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Sun light in the semiconductor pn junction, a new hole - electron, in the pn junction of the electric field effect, by the hole n the flow of p zone areas, from e-p flow area n area, connected to the circuit after the current form. This is the photovoltaic solar cell works.

solar cell generate electricity in two ways, one is light - heat - electricity conversion methods, and the other is light - a direct electricity conversion methods.

1. Light - heat - electricity conversion methods through the use of solar radiation generated by thermal power generation, usually by solar collectors to  absorbed heat into the working fluid of steam, and steam turbine-driven power generation.First process is light- thermal conversion;

second is a process of heat - electricity conversion process.Ordinary, like power generation. Shortcomings of solar thermal power generation efficiency is very low and very high costs, it is estimated that at least its investment than ordinary fire Power 5 to 10 times more expensive. 1000MW of a solar thermal power plants need to invest 20 to 25 billion U.S. dollars, an average of 1kW for investment from 2000 to 2500 U.S. dollars.

As a result, only small-scale applied to special occasions, and the use of large-scale economically very uneconomical, and not compete with ordinary power plant or nuclear power plants .

2. Optical - directly into electricity by means of the use of photovoltaic, solar radiation will be directly converted to electrical energy. The basic power conversion devices is the solar cell. As the solar cell is a photovoltaic effect and convert solar energy directly into electrical energy. A semiconductor photodiode, when the sun's light to the photodiode, the photodiode will become the light of the sun electrical energy to produce current. When many batteries in series or parallel to be able to become more of the output power of the matrix solar cells. Solar cells is a promising new type of power, with a permanent, clean and flexibility of the three major advantages.The solar cell can be a long-term

investment, thermal power, nuclear power generation Compared to solar cells would not cause environmental pollution. solar cells can be both used in large to medium-sized 1,000,000 kilowatts of power, and also to a small use of solar energy battery,which is unmatched by other power.

The classification of solar cells

According to the state of crystalline solar cells can be divided into the Department of crystalline and amorphous thin-film-line (below that for a-) two major categories, while the former is further divided into single-and multi-crystal-shaped crystal.

By silicon thin film materials can be divided into shape, compound semiconductor thin film and organic-shaped membrane, and the compound semiconductor films are divided into non-crystalline form (a-Si: H, a-Si: H: F, a-SixGel-x: H, and so on), IIIV group (GaAs, InP, etc.), II VI group (Cds line) and zinc phosphide (Zn 3 p 2), and so on.

According to the solar cell by using different materials, the solar cells can be divided into: silicon solar cells, multiple compound film solar cells, multi-layer polymer-modified electrode solar cells, nano-crystalline solar cells of the four major categories.Silicon solar cells is the development of the most mature, the dominant applications.

Silicon solar cells

Silicon single crystal silicon solar cells into solar cells, polysilicon thin film solar cells and thin film amorphous silicon solar cells in three. Monocrystalline silicon solar cell conversion efficiency of the highest, most mature technology. In the laboratory of the highest conversion efficiency of 23%, the scale of production efficiency by 15%. In the large-scale application and industrial production is still dominant, but because of the high cost in single crystal silicon, a significant reduction in the cost is difficult, in order to save silicon materials, and the development of the polysilicon thin film amorphous silicon thin film as a single crystal Silicon solar cell alternative.

Polysilicon thin film silicon solar cells with relatively low cost, and more efficient than amorphous silicon thin film battery, the maximum conversion efficiency of the laboratory for 18% of the industrial-scale production of the conversion efficiency of 10%. As a result, polysilicon thin film solar cells will soon be in power to dominate the market.

Amorphous silicon thin film solar cells, light weight and low cost, high efficiency, ease of large-scale production, there is great potential.

However, the material caused by the photoelectric effect Efficiency recession, stability is not high, a direct impact on its practical application.

If you can solve problems and improve the stability of the conversion rate, then thin amorphous silicon cell is the main development of solar products.

Multi-film compound solar cells

Multi-film compound solar cells for inorganic materials, including gallium arsenide The main group III-V compounds, cadmium sulfide, cadmium sulfide copper and selenium stop film batteries. Cadmium sulfide, cadmium telluride polycrystalline thin film battery efficiency than that of amorphous silicon thin film solar cell efficiency, lower costs than single crystal silicon cells, as well as easy-to large-scale production, but because of a highly toxic cadmium, lead to serious environmental Pollution, crystalline silicon solar cells is not the best alternative.

Gallium arsenide (GaAs) III-V compounds cell conversion efficiency up to 28%, GaAs compound materials have very good optical band gap, as well as high efficiency of absorption, strong anti-radiation, heat insensitive, suitable for manufacturing High-performance single-junction cells. However, GaAs materials are not cheap, so to a large extent limited the use of universal GaAs cell.

Copper indium selenium thin film battery (the CIS) for photoelectric conversion, there is no photo-induced recession, the conversion efficiency of polycrystalline silicon and the same. With a low price, good performance and simple process, will be the future development of solar cells is an important direction. The only problem is that the source material, indium and selenium are due to the relatively rare element, type of battery

development will inevitably be limited.

Multi-layer polymer-modified electrode solar cell

Organic polymer in place of inorganic materials is just the beginning of a solar cell manufacturing research. As the organic material flexible, and easy to produce, the source of a wide range of materials, such as at the end of the cost advantages of large-scale use of solar energy in order to provide cheap power is of great significance. However, organic materials of the solar cell research is only the beginning, whether life or efficiency of the battery can not and inorganic materials especially compared to the silicon cells. Can be developed into practical products, yet to be explored further.

Nano-crystal Solar Cell

TiO2 nano-crystal solar cells chemical energy is a new development, the advantage of its cheap cost and simple process and the stability of performance. Photoelectric its efficiency and stability in more than 10%, making the cost of silicon solar cells is only 1 / 5 to 1 / 10. Life can reach more than 2O years. However, such battery research and development has just begun, it is estimated that in the near future will be gradually

stepped onto the market.