradiation. Besides lighter weight, superior strength in mechanical properties and compactness in the cargo are required. Table IV shows the expected performance of terrestrial-use solar cells at a production scale of 10 GW per year, that of SPS solar cells, and the additional improvements in the terrestrial use solar cell for SPS. Investigation of the Production Process We now follow the production process of a typical solar cell according to the flow chart in Fig. 4. Source Material Preparation Process (Si Halide, Polyciystalline Si). The process for synthesizing for metallurgical Si by reduction from silica is used widely in the steel and non-ferrous industry. Si Halide and Polycrystalline Si. Although the process for direct production of SOG Si is investigated, without the intermediate step of Si halide, it is not easy to abandon the process through Si halide, in view of the purity of silicon which is essential for obtaining a higher conversion efficiency. In the Japanese Sunshine Project, the NEDO
RkJQdWJsaXNoZXIy MTU5NjU0Mg==