Natural sunlight shines on the PN junction of the semiconductor device, giving rise to a new cavitation-electron pair. Under the action of the PN junction electric field, the cavitation is injected from the N zone into the P zone, and the electronic components are injected from the P zone into the N zone. After connecting the circuit, this results in the total flow of electricity. This is the working principle of photovoltaic effect solar cells. Solar power plants have two ways of generating electricity: one is light-heat-electricity conversion method, and the other is light-electricity conversion method.
(1) The light-heat-electricity conversion method is based on the power generation capacity of electric energy caused by the application of solar radiation intensity. Generally, the collector in the solar power station converts the digested electric energy into material vapor, and then controls the power generation capacity of the steam turbine. The former covers the whole process of light-heat conversion; the latter covers the whole process of heat-electricity conversion.
(2) The light-electricity conversion method is to use the photoelectric effect to convert the solar radiation intensity into electric energy immediately. The basic equipment of the light-electricity conversion is the solar cell. The solar cell is an electronic device that immediately converts sunlight energy into electrical energy due to the photo-generated ampere effect. It is a semiconductor device, photodiode. When natural sunlight hits the photodiode, the photodiode will convert natural light energy into electrical energy, resulting in the total flow of electricity. When many cells are connected in series or in cascade, it can become a solar cell drainage matrix with relatively large output power, and has excellent solar cell quality.
The regulations for polysilicon mainly come from semiconductor devices and solar cells. According to different requirements on purity, it is divided into electronic component level and solar power station level. Among them, polysilicon for electronic components accounts for about 55%, and polysilicon for solar power stations accounts for 45%.
With the rapid development of the photovoltaic industry, the demand for polysilicon for solar cells has grown faster than the development trend of polysilicon for semiconductor devices. It is expected that by 2008, the demand for polysilicon in solar power stations will exceed that of electronic components.
In 1995, the total value of solar cells in the world was only 69MW, but in 2004 it was close to 1200MW, which was an increase of 17 times in just ten years. It is predicted that the entire industrial chain of solar power generation will surpass chemical plants and becomes one of the most important basic energy sources in the first half of the 21st century.