According to the crystallization state, solar cells can be divided into crystalline thin film type and amorphous thin film type (hereinafter represented as A -), and the former is divided into single crystalline form and multi-crystalline form.
According to the materials, it can be divided into silicon thin film, compound semiconductor thin film and organic film, and compound semiconductor thin film can be divided into amorphous (A-Si: H, A-Si: H: F, A-Sixgel-X: H, etc.), ⅲ V group (GaAs, InP, etc.), ⅱ ⅵ group (Cds system) and zinc phosphating (Zn3p2), etc.
Solar cells according to different materials, the solar cell can also be divided into: silicon solar cells, multivariate compound thin film solar cells, polymer multilayer modified electrodes type solar cell, nanocrystalline solar cells, organic solar cells, including silicon solar battery is the most mature development, dominant in the application.
(1) Silicon solar cells
Silicon solar cells are divided into monocrystalline silicon solar cells, polycrystalline silicon thin film solar cells and amorphous silicon thin film solar cells.
Monocrystalline silicon solar cells have the highest conversion efficiency and the most mature technology. The highest conversion efficiency is 24.7% in the laboratory and 15% in scale production. It still occupies a dominant position in large-scale application and industrial production. However, due to the high cost of monocrystalline silicon, it is difficult to significantly reduce its cost. In order to save silicon materials, polycrystalline silicon film and amorphous silicon film have been developed as the alternative products of monocrystalline silicon solar cells.
Compared with monocrystalline silicon, polysilicon thin film solar cells have lower cost and higher efficiency than amorphous silicon thin film cells, with a maximum laboratory conversion efficiency of 18% and industrial scale conversion efficiency of 10%. Therefore, polysilicon thin film cells will soon dominate the market of solar power.
Amorphous silicon thin film solar cells have the advantages of low cost, light weight, high conversion efficiency, convenient mass production and great potential. However, due to the degradation effect of photoelectric efficiency caused by the material, its stability is not high, which directly affects its practical application. If the stability and conversion rate can be further solved, amorphous silicon solar cells will undoubtedly be one of the main development products of solar cells.
(2) Multi-compound thin film solar cells
The multicompound thin film solar cells are inorganic salts, including gallium arsenide III-V compound, cadmium sulfide, cadmium sulfide and coppers.
Cadmium sulfide and Cadmium telluride polycrystalline thin film cells have higher efficiency than amorphous silicon thin film solar cells, lower cost than monocrystalline silicon cells, and are also easy to mass production. However, because cadmium is highly toxic, it will cause serious pollution to the environment, so it is not the most ideal substitute for crystalline silicon solar cells.
The conversion efficiency of gallium arsenide (GaAs) III-V compound battery can reach 28%. GaAs compound material has very ideal optical band gap and high absorption efficiency, strong anti-irradiation ability, and is not sensitive to heat, so it is suitable for manufacturing efficient single-junction battery. However, the high cost of GaAs material limits the popularity of GaAs batteries to a large extent.
Copper-indium-selenium thin film cells (CIS) are suitable for photoelectric conversion without photodegradation and have the same conversion efficiency as polysilicon. The advantages of low price, good performance and simple technology will become an important direction for the development of solar cells in the future. The only problem is where the materials come from. Indium and selenium are both relatively rare elements, so the development of such batteries is bound to be limited.
(3) Polymer multilayer modified electrode type solar cells
Substituting organic polymers for inorganic materials is a nascent research direction in solar cell manufacturing. Due to the advantages of flexible organic materials, easy production, wide material sources, low cost and so on, it is of great significance to large-scale use of solar energy and provide cheap electric energy. However, the research on organic solar cells is just beginning, and neither the service life nor the efficiency of the cells can compare with inorganic materials, especially silicon cells. Whether it can be developed into practical products remains to be further studied and explored.
(4) Nanocrystalline solar cells
Nano TiO2 crystal chemical energy solar cells are recently developed, and their advantages lie in their low cost, simple process and stable performance. Its photoelectric efficiency is more than 10%, and its production cost is only 1/5 ~ 1/10 of that of silicon solar cells. The life span can reach more than 2O years.
However, as the research and development of such batteries is just starting, it is estimated that they will gradually go on the market in the near future.
(5) Organic solar cells
Organic solar cells, as the name implies, are solar cells with a core of organic materials. People are not familiar with organic solar cells, which is understandable. Today, more than 95 percent of mass-produced solar cells are silicon-based, while less than 5 percent are also made from other inorganic materials.