How are solar cells classified?
Solar cells, also known as photovoltaic cells, are devices that directly convert the energy of solar radiation into electrical energy.
This device is encapsulated in solar cell modules, and then a certain number of modules are combined into a solar cell array of a certain power according to the needs. Battery power generation system, also known as photovoltaic power generation system.
What do solar cells do?
Photovoltaic cells convert sunlight into electricity.
A photovoltaic (PV) cell, called a solar cell, is al device that converts sunlight directly into electricity. They can convert artificial light into electricity.
The basic device for photovoltaic solar energy generation is the solar cell.
The development history of solar cells has gone through a long development history of more than 160 years. From the overall development point of view, basic research and technological progress have played an active role in promoting, so far, the basic structure and mechanism of solar cells have not changed.
How do solar cells work in a simple way?
A solar cell is made up of two layers of silicon that are treated so that electricity flows through them when exposed to sunlight. First layer is positively charged and the second lyaer is negatively charged. When photons enter the layers, they give up their energy to the silicon atoms in the form of electrons.
Solar cells are classified by structure
- Homogeneous junction solar cells
- Heterogeneous junction solar cells
- Schottky solar cells
Solar cells are classified by material
- Silicon solar cells
- Multicomposite thin film solar cells
- Organic composite solar cells
- Sensitized nanocrystalline solar cells
- Polymer-modified multilayer electrode solar cells
- Classified solar cells (based on working)
- Flat panel solar cells
- Solar cell concentration
- Spectroscopic solar cells
The first generation: monocrystalline silicon and polycrystalline silicon, accounting for about 89.9% of the solar cell product market. The first generation of solar cells is based on silicon wafers, mainly using monocrystalline silicon and polycrystalline silicon as materials. Among them, the conversion efficiency of single-crystal silicon cells is the highest, which can reach 18-20%, but the production cost is high.
Second generation: thin film solar cells, accounting for 9.9% of the solar cell product market. Second generation solar cells are based on thin film technology and mainly use silicon and amorphous oxides as materials. The efficiency is lower than that of the first generation, the highest conversion efficiency is 13%, but the production cost is the lowest.
The third generation: composite thin-film solar cells such as copper indium selenide (CIS) and Si thin-film solar cells. Mainly in the laboratory production state, there are huge potential economic effects due to their high efficiency and low cost.
Silicon solar cells can be divided into:
1) Monocrystalline silicon solar cells
2) Polycrystalline silicon thin film solar cells
3) Amorphous silicon thin film solar cells
Monocrystalline silicon solar cells
Monocrystalline silicon solar cells are solar cells made of high-purity monocrystalline silicon rods, which have the highest conversion efficiency and the most mature technology.Their High-performance are based on high-quality silicon materials and related thermal processing techniques.
Amorphous silicon thin film solar cells
Its basic structure is not a pn junction but a pin junction. Doping boron to form the p region, doping phosphorus to form the n region, and is an intrinsic non-impure or lightly doped layer.
Featured features:
- Low cost of materials and manufacturing processes.
- The production process is a low temperature process (100-300℃) and the energy consumption is low.
- It is easy to form large-scale production capacity and the entire production process can be automated.
- There are many varieties and wide uses.
There are problems: optical band gap is 1.7 eV → insensitive to long wavelength region → low conversion efficiency
Photodegradation effect: photoelectric efficiency decreases with continued illumination time
Solution: Prepare tandem solar cells, i.e. deposit one or more pin subcells on the prepared single pin junction solar cells.
Production methods: reactive sputtering, PECVD, LPCVD.
Reactive gas: SiH4 diluted with H2
Substrate material: glass, stainless steel, etc.
Polycrystalline silicon solar cells
Polycrystalline silicon thin-film solar cells grow thin films of polycrystalline silicon on low-cost substrate materials and use a relatively thin layer of crystalline silicon as the active layer of solar cells, which not only maintains the high performance and stability of crystalline silicon solar cells, but also reduces the amount of materials used. A substantial drop, significantly reducing battery costs. The working principle of polycrystalline silicon thin-film solar cells is the same as other solar cells, which is based on the interaction of sunlight and semiconductor materials to form a photovoltaic effect.
Common preparation methods:
- Low pressure chemical vapor deposition (LPCVD)
- Plasma enhanced chemical vapor deposition (PECVD)
- Liquid phase epitaxy (LPPE)
- Powder deposition method
- Reactive gas SiH2Cl2, SiHCl3, SiCl4 or SiH4
↓ (under a certain protective atmosphere)
- Silicon atoms are deposited onto heated substrates
(The substrate material is Si, SiO2, Si3N4, etc.)
Problems: It is difficult to form larger grains on silicon-free substrates and it is easy to form voids between grains
Solution: First use LPCVD to deposit a thin layer of amorphous silicon on the substrate, then anneal this amorphous silicon layer to obtain larger crystal grains, and then deposit polysilicon film on the seed crystal.
Since polycrystalline silicon thin film cells use less silicon than monocrystalline silicon, there is no problem of efficiency . Therefore, polycrystalline silicon thin film cells will easily dominate the solar energy market.
Multicomposite thin film solar cells
Multi-compound thin-film solar cell materials are inorganic salts, mainly including group III-V compounds of gallium arsenide, cadmium sulfide, cadmium telluride, and copper indium selenide thin-film batteries.
The efficiency of multicomposite thin-solar cells is higher than that of amorphous silicon thin-film solar cells, and the cost is also lower than that of monocrystalline silicon cells, and it is also easy to mass produce, but because cadmium is highly toxic, it will cause serious damage to the environment. Pollution, so it is not the most ideal replacement for crystalline silicon solar cells.
The conversion efficiency of III-V gallium arsenide composite cells can reach 28%. Gallium arsenide composite material has a very ideal optical band and high absorption efficiency. It is insensitive to heat. It is suitable for the manufacture of high-efficiency single-junction batteries. However, the high price of gallium arsenide materials greatly limits the popularity of gallium arsenide batteries.
Copper indium selenide thin film battery (abbreviated as CIS) is suitable for photoelectric conversion and there is no problem of light-induced degradation effect, 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.
Organic composite solar cells
A type of solar cells that use carbon-based materials,to convert sunlight into electricity.
According to relevant survey data, the average cost of organic solar cells is only 10% to 20% of that of silicon solar cells; however, the photoelectric conversion efficiency of organic solar cells currently on the market is only 10% at most, which is the main problem limiting their comprehensive promotion. . Therefore, how to improve the photoelectric conversion rate is the key problem that should be solved in the future.
TYPES
Sensitized nanocrystalline solar cells
The dye-sensitized TiO2 solar cell is actually a photoelectrochemical cell. In 1991, a research group led by Professor Michael Grätzel at the Ecole Polytechnique de Lausanne (EPFL) in Switzerland used a low-cost, wide-bandgap oxide semiconductor TiO2 to prepare nanocrystalline thin films on which a large number of carboxylic acid-bipyridine Ru(II) complexes were adsorbed. A dye-sensitized nanocrystalline solar cell is developed using a low-volatile salt containing redox couples as the electrolyte.
The advantages of TiO2 nanocrystalline solar cells lie in their low cost, simple process and stable performance. Their photoelectric efficiency is stable at more than 10%, the production cost is only 1/5 to 1/10 of that of silicon solar cells, and their service life can reach more than 20 years. However, the research and development of these batteries has just begun, and it is estimated that they will gradually enter the market in the near future.
Fundamental:
The dye molecule absorbs the energy of sunlight and goes into the excited state, the excited state is unstable, the electrons are rapidly injected into the conduction band of the adjacent TiO2, and the electrons lost in the dye are quickly compensated by the electrolyte and the electrons entering. the conduction band of TiO2 finally enters. The conductive film then generates a photocurrent through the outer loop.
Polymer-modified multilayer electrode solar cells
Replacing inorganic materials with organic polymers is an emerging research direction for the manufacture of solar cells. Due to the advantages of good flexibility, easy fabrication, wide material sources and low cost of organic materials, it is of great significance for the large-scale utilization of solar energy and the provision of cheap electricity.
Research on the preparation of solar cells with organic materials has just begun, and neither the lifespan nor the efficiency of the cell can be compared with inorganic materials, especially silicon cells. It remains to be further studied and explored whether it can be developed into a product with practical significance.
Keheng solar energy storage battery
With technological progress and the cost advantages of lithium iron phosphate batteries becoming more and more obvious, current solar energy storage batteries are almost all lithium iron phosphate batteries.
Lithium iron phosphate batteries have the following advantages
- High safety performance
Long life:
The service life of long-life lead-acid batteries is about 300 times and the maximum is 500 times, while the service life of lithium iron phosphate batteries can reach more than 2,000 times, and the standard charge (5-hour charge) use can reach 2,000 times.
Good performance at high temperature
The peak electric heating of lithium iron phosphate can reach 350℃-500℃, while lithium manganate and lithium cobaltate are only around 200℃. Wide operating temperature range (-20C–75C), with high temperature resistance, the peak electric heating of lithium iron phosphate can reach 350℃-500℃, while lithium manganate and lithium cobaltate are only around 200℃.
- High energy density
- Light weight
- Environmental protection
Keheng solar energy storage battery is widely used in household energy storage and UPS telecommunications base station, portable outdoor power supply.
DEEP CYCLE BATTERIES With BMS (lithium lifepo4 battery)
60V 4AH low temperature deep cycle LiFePO24 battery
50V 4AH low temperature deep cycle LiFePO48 battery
100V 4AH low temperature deep cycle LiFePO48 battery
200V 4AH low temperature deep cycle LiFePO48 battery
200V 4ah low temperature deep cycle LiFePO12 battery
Low temperature heating enable 100AH 12V
About Us
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