At present, the mainstream product of solar cells-crystalline silicon solar cells has mature technology and stable performance, but currently does not have the market advantage to compete with conventional energy. The cost of the battery is mainly determined by the cost of raw materials, the scale of production, technology and management level. The cost issue is the bottleneck restricting the large-scale application of solar cells, and reducing the production cost is the main problem that must be solved in the direction of large-scale application. At present, the production cost of solar photovoltaic cells in China is on a downward trend. The price of solar cells has gradually dropped from 40 yuan/W in 2000 to 33 yuan/W in 2003, and has dropped to 27 yuan/W in 2004. It is necessary to make solar energy large-scale For industrialization, the power generation cost of solar cells must be close to the cost of conventional power generation methods, and must be reduced to less than 1 US dollar/peak watt (Wp) (1Wp=1W/㎡ solar intensity).
In terms of materials, the requirements for ideal solar cell materials are as follows: ①The band gap is between 1.1 and 1.7ev, close to 1.4ev to achieve the maximum photoelectric conversion efficiency; rich in resources, non-toxic and non-polluting; ③easy for mass production, Especially suitable for large-area, thin-film production; ④ high photovoltaic conversion efficiency; ⑤ long-term stability. Silicon has unique advantages in material selection
(1) Resource advantages of silicon materials
Solar cell products require high-purity raw materials. At present, the purity of silicon materials required for solar cells is 99.9998%, which is commonly referred to as 6 9s, which can also be expressed as 6N, and the purity required for semiconductor technology is several orders of magnitude higher. . The high-purity silicon material is prepared step by step with high-quality quartz sand as the raw material. Silicon is the most abundant element on the earth, accounting for the second place (25.8%), second only to oxygen, which accounts for the first place (49.5%). Silicon resources refer to crystals, vein quartz, quartz gravel (gravel-type quartz), natural silica sand, etc., which are non-metallic mineral deposits. The main chemical component is SiO2, which is abundant in nature. China has rich reserves of quartz and silica with high oxidation content and is widely distributed. High-grade silica-containing ore has been found almost all over the country, and the content of silicon dioxide is mostly above 99%. China is a large producer of quartz placer and has a large amount of mineral resources. China accounts for 1/3 of the world’s metallurgical silicon production. This is an extremely favorable resource condition for China to vigorously develop silicon solar cells.
(2) Performance advantages of silicon materials
The sensitivity of solar cells to light of different wavelengths is different, which is the spectral characteristic. The wavelength of the incident light corresponding to the peak of the spectral response is different. The wavelength of the silicon-based photovoltaic cell is around 0.8μm, and the spectral response wavelength range is 0.4~1.2μm. Compared with the solar cell of other materials, the silicon-based solar cell can be It is applied in a wide wavelength range. The crystalline silicon material is an indirect band gap material, and the width of the band gap (1.2eV) has a large difference with 1.4eV. From this point of view, silicon is not the most ideal solar cell material, but people have studied silicon materials the most. The processing technology is the most mature, stable and non-toxic. It is the main material for making semiconductor devices. The development of semiconductor devices depends on the development of information technology. The development of information technology and the photovoltaic industry jointly promotes the development of silicon material technology and production. develop. Although the cost of monocrystalline silicon solar cells is high, due to their stable performance, the highest photoelectric conversion efficiency, and the relatively mature technology, solar-grade monocrystalline silicon and cast polycrystalline silicon are still the most important material sources for solar cells in the world. Therefore, whether in terms of resources or technology, silicon solar cells have advantages that other materials cannot match.
From the perspective of photovoltaic industrial production in recent decades, monocrystalline silicon and polycrystalline silicon solar cells in silicon solar cells have become the main share of solar cell industrial production at this stage due to their abundant raw material resources and mature production techniques, accounting for more than 90%. In fact, the choice of materials for the semiconductor and photovoltaic industries has been discussed many years ago. From the perspective of the photovoltaic industry and semiconductor production in recent decades, the choice of silicon materials is correct.