[tài yáng diàn chí]  

solar cell

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Solar cells, which are effectively absorbed solar energy And convert it into electric energy. Using semiconductors silicon selenium A device that converts the light energy of the sun into electrical energy. It has the advantages of high reliability, long life and high conversion efficiency Man made satellite A power supply for a radio, a transistor, etc. The size of single cell is from 1 × 1 cm to 15.6 × 15.6 cm, and the output power is tens of kilowatts to several watts. The theoretical photoelectric conversion efficiency is more than 25%, and the actual photoelectric conversion efficiency is more than 22%.
Chinese name
solar cell
Foreign name
solar cell
tài yáng diàn chí
Interpretation of meaning
It absorbs solar energy and converts it into electricity

solar cell Introduction to solar cell

Using semiconductor silicon Selenium and other materials will be the sun's Light energy become electric energy Device. It has the advantages of high reliability, long life and no pollution Man made satellite Beacon light Power supply for transistor radios, etc.
Solar cell is a kind of utilization Photovoltaic effect A device that converts light energy into electrical energy Photovoltaic devices , mainly including monocrystalline silicon Battery and single crystal Gallium arsenide Batteries, etc. The outer layer of the solar cell is made of pure silicon, such as silicon, silicon, etc., which is protected by the solar cell Radiation damage. The size of single cell is from 2 × 2 cm to 5.9 × 5.9 cm, and the output power is tens to hundreds of milliwatts. The theoretical photoelectric conversion efficiency is more than 20%, and the actual photoelectric conversion efficiency is more than 15%.
single crystal Gallium arsenide The theoretical photoelectric conversion efficiency of solar cells is 24%, and the actual photoelectric conversion efficiency is 18%. It can be used at high temperatures High light intensity However, the output of gallium is less and the cost is high. Cascaded p-n junction solar cell is a kind of p-n junction with different band gap materials superimposed on a substrate. The top junction with large band gap absorbs short wave light by the illumination surface, and the lower band gap decreases in turn. The absorbed light wave wavelength gradually increases. This kind of solar cell can make full use of sunlight and greatly improve the photoelectric conversion efficiency.
In order to improve the performance of single solar cells, we can take measures such as shallow junction, dense grid, back electric field, back reflection, texturing and multilayer film. Increasing the area of single cell is beneficial to reduce the energy consumption of solar cell array welding Point, improve reliability.

solar cell History of development

The development history of solar cells can be traced back to 1839, when Alexander Edmond Becquerel, a French physicist, discovered the photovoltaic effect. It was not until 1883 that the first selenium solar cell was made by American scientist Charles Fritts. In the 1930s, selenium batteries and Copper oxide Batteries have been used in some light sensitive instruments, such as photometers and exposure pins of cameras.
 The first solar cell in China The first solar cell in China
The modern silicon solar cells were not developed until 1946 by Russell OHL, a semiconductor researcher. Then in 1954, scientists increased the conversion efficiency of silicon solar cells to about 4%, and the next year to 11%. Later, solar cells were used in satellites.
After the energy crisis in 1973, human began to turn solar cells to civilian use. It was first used in calculators and watches. In 1974, haynos et al. Used the etching characteristics of silicon anisotropy to etch the textured surface with many pyramidal structures on the surface of single crystal silicon solar cells. The pyramid textured structure can effectively reduce the reflection loss of sunlight on the surface of the solar cell, making the conversion efficiency of the solar cell reach 17%.
After 1976, how to reduce the cost of solar cells has become the focus of the industry. After 1990, the reduction of battery cost made solar cells enter the field of private power generation, and solar cells began to be used in grid connected power generation.

solar cell classification

 classification classification
Classified solar cell is the core of photovoltaic power generation system. According to the maturity of production technology, solar cells can be divided into the following stages:
The first generation of solar cells: crystalline silicon cells;
Second generation solar cells: various thin film batteries. It includes amorphous silicon thin film cells (a-Si), cadmium telluride solar cells (CdTe), copper indium gallium selenium solar cells (CIGS), gallium arsenide solar cells Nano titanium dioxide Dye sensitized solar cells, etc;
The third generation of solar cells: a variety of stacked solar cells, thermal photovoltaic cells (TPV), quantum well and quantum dot superlattice solar cells, intermediate band solar cells, up conversion solar cells, down conversion solar cells, hot carrier solar cells, collision ionization solar cells and other new concept solar cells.
According to the cell structure, solar cells can be divided into crystalline silicon solar cells and thin film solar cells.
According to the basic materials used, solar cells can be divided into silicon solar cells, compound solar cells, dye-sensitized cells and organic thin-film cells.

solar cell Development

Silicon based solar cells
Silicon based batteries include polysilicon, monocrystalline silicon and amorphous silicon batteries. The efficiency of industrial crystalline silicon cells can reach 14% - 20% (single crystal silicon cells 16% - 20%, polycrystalline silicon 14% - 16%). At present, the proportion of polycrystalline silicon and monocrystalline silicon solar cells is nearly 90%. Silicon based batteries are widely used in grid connected power generation, off grid power generation and commercial applications.
(1) Solar cell [1]  
 Single crystal solar panel Single crystal solar panel
Among them, monocrystalline silicon solar cells have the highest conversion efficiency of 20% - 16%. At present, the technology of monocrystalline silicon doping and near grid passivation is widely used in cell surface.
The main ways to improve the conversion efficiency are surface microstructure treatment and zone doping process. In this regard, the Institute of solar energy system in Fraunhofer, Germany maintains the world leading level. The surface texture of the cell was fabricated by photolithography Inverted Pyramid A 13 nm thick oxide passivation layer was combined with two antireflective coatings on the surface. The ratio of width to height of the gate was increased by an improved electroplating process. The conversion efficiency of large area (225cm2) monocrystalline solar cells prepared by Kyocera company is 19.44%. The domestic Beijing Solar Energy Research Institute is also actively engaged in the research and development of high-efficiency crystalline silicon solar cells. The conversion efficiency of planar high-efficiency monocrystalline silicon cells (2cm × 2cm) reaches 19.79%, and the conversion efficiency of grooved buried gate electrode crystal silicon cells (5cm × 5cm) reaches 18.6%. The conversion efficiency of monocrystalline silicon solar cells is undoubtedly the highest, and it still occupies a dominant position in large-scale application and industrial production. However, due to the influence of the price of monocrystalline silicon materials and the corresponding cumbersome battery technology, the cost of monocrystalline silicon remains high.
(2) Polycrystalline silicon solar cell
At present, the main production cost of solar cells is low, and the main production efficiency is solar cells. Polycrystalline silicon solar cells have become the mainstream technology with the highest share of solar cells in the world. The efficiency of polysilicon solar cells is lower than that of monocrystalline silicon solar cells. It is close to the unit cost of power generation.
(3) Amorphous silicon solar cells
The advantage of amorphous silicon is that it has a strong absorption of visible spectrum (500 times stronger than that of crystalline silicon), so as long as a thin layer can effectively absorb the energy of photons. Moreover, this kind of amorphous silicon film production technology is very mature, which can not only save a lot of material costs, but also make it possible to make large area solar cells. The main disadvantage is that the conversion rate is low (5% - 7%), and there is photodecay (so-called S-W effect, that is, the photoelectric conversion efficiency will decay with the extension of illumination time, which makes the battery performance unstable). Therefore, it is not competitive in the small power market. Such as electronic calculators, toys, etc.
In the 1980s, amorphous silicon was the only commercial thin-film solar cell material. The appearance of amorphous silicon solar cell in that year caused a lot of investment. From 1985 to the beginning of 1990, the proportion of amorphous silicon solar cells reached one third of the total solar cells in the world. However, due to the poor stability, the output of amorphous silicon solar cells declined.
Thin film solar cell
According to different materials, thin film battery [2]   It can be subdivided into: thin film crystalline silicon solar cell (c-Si); thin film amorphous silicon solar cell Cell, referred to as a-Si), Ⅱ - Ⅵ compound solar cells (CdTe, indium copper selenide), Ⅲ - Ⅴ compound solar cells, such as gallium arsenide (GaAs), indium phosphide (INP), and indium gallium phosphide (InGaP). In addition to the Ⅲ - Ⅴ compound solar cells, the conversion efficiency of other concentrated thin film solar cells is generally less than 10%.
At present, there are three kinds of amorphous silicon solar cells, i.e., Indium Telluride (CIGS), amorphous silicon solar cells. In 2007, it accounted for 5.2% of global production.
(1) Ⅲ - Ⅴ solar cell compounds
The typical Ⅲ - Ⅴ compound solar cells are gallium arsenide (GaAs) cells with a conversion rate of more than 30%. This is because group Ⅲ - Ⅴ is a semiconductor material with direct energy gap, which can absorb about 97% of the light under the radiation condition of AM1 with only 2 um thickness. As a result of the high efficiency of the thin film deposited on the thin film of GaAs, it is applied in the solar cell by chemical deposition. The new generation of GaAs multi junction solar cells, due to their high absorption spectral range, can achieve conversion efficiency of more than 39%, which is currently the highest conversion efficiency of solar cells. Moreover, it has stable performance and long service life. However, this kind of battery is expensive, and the average price per watt is more than ten times higher than that of polysilicon solar cell, so it is not the mainstream of civil use.
Because of its direct energy gap, high absorption coefficient, good resistance to reflection damage and insensitive to temperature change, it is suitable for application in three main fields, such as thermovoltaics TRV, concentrator system and space.
Since August 2007, gallium arsenide (GaAs) batteries have shifted from satellite use to scale application of concentrating solar power stations. Gallium arsenide (GaAs) high-efficiency concentrator cells are being proved to be an effective way to build solar power plants with low cost in foreign countries.
(2) Ⅱ - Ⅵ compound solar cells
The Ⅱ - Ⅵ compound solar cells include CdTe thin film cells and Cu in GA se thin film batteries.
The direct energy gap of CdTe battery is 1.45ev, which is in the range of ideal solar cell. In addition, it has high absorption coefficient. High efficiency solar cells can be obtained as one of the ideal materials. In addition, in recent years, cdglass has been widely used in the production of various roof modules due to its good performance in commercial production. However, the development of thin-film batteries is a potential problem. However, the United States and Germany have implemented the recycling and regeneration mechanism of CdTe solar cells to inject positive force into the market. Because the battery production process takes only a few minutes and is easy to be produced in batch, the U.S. side is quite optimistic about the market prospect. It is considered that the occupation of amorphous silicon solar cells may exceed in the future.
The absorption range of Cu in GA se is very wide, and the stability is very good in outdoor environment. Because of its high conversion efficiency and low material manufacturing cost, it is regarded as one of the most potential thin film batteries in the future. In terms of conversion efficiency, with the help of concentrator, the conversion efficiency can reach about 30%, and the highest conversion efficiency can reach 19.5% under the standard environmental test, which is comparable to that of monocrystalline silicon solar cells. In addition to being suitable for large-scale surface applications, Cu (Inga) Se2 solar cells also have the ability to resist radiation damage, so they also have potential applications in the space field.
 Solar cells Solar cells
After 30 years of development, CIGS battery is still not popular. The small-scale mass production stage does not clearly see the cost advantage expected by the world. Therefore, how to make the mass production technology of solar cells mature and greatly reduce the manufacturing cost is the subject of future efforts. Another development direction is to develop CIGS technology with wide energy gap (more than 1.5ev) without causing efficiency loss. The development of low temperature manufacturing process which can produce high quality CIGS films is also a key point to reduce the manufacturing cost. Attracted by the market potential of low material cost and high die group efficiency, in recent years, in addition to shell solar, wrth solar, Showa shell, ZSW, etc., continue to invest in R & D, even Honda has followed up production. The hidden danger of CIGS solar cell development is that the reserves of in and GA are limited. Under the competitive use of other semiconductor and photoelectric industries, CIGS solar cells may face the same problem of insufficient silicon materials. At the same time, the complex manufacturing process and high investment cost restrict the market growth; CDs has the disadvantage of potential toxicity, which limits the market development.
Thin film solar cells on flexible substrates
Toledo University of the United States is a world leader in the research of amorphous silicon solar cells on flexible substrates. The initial efficiency of its single junction amorphous silicon germanium battery laboratory has reached 13%. Their technical team has participated in the establishment of mwoe and xunlight companies, and is actively planning for greater production capacity.
Japan is also at the forefront of research on flexible solar cells in the world. In Japan, sharp company, Sanyo company, TDK company and Fuji company have invested a lot of manpower and material resources in the research and development of amorphous silicon solar cells with flexible substrate, and have built several production lines of flexible polyester film solar cells of MW level.
Sanyo Amorphous solar cells were the first solar cells to fly across the continent. The amorphous silicon solar cells prepared by sharp company and TDK company on polyester film have been able to produce 286cm2 modules with an efficiency of 8.1% and a small area battery efficiency of 11.1%. Fuji's a-Si / a-sige stack cell has a stable efficiency of 9%. A factory has been set up in Kumamoto, Japan. The output of a-Si / a-sige solar cell on plastic substrate reached 15MW in 2006.
The European Union, together with a number of research institutions and organizations in its Member States, including Neuchatel University, VHF technologies, Roth & RAU, etc., has carried out joint research on flexible battery on polyester film substrate. At present, small batch production lines have been realized. On October 1, 2005, the European Union launched the "flexcellence" project, which lasted for three years. The goal is to develop high-efficiency roll to roll production equipment and process for thin-film battery modules, build a flexible battery production line with a capacity of more than 50 MW, and hope to control the production cost at 0.5 euro per watt. According to the current production capacity of nichtechnologies Co., Ltd., the capacity of amorphous polyester substrate reached 10.25 MW in 2007.
The research progress of flexible thin film battery in China is slow. In the mid-1990s, Harbin chrona company developed amorphous silicon single junction thin film battery on flexible polyimide substrate. The initial efficiency of the battery was 4.63%, and the power to weight ratio was 231.5w/kg. However, little progress has been made since then. In recent years, Nankai University has made some progress in the research of amorphous silicon thin film cells on flexible substrates. They obtained single junction thin film cells on 0.115cm2 polyimide substrate with an initial efficiency of 4.84% and a power to weight ratio of 341w / kg.
In terms of industrialization of flexible substrate battery, Tianjin Jinneng Battery Co., Ltd. is currently building a 6MW amorphous silicon flexible battery production line, and the 30MW production line has started project demonstration. Xinjiang Tianfu photovoltaic light display Co., Ltd. is building a 1MW amorphous silicon flexible battery production line, and is ready to build 8mW in the future. Due to the equipment and technology imported from abroad, the two companies expect high battery costs. Generally speaking, the domestic technology foundation for the development of amorphous silicon thin film battery is available, but the research on flexible substrate is still in its infancy, and there is a big gap between China and foreign countries. [3]  

solar cell Solar energy use

Solar power users
 Satellite solar panel Satellite solar panel
Solar cells
[1] The small power supply ranges from 10-100w, which is used for military and civilian life in remote areas without electricity, such as plateau, island, pastoral area, border guard post and so on, such as lighting, television, tape recorder, etc;
[2] 3-5kw household roof grid connected power generation system;
[3] Photovoltaic water pump: solve the problem of drinking and irrigation in deep water wells in areas without electricity.
2. Transportation
Such as beacon light, traffic / railway signal light, traffic warning / sign light, street lamp, high altitude obstacle light, highway / railway radio telephone booth, unattended road shift power supply, etc.
Satellite solar panel
 Solar street lamp Solar street lamp
3. Communication / communication field
Solar unattended microwave relay station, satellite, optical cable maintenance station, broadcast / communication / paging power system; rural carrier telephone Photovoltaic system Small communication machines, GPS power supply for soldiers, etc.
4. Petroleum, oceanography and meteorology
Solar power system for cathodic protection of oil pipeline and reservoir gate, domestic and emergency power supply for oil drilling platform, marine detection equipment, meteorological / hydrological observation equipment, etc
Solar street lamp
5. Household lamp power supply
Such as courtyard lamp, street lamp, portable lamp, camping lamp, mountaineering lamp, fishing lamp, black light lamp, tapping lamp, energy-saving lamp, etc.
 Solar cell clothing Solar cell clothing
. photovoltaic power station
10kw-50mw independent photovoltaic power station, wind (diesel) complementary power station, various large-scale parking charging stations, etc.
7. Clothing
Solar energy clothing, space suit, etc.

solar cell Latest development

The research team of the Institute of Polymer Optoelectronic Materials and devices, South China University of technology, on the basis of its initiative and independent intellectual property rights of water / alcohol soluble polymer solar cell interface control materials and technology, through collaborative innovation, using an inverted structure to achieve the energy conversion efficiency of 9.214% polymer solar cells, refreshing the energy of single junction polymer heterojunction solar cells The best level of quantity conversion efficiency in the world. This achievement was also recently selected as the "top ten scientific advances in China" in 2012.
This achievement was completed by the research team of Polymer Optoelectronic Materials and devices, which is composed of Professor Wu Hongbin, the winner of National Science Fund for Distinguished Young Scholars and Professor Cao Yong, academician of Chinese Academy of Sciences. They invented an efficient and novel inverted polymer solar cell with an energy conversion efficiency of 9.214%, which was independently certified by the national photovoltaic quality inspection center. The research results were published in the famous international academic journal "natural photonics", and were selected as research highlights by this issue. [4]  
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