The working principle and classification of solar cells

Date:Apr 17, 2019

How photovoltaic power to work.

Photovoltaic power generation is a technology that directly converts light energy into electrical energy by utilizing the photovoltaic effect of the semiconductor interface. The key component of this technology is the solar cell. The solar cells are packaged and protected in series to form a large-area solar cell module, and then combined with a power controller and the like to form a photovoltaic power generation device. The advantage of photovoltaic power generation is that it is less restricted by geographical area, because the sun shines on the earth; the photovoltaic system also has the advantages of safe and reliable, no noise, low pollution, no need to consume fuel and erecting transmission lines to generate electricity on site and short construction period.

Photovoltaic power generation uses solar cells to convert solar energy directly into electrical energy based on the principle of photovoltaic effect. Whether it is independent use or grid-connected power generation, photovoltaic power generation system is mainly composed of three parts: solar panels (components), controllers and inverters. They are mainly composed of electronic components and do not involve mechanical components. Therefore, photovoltaic power generation equipment Extremely refined, reliable, stable, long life, easy installation and maintenance. In theory, photovoltaic power generation technology can be used in any occasion where power is required, from spacecraft to household power supplies, to megawatt power stations, to toys, and photovoltaic power sources everywhere. The most basic components of solar photovoltaic power generation are solar cells (sheets), such as monocrystalline silicon, polycrystalline silicon, amorphous silicon and thin film batteries. At present, single crystal and polycrystalline batteries are used the most, and amorphous batteries are used for some small systems and calculator auxiliary power supplies.

The efficiency of domestic crystalline silicon cells is about 10 to 13%, and the efficiency of similar foreign products is about 18 to 23%. A solar panel composed of one or more solar cells is referred to as a photovoltaic module. At present, photovoltaic power generation products are mainly used in three aspects: First, to provide power for non-electrical occasions, mainly to provide electricity for the living production of residents in the vast areas without electricity, microwave relay power, communication power, etc. In addition, some mobile Power supply and backup power; Second, solar energy daily electronic products, such as various types of solar chargers, solar street lights and solar lawn lights; third, grid-connected power generation, which has been widely implemented in developed countries. China's grid-connected power generation has not yet started, but some of the electricity used in the 2008 Beijing Olympic Games will be provided by solar power and wind power.

Type of solar cell

(1) Monocrystalline silicon solar cells

The photoelectric conversion efficiency of monocrystalline silicon solar cells is about 15%, and the highest is 24%. This is the highest photoelectric conversion efficiency among all kinds of solar cells, but the production cost is so large that it cannot be widely used. Commonly used. Since monocrystalline silicon is generally encapsulated with tempered glass and waterproof resin, it is durable and has a service life of up to 15 years and up to 25 years.

(2) Polycrystalline silicon solar cells

The manufacturing process of polycrystalline silicon solar cells is similar to that of monocrystalline silicon solar cells, but the photoelectric conversion efficiency of polycrystalline silicon solar cells is much lower, and its photoelectric conversion efficiency is about 12% (July 1, 2004, Japan's Sharp listing efficiency is 14.8%. The world's most efficient polysilicon solar cell). In terms of production cost, it is cheaper than monocrystalline silicon solar cells, the material is simple to manufacture, saves power consumption, and the total production cost is low, so it has been greatly developed. In addition, the life of polycrystalline silicon solar cells is also shorter than that of monocrystalline silicon solar cells. In terms of performance and price ratio, monocrystalline silicon solar cells are slightly better.

(3) Amorphous silicon solar cells

Amorphous silicon solar cells are new thin film solar cells that appeared in 1976. They are completely different from single crystal silicon and polycrystalline silicon solar cells. The process is greatly simplified, the silicon material consumption is small, and the power consumption is lower. The advantage is that it can generate electricity in low light conditions. However, the main problem of amorphous silicon solar cells is that the photoelectric conversion efficiency is low. At present, the international advanced level is about 10%, and it is not stable enough. As time goes by, its conversion efficiency is attenuated.

(4) Multi-component solar cells

A multi-component solar cell refers to a solar cell that is not made of a single element semiconductor material. Nowadays, there are many varieties of research in various countries, most of which have not been industrialized, mainly including the following: a) cadmium sulfide solar cells b) gallium arsenide solar cells c) copper indium selenide solar cells (new multi-band gap gradient Cu (In, Ga) )Se2 thin film solar cell)

Cu(In, Ga)Se2 is a kind of solar absorbing material with excellent performance. It has a multi-layer semiconductor material with gradient energy band gap (the energy level difference between conduction band and valence band), which can expand the solar absorption spectrum range and improve photoelectric conversion. effectiveness. Based on this, a thin film solar cell with a significantly higher photoelectric conversion efficiency than a silicon thin film solar cell can be designed. The photoelectric conversion rate that can be achieved is 18%. Moreover, such thin film solar cells have not been found to have a performance degradation effect (SWE) due to optical radiation, and the photoelectric conversion efficiency thereof is improved by about 50~ compared with the currently commercial thin film solar panels. 75% is the world's highest level of photoelectric conversion efficiency in thin film solar cells.

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