Overview of Solar-Silicon Thin Film Solar Cells

Definition of silicon based thin film solar cell

According to the report released by nano markets on March 30, 2009, amorphous silicon (a Si) thin film photovoltaic materials will continue to lead the development of thin film photovoltaic materials in the next few years since they appeared in the late 1970s.

(1) Preparation technology of polysilicon film

Preparation technology of polysilicon film
Preparation technology of polysilicon film

Polycrystalline silicon thin film material has the advantages of high mobility of monocrystalline silicon material and large area and low cost preparation of amorphous silicon material. Therefore, the research on polysilicon thin film materials has attracted more and more attention. The preparation process of polysilicon thin film can be divided into two categories: one is high-temperature process, the temperature in the preparation process is higher than 600 ℃, the substrate uses expensive quartz, but the preparation process is relatively simple; The other is the low-temperature process. The temperature of the whole processing process is lower than 600 ℃, and cheap glass can be used as the bottom of the village, so it can be made in a large area. However, the preparation process is complex. At present, there are mainly the following methods to prepare polysilicon films. (1) Low pressure chemical vapor deposition.

Low pressure chemical vapor deposition (LPCVD) is a direct method to produce polycrystalline silicon LPCVD is a standard method commonly used in the preparation of polycrystalline silicon films used in integrated circuits. It has the characteristics of fast growth rate, dense and uniform film formation and large loading capacity. Polycrystalline silicon films can be deposited directly on the substrate by LPCVD method with silane gas. The typical deposition parameters are silane pressure of 13.3-26.6pa, deposition temperature T d = 580 ~ 630 ℃, growth rate of 5 ~ 10nm / min, If the softening temperature of ordinary glass is 500 ~ 600 ℃, cheap ordinary glass cannot be used, but expensive quartz must be used as the substrate.

The polycrystalline silicon films grown by LPCVD have preferred grain orientation, V-shaped morphology, high-density micro contracture defects, small grain size and insufficient carrier mobility, which limit their application in devices. Although reducing silane pressure helps to increase the grain size, it is often accompanied by the increase of surface roughness, which has an adverse impact on the mobility of carriers and the electrical stability of devices.

(2) Solid phase crystallization.

The so-called solid phase crystallization (SPC) refers to that the crystallization temperature of amorphous solids is lower than the crystallization temperature after melting. This is a method of indirectly generating polycrystalline silicon. Firstly, silicon burning gas is used as raw material, and a-Si: H film is deposited at about 550 ℃ by LPCVD method. Then the film is melted at a high temperature above 600 ℃, and then the crystal nucleus appears at a slightly lower temperature. With the decrease of temperature, the molten silicon continues to crystallize on the crystal nucleus to increase the grain size and convert into polycrystalline silicon film. When using this method, the grain size of polysilicon film depends on the thickness and crystallization temperature of the film.

Annealing temperature is an important factor affecting the crystallization effect. In the annealing temperature range below 700 ℃, the lower the temperature is, the lower the nucleation rate is, and the larger the grain size can be obtained when the annealing time is the same; Above 700 ℃, the grain size increases with the increase of temperature due to the mutual annexation of grains caused by the movement of grain boundaries. A large number of studies show that the grain size of polycrystalline silicon prepared by this method is also closely related to the disorder degree of the initial thin film samples. Aoyama et al. Studied the influence of the deposition conditions of the initial material on the solid-phase crystallization, and found that the more disordered the initial material, the lower the nucleation rate and the larger the grain size during the solid-phase crystallization process. Because the formation of crystal nucleus is spontaneous in the crystallization process, the crystal plane orientation of SPC polycrystalline silicon film is random. Different orientations of adjacent grain planes will form a higher potential barrier, and hydrogenation treatment is needed to improve the performance of SPC polysilicon. The advantage of this technology is that it can prepare large-area thin films, and the grain size is larger than that of polycrystalline silicon deposited directly. It can be doped in situ, with low cost, simple process and easy to form a production line. Since SPC crystallizes at the melting temperature of amorphous silicon, it belongs to a high-temperature crystallization process. When the temperature is higher than 600 ℃, it usually takes about 1100 ℃ and the annealing time is more than 10 hours. It is not suitable for glass substrate. The substrate material is quartz or monocrystalline silicon, which is used to make small-size devices, such as liquid crystal light valve, camera viewfinder, etc.

(3) Excimer laser crystallization

Laser crystallization (ELA) is more ideal than solid-state crystallization to prepare polycrystalline silicon. It uses the high energy generated by instantaneous laser pulse to incident on the surface of amorphous silicon film, and only produces thermal energy effect at the depth of 100nm on the surface of the film, so that the instantaneous temperature of a-Si film can reach about 1000 ℃, so as to realize the transformation from a-Si to p-Si. In this process, the instantaneous (15 ~ 50ns) energy of the laser pulse is absorbed by the a-Si film and converted into phase change energy. Therefore, too much heat energy will not be transmitted to the film substrate. Reasonably select the wavelength and power of the laser, and use the laser heating to make the a-Si film reach the melting temperature and ensure that the substrate temperature is lower than 450 ℃. The glass substrate can be used as the substrate, which realizes the preparation of p-Si film, It can also meet the requirements of LCD and OEL for transparent substrate. Its main advantages are short pulse width (15 ~ 50ns) and low substrate heating. Through selection, mixed crystallization can be obtained, that is, the mixture of polycrystalline silicon and amorphous silicon. The mechanism of excimer laser annealing crystallization is that the laser radiates to the surface of a-Si, so that the surface reaches the crystallization domain value when the temperature reaches the melting point. The energy density e. a Si absorbs energy under laser radiation, excites the unbalanced electron hole pair, and increases the conductive energy of free electrons. The hot electron hole pair transmits its energy to the lattice by means of non radiation recombination during the heating time, resulting in extremely rapid temperature rise in the near surface layer. Because amorphous silicon materials have a large number of dry states and deep energy levels, non radiative transition is the main recombination process, so it has high photothermal conversion efficiency. If the energy density of the laser reaches the city value energy density e, that is, when the semiconductor is heated to the melting point temperature, the surface of the film will melt, and the melting front will go deep into the interior of the material at the speed of about 10m / s. after laser irradiation, the film forms a certain depth of melting layer. After stopping the irradiation, the melting layer begins to cool at the speed of 108 ~ 1010k / s.

The interface between solid phase and liquid phase will return to the surface at the speed of 1-2m / s. after cooling, the film crystallizes into polycrystalline. With the increase of laser energy density, the grain size increases. When the amorphous film is completely melted, the film will crystallize into microcrystals or multiple products. If the laser energy density is less than the domain energy density e, that is, the absorbed energy is not enough to raise the surface temperature to the melting point, the film will not crystallize. Generally, when the energy density increases, the grain size increases, and the mobility of the film increases accordingly. When the Si film is nearly completely melted, the particle size is the largest, but the energy is limited by the laser and cannot increase indefinitely. Too large energy density will reduce the mobility. The longer the wavelength is, the deeper the laser energy is injected into the Si film, the better the crystallization effect is The polycrystalline silicon film prepared by ELA method has large grain size, good spatial selectivity, high doping efficiency, few intracrystalline defects, good electrical properties and high mobility, up to 400cm2 / (v.s). It is the low-temperature polycrystalline silicon film with the best comprehensive performance at present. Elvi has high maturity and large production line equipment, but it also has its own shortcomings. The grain size is sensitive to laser power, poor large-area uniformity, poor repeatability, high equipment cost and complex maintenance.

(4) Rapid thermal annealing (RTA)

Generally speaking, the rapid annealing process includes three stages: heating stage, stabilization stage and cooling stage. As soon as the power supply of the annealing furnace is turned on, the temperature rises with time. This stage is called the heating stage. The change of temperature per unit time is easy to control. At the end of the heating process, the temperature is in a stable stage. Finally, when the power supply of the annealing furnace is turned off, the temperature decreases with time. This stage is called the cooling stage. Amorphous silicon containing hydrogen is used as the initial material for annealing. When the equilibrium temperature is controlled above 600 ℃, nano silicon grains can be formed in amorphous silicon films, and the size of nano silicon grains changes with the temperature rise during annealing. In the heating process, if the temperature change per unit time is large (such as 100 ℃ / s), the nano silicon grains formed are small (1.6 ~ 15nm); If the temperature change per unit time is small (e.g. 1 ℃ / s), the nano silicon particles are large (23-46 nm). Further experiments show that prolonging the annealing time and increasing the annealing temperature can not change the size of the formed nano silicon particles; During annealing, the speed of temperature rise directly affects the grain size of nano silicon. In order to find out the influence of heating rate on the size of nano silicon grains, the nucleation theory in crystal growth was adopted. There are two steps in crystal growth. The first step is nucleation and the second step is growth. In other words, in the first step, a sufficient amount of growth products is required. The results show that the rate of temperature rise affects the density of fine grains. If the temperature change per unit time is large, the density of fine grains will be large; On the contrary, if the temperature change per unit time is small, the resulting product density is small. Increasing the annealing temperature or prolonging the annealing time during RTA annealing can not eliminate the non product part in the film. From bottom to top, as long as the temperature is not too high so that the adjacent Nalesi islands do not melt, even increasing the annealing temperature or prolonging the annealing time can not completely eliminate the amorphous part.

The polycrystalline silicon prepared by RTA annealing method has small grain size, large grain boundary density in the crystal and high material defect density. Moreover, it belongs to high-temperature annealing method, which is not suitable for preparing polycrystalline silicon with glass as substrate.

(5) Plasma enhanced chemical reaction vapor deposition.

Plasma enhanced chemical reaction vapor deposition.
Plasma enhanced chemical reaction vapor deposition.

Plasma enhanced chemical skinning vapor deposition (PECVD) uses the electrons of glow discharge to activate the chemical vapor deposition reaction. At first, the gas was inevitably slightly ionized due to the radiation of high-energy cosmic rays such as ultraviolet rays, and there were a small number of electrons. The excitation source (such as DC high voltage, RF, pulse power supply, etc.) is introduced into the reaction vessel filled with rare gas. The electron obtains energy under the acceleration of the electric field. When it collides inelastic with the neutral particles in the gas, it may produce secondary electrons. If it collides and ionizes repeatedly, a large number of ions and electrons will be produced. Because the number of positive and negative particles is equal, it is called plasma, And release excess energy in the form of luminescence, that is, form “glow”. In the plasma, due to the great difference in the mass of electrons and ions, the process of energy exchange between them through collision is relatively slow, so all kinds of charged particles in the plasma reach their thermodynamic equilibrium. Therefore, there will be no unified temperature in such a plasma, only the so-called electron temperature and ion temperature. At this time, the temperature of electrons can reach 104 ℃, while the temperature of molecules, atoms and ions is only 25-300 ℃. Therefore, from a macro point of view, the temperature of this plasma is not high, but its internal electrons are in a high-energy state and have high chemical activity. If the excited energy exceeds the thermal energy required for chemical reaction, the excited electron energy (1 ~ 10ev) is enough to open the molecular bond, resulting in the production of chemically active substances.

Therefore, the chemical reaction originally required to be carried out at high temperature can occur at low temperature and even at room temperature through the action of discharge plasma. The process of PECVD film deposition can be summarized into three stages:

·SiH4 decomposes to produce active particles Si, h, sih2 and sih3.

·Adsorption and diffusion of active particles on the substrate surface.

·The active molecules adsorbed on the village bottom react on the surface to form a poly Si layer and release H2. In the process of plasma assisted deposition, the bombardment of ions and charged groups on the deposited surface is one of the important factors affecting the crystallization quality. This effect can be overcome by external bias. There are two main viewpoints on the crystallization process of polycrystalline silicon films prepared by PECVD Technology: one is that the active particles are first adsorbed to the substrate surface, and then various surface processes such as migration, reaction and dissociation occur, so as to form the crystalline phase structure. Therefore, the surface state of the substrate plays a very important role in the crystallization of the films; The other is that the space gas phase reaction plays a more important role in the low-temperature crystallization of the film, that is, the particles with crystal phase structure are first formed in the space plasma region, and then diffuse to the substrate surface to grow into polycrystalline film. For SiH4: H2 gas system, some studies show that under the condition of high hydrogen doping, when depositing polycrystalline silicon films by rfpecvd, the substrate must be heated to more than 600 ℃ in order to promote the formation of crystal nuclei in the initial growth stage. When the substrate temperature is less than 300 ℃, only hydrogenated amorphous silicon (a-Si: H) films can be formed. Using SiH4: H2 as the gas source to deposit polycrystalline silicon has a high temperature, generally higher than 600 ℃, which is a high-temperature process and is not suitable for glass substrate. At present, it is reported that polycrystalline silicon can be obtained by depositing polycrystalline silicon with SiCl4: H or SiF4: h as the gas source at a low temperature. However, polycrystalline silicon prepared by CVD has small grain size, generally no more than 50mm, many intragranular defects and many grain boundaries.

(6) Metal transverse induction method (MILC)

In the early 1990s, it was found that adding some metals into a-Si, such as Al, Cu, Au, Ag and Ni, deposited on a-Si: H or ion implanted into a-Si: H film, can reduce the phase transition energy of a-Si to p-Si, and then annealing Ni / a-Si: H to crystallize a-Si film, and the crystallization temperature can be lower than 500 ℃. However, due to metal pollution, it can not be used in TFT. Subsequently, it was found that the transverse induced crystallization of Ni could avoid the formation of contracture. The lattice constant of Ni Si compound was similar to that of monocrystalline silicon, and had low mutual solubility and appropriate phase transition energy. The transverse crystalline polycrystalline silicon film was obtained by the method of nickel induced a-Si film. The surface of transversely crystallized polycrystalline silicon film is smooth, with the characteristics of long grain and continuous grain boundary. The grain boundary barrier height is lower than that of SPC polycrystalline silicon. Therefore, MILC TFT has excellent performance and does not need to be hydrogenated. The metal (such as nickel) is used to form an induction layer on the surface of amorphous silicon film, and the metal Ni and a Si form Ni Si silicide at the interface. Using the latent heat released by silicide and the character position provided by lattice error at the interface, a-Si atoms recrystallize at the interface to form polycrystalline silicon grains. Ni Si layer is destroyed, and Ni atoms gradually migrate to the bottom layer of a-Si layer to form Ni Si and silicide, This is repeated until the a Si layer is basically crystallized. The induction temperature is generally 500 ℃, and the duration is 10h. The annealing time is related to the film thickness.

Polycrystalline silicon films prepared by metal induced amorphous silicon crystallization method have the advantages of high uniformity, low cost, amorphous silicon outside the connected metal masking area can also be crystallized, and the growth temperature is 500 ℃. However, the current crystallization rate of MILC is still not high, and the rate will decrease with the increase of heat treatment time. We use the combination of MILC and optical pulse radiation to realize the rapid transverse crystallization of a Si film at low temperature, and obtain polycrystalline silicon belt with high mobility and low metal pollution.

In addition to the above main methods for preparing polycrystalline silicon films, there are also ultra-high vacuum chemical vapor deposition (UHV / CVD), electron beam evaporation and other methods. Polycrystalline silicon can be grown by UHV / CVD. When the growth temperature is lower than 550 ℃, high-quality fine-grained polycrystalline silicon thin film can be generated without recrystallization, which can not be done by traditional CVD. Therefore, this method is very suitable for the preparation of low-temperature polycrystalline silicon thin film transistors. In addition, Hitachi research points out that polysilicon can also be realized by electron beam evaporation, and the temperature is lower than 530 ℃. Therefore, we believe that with the increasing maturity of the above polysilicon preparation methods and the emergence of new preparation methods, the development of polysilicon technology will reach a new level, so as to promote the development of the whole semiconductor industry and related industries.

(7) R & D and production

Oer1ikon solar, a supplier of thin-film silicon solar cell modules, announced in early September 2007 that the company launched its micro cascade technology, combining amorphous silicon and microcrystalline silicon materials at the top and bottom of photovoltaic solar cells. The top layer of this micro cascade module technology is composed of amorphous silicon cells, which can convert visible light in the solar spectrum. The bottom microcrystalline silicon cell can absorb light in the infrared spectrum. This double-layer structure can improve the efficiency of this technology by about 50% compared with the traditional amorphous single-layer crystal cell. It is said that the potential efficiency of the new micro cascade technology is more than 10%, which can further reduce the cost of generating electricity per watt. All materials used in its thin film technology have the characteristics of non-toxic, low cost and easy application. The energy used for the bonding of this micro cascade module is only half of that of crystalline silicon battery.

Mitsubishi Electric Company of Japan announced on March 20, 2008 that it has successfully developed a 150 mm2 practical polycrystalline silicon solar cell with the world’s highest photovoltaic conversion efficiency of 18.6%. Its efficiency is 0.6% higher than the photovoltaic conversion efficiency of the company’s previous products. The conversion efficiency of solar cell units equipped with new technologies such as “honeycomb structure” disclosed in February 2008 has passed the test of the official certification body – Institute of industrial technology. The solar cell with photovoltaic conversion efficiency of 18.6% is made by adding a low reflection surface structure on the polycrystalline silicon wafer, which optimizes the N layer in the p-n junction, so as to improve the current generation. At the same time, by developing the process of printing the electrode on the silicon surface (metallization), the hiding loss of the front grid electrode is reduced by 25%. This technology can also have high efficiency in some small facilities, such as narrow roofs. Mitsubishi Electric will adopt this polysilicon cell technology in its mass-produced photovoltaic modules in 2011, and put forward the goal of increasing the annual output to 500MW in 2010. The company plans to use the key technology to achieve the highest value in the world – “honeycomb structure” for mass production after 2010. If the unit conversion efficiency can be increased from 16% to 18%, each 150mm2 battery unit can increase the output power by 0.4W. In this way, the output power of the module arranged by 50 battery cells can be increased by 20W. To form a “honeycomb structure”, it is necessary to use laser to punch 100 million small holes on the silicon nitride film formed on the surface of 150mm2 battery cells. In terms of mass production, how to improve the processing capacity of the laser processing equipment developed by the company is a major topic. If the processing capacity of laser processing equipment can be improved, the manufacturing cost per unit output power can be reduced.

Sharp announced in May 2008 that the conversion efficiency of its listed thin-film photovoltaic modules reached 14.4%. The polycrystalline silicon solar cell module “nd-191av” used in Japanese and Chinese houses not only improved the conversion efficiency, but also expanded the range that can be set on the roof. Compared with previous products, the average capacity that can be set on the roof is 1.5 times. The realization of high efficiency benefits from the change of surface electrode structure. The electrode of the solar cell is composed of a thicker bus bar electrode and a thinner finger electrode. This time, the bus bar electrode is increased from two to three, and the width of all electrodes is reduced. The increase of bus bar electrode shortens the electronic moving distance from finger to bus bar electrode, thus reducing the current collection loss, while the electrode becomes thinner, which can increase the light receiving area. Through these measures, the conversion efficiency has been improved. In addition, efforts have been made to improve the reflectivity of the back. The maximum output power of the unit module has reached 191w. The expansion of the settable range is realized by improving the wind pressure resistance. In the past, considering the wind expansion, it needs to be set 300 ~ 400mm away from the edge of the roof. This time, the product has improved the wind pressure resistance by improving the design of the rack and other means, Thus, it can be set 200 mm away from the edge of the roof.

The research team of Massachusetts Institute of Technology (MIT) announced that it has found a method to improve the conversion efficiency of thin-film solar cells by 50% μ The anti reflection film is arranged on the silicon film of M, and the multi-layer reflection film and diffraction grating are combined on the back of the solar cell, so that the output power of the solar cell is increased by about 50%. Due to the multi-layer reflection film arranged on the back of the solar cell, the sunlight can be reflected in the silicon film for a longer time, so the efficiency is improved, Peter berne1, a postdoctoral researcher at the Electronics Research Laboratory of MIT, who participated in the project, said that the key to improving efficiency is that the sunlight injected into the reflective layer of the solar cell passes through a long distance in silicon. The research team considered a variety of combinations of changes and repeated thousands of simulations for the width of the line grating, the thickness of silicon and the number of reflective film layers on the back of the solar cell.

Oetil1ion company of the United States cooperates with the University of Illinois to develop a new nano silicon photovoltaic solar cell technology. It can be used with glass windows to generate electricity by using sunlight. The power generation process has no great loss on the transparency of glass, but important changes need to be made to the manufacturing structure of windows. Oetil1ion takes the lead in developing the glass window of nano silicon photovoltaic solar cell, deposits the metal nano film on the glass window matrix, and uses the electronic injection system to deposit the fluorescent silicon nano particle film, which has high efficiency. The nano silicon photovoltaic solar cell generates electric energy through electrochemical process. With the help of highly luminous silicon nanoparticles, the quantum conversion efficiency for short wavelength is as high as 50% ~ 60%. When a silicon nanoparticle film is deposited (sprayed) on a silicon substrate, ultraviolet light can be absorbed and converted into electrical energy. Under appropriate bonding conditions, the silicon nanoparticle film becomes a nano silicon photovoltaic solar cell, which can convert solar radiation into electric energy.

Detong has developed a solar shutter curtain. The shutter is usually a simple and effective device to control indoor daylighting, while the German solar shutter curtain can absorb and store unnecessary light. At night, the sunny side of each blade of the shutter emperor has a thin flexible photoelectric film, which can convert sunlight into electric energy and store it in the charging pool. At night, the leaves emit soft light towards the indoor side to provide room background light. One 0.9m × The light emitted by the 1.8m solar shutter curtain with 14 blades is equivalent to the brightness of two 20W incandescent bulbs. In order to create different types of atmosphere, this electric fluorescence source can be adjusted to different colors from pure red to white. When the sun is sufficient, the solar shutter curtain can generate 49w electricity. In addition to lighting, the stored electric energy can also be used to drive other electrical appliances, such as ventilator, saving electric energy.

According to a paper published in the journal Science of the United States in July 2008 by a research team of Massachusetts Institute of technology, the team researchers have developed a new solar energy conversion system by using the mixed dyeing technology, which can convert solar energy into electric energy by using the windows of buildings. Mark bardo, the head of research and development, said that their design idea is to mix more than two dyes in a specific proportion, Paint on special glass windows. These dyes can absorb sunlight of different wavelengths, and then concentrate the sunlight on the solar cell at the edge of the window through the glass window. The solar cell is responsible for converting light energy into electric energy. Bardo said that in this way, the room window has become a new type of “solar window” to “guide” the sunlight and concentrate it on the solar cells on the four sides, The previous “solar cell concentrators” used large-area moving mirrors to track the sun’s concentration. Such a mirror has many disadvantages. Firstly, the installation and maintenance costs are expensive. Secondly, the solar cells located at the focus need to be cooled. The whole equipment occupies a lot of space, and it must be ensured that the concentrators will not block each other. In addition, people can only set up such concentrators in open areas such as the roof for photoelectric conversion. In contrast, “solar windows” take up less space, are easier to install and cost less. Bardo said that the system they developed is easy to produce, so they believe it can be popularized to the market within three years.

It is understood that due to the impact of global warming and high oil prices, solar cells relying on photoelectric conversion are known as one of the most promising green energy. Many companies, including Japanese consumer electronics manufacturer sharp and German Q cells, are carrying out research and development in the field of thin-film solar cells. However, compared with traditional solar cells, the low photoelectric conversion efficiency of thin-film solar cells has always been a difficult problem in the industry. American scientists have found an effective way to make silicon-based solar cells flexible enough to wrap them around an object the thickness of a pencil or attach them to the windows of buildings and even the glass surface of cars. The journal Nature materials, published on October 5, 2008, reported this achievement and said that this technology can transfer the previously fragile silicon wafer to flexible materials, which provides a new possibility for the traditional silicon slicing process. John, of the University of Illinois at champagne, who led the study? Rogers said that this technology will open the door to the promotion of new solar buildings. “We can make it thin enough, and then transfer it on a plastic sheet, so that it can be made into a crimpable system, so that a film similar to film thickness can be attached to the glass surface of the building.” Rogers said that this technology uses monocrystalline silicon with high photoelectric conversion efficiency as raw material. In order to overcome the shortcomings of extremely fragile monocrystalline silicon wafers, they used a special etching method to cut ultra-thin silicon wafers 10 ~ 100 times thinner than traditional silicon wafers from larger silicon crystals. It can be used in different fields according to its different thickness. When the silicon wafer is cut, it is picked up by a device and “transferred” to the surface of a new material like a seal. Finally, these cell like solar cells are connected into a whole with an electrical system. Compared with traditional solar panels, this highly flexible solar cell will be easier to transport and install. Rogers envisioned that the new material would be thrown into the car like a blanket.

Sharp of Japan launched an off grid independent thin-film silicon-based solar photovoltaic power generation system in May 2008, which is composed of solar cell modules and batteries. The application target is some off grid areas, such as Africa. The system was commercially produced and put into the market in 2010. The independent solar photovoltaic power generation system is composed of thin-film silicon-based solar cells of sharp and lithium-ion batteries produced by L and e1iy power companies. The solar cell is a series structure, and the conversion efficiency is 8.5% when used stably. When the temperature of polysilicon solar cell rises by 1 ℃, the conversion efficiency will decrease by 0.5%; The conversion efficiency loss of thin-film silicon-based solar cells is only 0.25% / C. Therefore, the photovoltaic power generation system using thin-film silicon-based solar cells is suitable for application in areas with high ambient temperature. The system is divided into two types: one is 90W solar cell module cascade 1024w H lithium ion battery; The other is 360W solar cell module cascade 4096w H lithium ion battery. Both systems are suitable for home use.

Fully charged tycorun lithium battery 1024w H can supply power for lighting equipment (5h for 1 day), radio (5h for 1 day) and electric fan (2H for 1 day) within 3 days. Fully charged 4096w H lithium ion battery can supply power for lighting equipment (4h a day), electric fan (2H a day), TV (2H a day) and refrigerator (24h a day) within 3 days.

Chinese researchers have developed thin-film amorphous silicon / microcrystalline silicon laminated solar cells with an area of 100cm2 and an efficiency of 9.83%. After 1000 hours of indoor light decay, the cell efficiency decay rate is less than 10%. The technical achievements of amorphous silicon cells and their combination with microcrystalline silicon solar cells to form laminated cells were obtained by the research group of the Institute of optoelectronics, School of information, Nankai University on the basis of completing the “973” plan “basic research on low-cost and long-life photovoltaic cells”. The research group has developed a series of key non-standard equipment and test systems necessary for the manufacture of thin-film solar cells, and established the only silicon-based thin-film solar cell development and production line with international advanced level in China.

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