Photovoltaic cells are devices that use the photovoltaic effect to detect optical radiation, mainly using valence band electrons to generate an electromotive force under illumination of light. Photocells are also called solar cells, which directly convert sunlight into electricity. Therefore, the photocell is characterized by the ability to convert a large amount of light energy absorbed by the earth from solar radiation into electrical energy.
There are many types of photocells, such as selenium photocells, silicon photocells, and antimony sulfide and silver sulfide photocells. Mainly used in instrumentation, automated telemetry and remote control. Some photovoltaic cells can directly convert solar energy into electrical energy, which is also called solar cells. Solar cells are widely used as energy sources in artificial satellites, lighthouses, unmanned weather stations, and the like.
With the implementation of sustainable development strategies around the world, the development and utilization of new energy is particularly important. The technology related to photovoltaic cells has entered our lives, so this research on the application and development direction of photovoltaic cells has a wide range of significance.
Type of photovoltaic battery
There are many types of photocells, such as selenium photocells, silicon photocells, and antimony sulfide, cadmium sulfide, and gallium arsenide photocells. Among them, silicon photocells are most widely used due to their high conversion efficiency, long life and low price.
Classification of photovoltaic cells
A. Single-layer Solar Cell:
The photocell is like a "sandwich". The outer two layers are the protective layer, and the middle layer is the main body, which is composed of silicon material.
The "Orbit electron" in the silicon atom is loose and easy to be "Bombard".
This is the same consideration as the "semiconductor (transistor)" made of silicon. Then there is "silicon" everywhere, cheap, and "physical" stable.
Light is shot continuously by the Sun from the "Photon".
In the white light, there are "component light" of "red, orange, yellow, green, blue, enamel, and purple". Today's commercial "photovoltaic cells" rely on "red light frequencies."
The surface of the photocell only allows "red light to pass" and reflects his color light.
"Red light Photon" releases the "Orbit Electron" from "矽", which is led to the converter (Inverter*) by a wire, and the direct current becomes alternating current (AlternaTIng Current). This kind of AC power can be used for "lighting", "hot water", "cooking", etc., just like the power supply of a power company.
* This is the equivalent of the "RecTIfier". The rectifier converts the alternating current into direct current.
Every "production" of electricity during the day is not enough, and it is sold back to the power company. No electricity in the evening, buy it from the power company! In this way, families with "photocells" on the roof pay only a limited monthly electricity bill. Home negative? Greatly relieved.
B. Multi-layer photocell (MulTI-layer Solar Cell):
The efficiency of using a single-cell photovoltaic cell is very low. The Mover sent to Mars on Mars used this MulTI-layer Solar Cell for more than three years and it still works.
Solar cells According to different materials used, solar cells can be divided into: silicon solar cells, multi-component thin film solar cells, polymer multilayer modified electrode solar cells, nanocrystalline solar cells, organic solar cells, among which silicon solar cells are currently The most mature development, leading in application。
(1) Silicon solar cells
Silicon solar cells are classified into three types: 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 in the laboratory is 24.7%, and the efficiency at scale is 15%. It still dominates in large-scale applications and industrial production. However, due to the high cost and cost of single crystal silicon, it is difficult to reduce its cost significantly. In order to save silicon materials, polycrystalline silicon thin films and amorphous silicon thin films have been developed as monocrystalline silicon solar energy. An alternative to the battery.
Compared with monocrystalline silicon, polycrystalline silicon thin film solar cells are cheaper and more efficient than amorphous silicon thin film cells. The highest conversion efficiency in the laboratory is 18%, and the conversion efficiency in industrial scale production is 10%. Therefore, polycrystalline silicon thin film batteries will soon dominate the solar power market.
Amorphous silicon thin film solar cells have low cost, light weight, high conversion efficiency, and are easy to mass-produce, and have great potential. However, due to the photovoltaic efficiency degradation effect caused by its material, the stability is not high, which directly affects its practical application. If it can further solve the stability problem and improve the conversion rate, then the amorphous silicon solar cell is undoubtedly one of the main development products of solar cells.
(2) Multi-component thin film solar cell
The multi-component thin film solar cell material is an inorganic salt, and mainly includes a gallium arsenide III-V compound, a cadmium sulfide, a cadmium sulfide, and a copper-bismuth selenide thin film battery.
The efficiency of cadmium sulfide and cadmium telluride polycrystalline thin film cells is higher than that of amorphous silicon thin film solar cells, the cost is lower than that of single crystal silicon cells, and it is also easy to mass produce. However, due to the high toxicity of cadmium, it will cause serious environmental damage. Pollution, therefore, is not the ideal replacement for crystalline silicon solar cells.
The conversion efficiency of gallium arsenide (GaAs) III-V compound battery can reach 28%. The GaAs compound material has ideal optical band gap and high absorption efficiency. It has strong anti-irradiation ability and is not sensitive to heat. It is suitable for manufacturing. High efficiency single junction battery. However, the price of GaAs materials is high, which limits the popularity of GaAs batteries to a large extent.
The copper indium selenide thin film battery (CIS for short) is suitable for photoelectric conversion, and there is no photo-induced degradation problem, and the conversion efficiency is the same as that of polysilicon. With the advantages of low price, good performance and simple process, it will become an important direction for the development of solar cells in the future. The only problem is the source of the material. Since both indium and selenium are relatively rare elements, the development of such batteries is bound to be limited.
(3) Polymer multilayer modified electrode type solar cell
The replacement of inorganic materials with organic polymers is just the beginning of a research direction in solar cell manufacturing. Due to the flexibility of organic materials, easy fabrication, wide source of materials, and low cost, it is of great significance for the large-scale use of solar energy to provide cheap electrical energy. However, research on the preparation of solar cells from organic materials has only just begun, and neither the service life nor the battery efficiency can be compared with inorganic materials, especially silicon batteries. Whether it can be developed into a product of practical significance remains to be further explored.
(4) Nanocrystalline solar cells
Nano-TiO2 crystal chemical energy solar cells are newly developed, with the advantages of low cost, simple process and stable performance. Its photoelectric efficiency is stable at more than 10%, and the production cost is only 1/5 to 1/10 of the silicon solar cell. Life expectancy can reach more than 20 years.
However, due to the research and development of such batteries, it is estimated that they will gradually enter the market in the near future.
(5) Organic solar cells
Organic solar cells, as the name suggests, are solar cells that are made up of organic materials. Everyone is unfamiliar with organic solar cells, which is a reasonable thing. More than 95% of today's mass-produced solar cells are silicon-based, while less than 5% of the rest are made from other inorganic materials.