Energy, economy and environment are considered as the three main problems of men's continuous development. The shortage of the energy and the deterioration of environment restrict the growing of economy. Solar energy will soon be in great demand since it is inexhaustible and much cleaner than any other conventional energy resources. The photovoltaic industry is growing at the rate of 30% annually. In the near future, the photovoltaic industry will face a severe shortage of crystalline silicon, because the o...