Fig. 1. Cost prospect for solar cells in near future (DOE). On the other hand, for the purpose of improving mass producibility, several cast Si technologies have been attempted. Among them, the heat exchange method to obtain large grain size polycrystal and spin method of molten Si (5) are quite unique. Amorphous Si Solar Cell Technology The amorphous Si solar cell is expected for the future photovoltaic power source because of its potential excellence at the point of low consumption of resource and high producibility. The amorphous Si solar cell requires only 0.5-1.0 /rm in thickness because of its considerably high absorption coefficient of light. It is made by plasma CVD method, which is widely used in semiconductor industry, using silane gas. The main items for development are an increase of conversion efficiency, an improvement of reliability and the pursuit of high speed deposition technology. Tandem structure solar cell development, doping of fluorine and disilane CVD technology are now in development. The value of conversion efficiency increases markedly year by year as shown in Fig. 2. Recent reports show the efficiency more than 10% for small area solar cell (13). PROSPECT FOR THE GROWTH OF PHOTOVOLTAIC INDUSTRY In Japan, 3-4 MWp of solar cell has been thought to be manufactured in fiscal year 1983. Among these, the entertainment use of solar cells such as for electronic handy calculator-use occupies the main part, which is a marked feature of the Japanese
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