Detailed explanation of high photoelectric conversion efficiency cells

Detailed explanation of high photoelectric conversion efficiency cells

Today’s most advanced and commercially available solar cells convert sunlight into electricity from the visible spectrum, however Spanish researchers have now developed a new material, a way to convert the infrared rays of the sunlight spectrum, sunlight Infrared light in the spectrum accounts for about half of the solar energy that can be converted into usable electricity. Conventional solar cells are based on semiconductor materials, and they cannot capture infrared light, which puts their theoretical limit on absorbing sunlight’s energy to just over 40%, while in practice, they can only absorb about 30% of sunlight’s energy, however , the new material can capture visible light and infrared light photons, so its theoretical maximum efficiency is 63%, which can greatly improve the actual performance of solar cells. For solar cells made of semiconductor materials, electricity is generated when the energy transferred by photons is absorbed by trapped electrons. Such cells can convert visible light, which hits Earth in large quantities but with not a lot of photon energy.

Since 1997 some researchers in Spain have developed battery methods to increase spectral utilization. Researchers led by Perla Wahnon, Faculty of Solar Energy, Polytechnic University, Spain, and Jose Conesa, Faculty of Catalysis, Spanish High-Tech Research Institute, designed new solar cell materials. They added titanium and vanadium atoms to conventional semiconductor materials, changing their electronic properties, creating intermediate energy levels. The Spanish team calculated that the material could theoretically capture sunlight with a 63 percent efficiency. The researchers noted that the actual efficiency of cells based on the new design cannot reach 63%, but if the theoretical limit is higher, the actual efficiency will be higher. Although such solar cells have not yet been manufactured, they are expected to appear in the near future.

Sun Power, a San Jose, California-based manufacturer of solar panels and batteries, has successfully increased the output power and size of solar panels, which is expected to significantly improve the power supply performance of existing panels. The company’s second-generation high-power product new panel went into production in 2007. The company claims to have successfully increased the output power of silicon cells from 20% to 22%. The new 5ft x 3.5ft panel can fit 96 cells, compared to 72 cells for existing products. Overall, these changes can improve power supply performance by 43%, producing 315W of electricity per panel, and the cost is about the same as today. The theoretical upper limit of the output power of monocrystalline silicon cells is about 25%, and other companies are also actively developing solar photovoltaic cell production technologies of other materials, especially CIGS.

Sun Power announced in mid-May 2008 that its solar cell efficiency had reached a world record, with a full-scale, 5in prototype solar cell produced by the company reaching 23.4% efficiency, up from 22% efficiency using Gen 2 technology Another lift.

National Semiconductor Corporation (National Semiconductor Corporation) announced in early July 2008, to enter the solar photovoltaic product market. The company’s new Solar Magic technology can effectively improve the power output efficiency of solar power generation systems. Even if the side-by-side panels are partially obscured by shadows, debris, or poor compatibility between panels, National Semiconductor’s Solar Magic technology can give full play to the efficiency of each solar photovoltaic panel, allowing the power generation system to give full play to the best performance . The solar power generation devices currently on the market can affect the power generation performance due to various problems such as shading, poor panel compatibility or accumulation of dirt.

For example, even if only a small portion of the solar panel is shaded, the solar energy received by the system is cut in half. This defect seriously affects the power output efficiency of ordinary civil solar power generation devices, and even the design and installation location of the system are greatly restricted. If the solar panels are shaded by shadows, the solar power generation system cannot even supply power to some household appliances in the house, and users will stop before the high cost of use because they cannot enjoy government preferential policies. National Semiconductor’s Solar Magic technology can restore 50% of lost solar energy, thereby minimizing the economic impact of environmental factors such as shading. Solar Magic technology ensures that each panel of a solar power system can operate independently, thereby The system can output the maximum power. Currently, solar power systems of various structures on the market are compatible with Solar Magic technology.

Scientists at the Massachusetts Institute of Technology (MIT) announced in mid-July 2008 that they have invented a method that can greatly improve the efficiency of polycrystalline silicon solar cells while maintaining low costs. They also established a technology company called “1366” to commercialize the technology. Emmanuel Sachs is a professor of mechanical engineering at MIT and one of the founders of the “1366” company. Small polycrystalline silicon solar cells about 2cm wide developed in his lab have a photoelectric conversion efficiency (the efficiency of converting a quantitative amount of light energy into electrical energy) that is 27% higher than ordinary polycrystalline silicon solar cells. Sachs uses three key inventions to improve the efficiency of solar cell models.

First, adding texture to the surface of the solar cell allows the silicon plate to absorb more light. When light enters the cell, the rough surface bends the light, and when the light reaches the back of the cell, it is not reflected directly, but bounces back at a small angle, where it resides in the silicon solar panel. The longer the light stays in the silicon plate, the greater the probability that it will be absorbed and converted into electricity. This technology has been used on monocrystalline silicon solar cells, but it has been difficult to achieve on polycrystalline silicon cells. The second invention is related to the silver wire that collects the current generated by the silicon plate. Sachs invented a technology that can make very thin silver wire, whose diameter is only 1/5 of the silver wire usually used in solar cells, and improves the electrical conductivity. Rate. The finer the silver wire, the lower the manufacturing cost. Compared with ordinary silver wires, the thin silver wires can be arranged more closely and have a smaller distance from each other, which makes the silver wires more efficient in collecting current.

The last invention was the use of a set of wide, flat metal strips to funnel the electrical current through a thin silver wire. Often, these metal strips block light from entering the solar cell, making the cell less efficient. But Sachs achieved the same effect as adding texture to the surface of a silicon plate by etching the surface of the metal strip to resemble a polygonal mirror. Although this process step will increase production costs, the amount of silver used is reduced, and the three can be offset. Generally speaking, polycrystalline silicon solar cells have lower conversion efficiency than expensive monocrystalline silicon solar cells, but they are much cheaper. The 27% efficiency improvement means that polycrystalline silicon solar cells can be produced at a lower cost with the same efficiency as monocrystalline silicon solar cells. Battery. Current solar cells cost $2.10 for every 1W of electricity they produce.

Scientists at the U.S. Department of Energy’s National Renewable Energy Laboratory announced on August 14, 2008 that they had achieved a solar cell photoelectric conversion efficiency of 40.8 percent, one of the highest efficiencies ever achieved by photovoltaic facilities. This inverse denatured triple junction solar cell was designed by NREL. Instead of using the wrong wafer as the bottom junction of the facility, the new design uses a complex like steel phosphate and steel-grafted arsenide to separate the solar spectrum into three identical components that are captured by each of the cell’s three junctions. absorption, and thus a higher potential efficiency. The facility is extremely thin and lightweight, and its advantages in performance, design, operation and cost represent a new breed of solar cells.

Suniva announced on September 23, 2008 that it has successfully developed several new silicon-based solar cells. Using its patented cell design and shielding printing technology, the photoelectric conversion efficiency of solar cells can reach 20%. This landmark high efficiency has been demonstrated by the National Renewable Energy Laboratory. The company has signed technology transfer contracts worth about $1 billion with Germany’s Solon and India’s Energy Systems. Suniva’s advanced technologies in diffusion, surface passivation and contact are said to enable improved conversion efficiency, reduced processing time, and low cell maintenance costs.

Innova1ight, a US supplier of printed silicon ink solar cell technology, announced on September 8, 2009 that the conversion efficiency of its silicon ink process solar cells has reached a record 18%. With Innova1ight’s proprietary silicon ink and processing technology, crystalline silicon solar cell manufacturers can greatly increase production capacity and solar cell performance while reducing costs by simply adding a simple link to an already installed production line. Currently, Inova1ight
It is actively cooperating with a number of solar cell manufacturers and increasing its silicon ink production scale. At the same time, the company is continuing to carry out technology research and development on the basis of existing silicon ink, and strive to increase the conversion efficiency of solar cells to more than 20%.

Japan Industrial Technology Research Institute announced in late September, 2008 that it has developed a new type of high-efficiency compound solar cell material that can be mass-produced. This material is made by spraying the copper-coated steel composite material on the glass substrate in the crucible at 300~500 ℃, which can form crystals with higher purity in the power generation layer to improve the conversion efficiency of solar energy. After testing, solar cells made of new materials have converted 14.9% of solar energy into electricity, while some current products have a conversion rate of 10% to 12%. This technology was developed by the Institute’s Solar Power Research Center. The institute will transfer the technology to companies to commercialize it within two years.

Researchers at the Fraunhofer Institute for Solar Energy Systems in Freiburg, Germany, announced on September 30, 2008 that they had achieved a multi-junction solar cell efficiency of 39.7%, surpassing their previous record of 37.6% set in July. This achievement is achieved using multi-junction solar cells made of IIIV semiconductors, which have been used in concentrating photovoltaics in solar power plants. This technology improves the contact structure of the solar cell and achieves higher efficiency using the same semiconductor structure.

Suntech Power Holdings announced on March 30, 2009 that the photoelectric conversion efficiency of solar photovoltaic cells produced by using its Pluto technology can be increased to about 19% for monocrystalline silicon PV cells and 17% for polycrystalline silicon PV cells. Its cell products were sent to Germany’s Fraunhofer Institute for Solar Energy Systems (ISE) for third-party certification. The Fraunhofer Institute for Solar Energy Systems’ tests showed that the photoelectric conversion efficiency of monocrystalline silicon Pluto PV cells is 18.8%, and the photoelectric conversion efficiency of polycrystalline silicon Pluto PV cells is 18.8%. At 17.2%, Suntech’s two PV cells have been produced on a 34MW Pluto line using solar-grade silicon wafers.

In comparison, the photoelectric conversion efficiencies of the two PV cells are 16.5% and 15.5%, respectively, using conventional shield printing technology. The patented Pluto technology is based on PERL technology developed by the University of New South Wales in Australia, which can reach the world in the laboratory. With a record conversion efficiency of 25%, the power output using Pluto technology can be approximately 12% higher than that of conventional shielded printed PV cell technology. The Pluto system uses a unique material structure technology with lower light reflectivity. It ensures that the battery absorbs more light throughout the day, and the thinner metal lines on the upper surface reduce shading losses. Suntech’s Pluto technology is available in different grades of silicon to support a variety of applications and product types. Suntech will also improve the Pluto technology, aiming to make the photoelectric conversion efficiency of monocrystalline silicon Pluto PV cells reach 20%, and the photoelectric conversion efficiency of polycrystalline silicon Pluto PV cells to reach 18% in the next two years.

German photovoltaic company Q Cells announced on September 18, 2009 that the conversion efficiency of polycrystalline silicon solar cells (certified by the Fraunhofer Institute for Solar Energy Systems) reached 15.9%, which is a world record for mass production using conventional industrial standards, Q Cells The company has invested 50 million euros to build a 249W module medium production line in Tha1heim, Germany.

Sun Power announced at the end of October 2009 that the photoelectric conversion efficiency of the total area of ​​its large-scale solar panels broke a record of 20.4%. This conversion efficiency has been certified by an independent testing facility at the National Renewable Energy Laboratory in the United States. Sun Power expects a 20.4% efficiency solar panel to be commercialized within two years. The company plans to use automated equipment to start production in 2010. factory. Sun Power also announced the availability of the applicable Sun Power T5 solar roof tile, the first rooftop PV product to combine solar panels, frames and mounting systems in a single pre-engineered unit.

Sharp Corporation announced on October 29, 2009 that it has developed a solar cell with the highest conversion efficiency in the world (for non-concentrating solar cells) using triple-combined composite solar cells, which is comparable to the most commonly used solar cells today, namely silicon-based solar cells. Unlike solar cells, this composite solar cell uses a light-absorbing layer, which is made of a composite of two or more elements, such as steel and magnesium. Due to their high conversion efficiency, composite solar cells are mainly used in space satellites. Since 2000, Sharp Corporation has been advancing the research and development of triple-junction composite solar cells, which achieve high conversion efficiency by stacking three light-absorbing layers.

In order to improve the efficiency of triple-combined composite solar cells, it is important to improve the crystallinity (ie, regular atomic arrangement) of each light-absorbing layer (upper, middle, and lower layers), and the composition of cell materials is also crucial. To maximize the efficient use of solar energy, Ge (germanium) is traditionally used as the bottom layer because it is easy to manufacture. However, in terms of performance, although Ge can generate a large amount of current, a large amount of current is wasted and cannot be used effectively for power generation. The key to solving this problem is to form the bottom layer composed of InGaAs (Indium Gallium Arsenide), which has high light utilization efficiency. However, it is difficult to manufacture high-quality InGaAs with high crystallinity, and Sharp Corporation has succeeded in constructing high-crystallinity steel heald layers by using its own proprietary shape-layer technology. Therefore, the amount of current wasted can be minimized, and Sharp can successfully increase the conversion efficiency to 35.8% on the basis of the previous cell conversion efficiency of 31.5%.

REC and the Netherlands Energy Research Center (ECN) announced in mid-December 2009 that they have produced the world’s first polysilicon solar panels with a conversion efficiency of 17%, breaking through the 16.5% polysilicon solar photovoltaic module created by Suntech in September. Conversion efficiency records. The world record was jointly created by polycrystalline silicon solar wafer manufacturer REC Corporation and the Energy Research Centre of the Netherlands (ECN). European Solar Testing Station (ESTI has certified it for functional testing according to standard test conditions.

The efficiencies of crystalline and amorphous silicon are achieved through the use of synthetic sensitizers and emitter molecules in solar cells. This “single-threshold material” generates a voltage above which electrons are generated by absorbing light above this threshold, below which energy photons cannot be harvested. The maximum photoelectric conversion efficiency of a single-threshold PV inverter is about 30%, and one way to improve efficiency is to place a frequency-converting substance on the back of the cell to convert subthreshold photons into usable light; such cells have an efficiency limit greater than 50%, their work specifically focuses on the use of “triplet triplet layouts” in organic molecules.

When two triplet emitter molecules come into contact with each other, the result is a single, triplet, or quintuple spin state, if singlet (1:9 probability), it can switch to a lower energy state and fluoresce , producing “frequency-converted” light. Using this “variable” approach, results were significantly improved, with efficiency limits in excess of 50% in the standard solar spectrum and as high as 63% at 100 times the intensity of sunlight.

The California Institute of Technology announced in early March 2010 that it had developed a new type of solar cell, the basic principle of which is to embed an array of slender silicon wires into a polymer substrate. In addition to being thin and flexible, it has made great breakthroughs in both sunlight absorption and photoelectric conversion efficiency. In addition, the new type of solar cell requires only a fraction of the amount of expensive semiconductor material required by conventional solar cells. “These solar cells push the light-harvesting limit of traditional light-absorbing materials for the first time,” said Harry Atwater and Howard Hughes, professors of applied physics and materials. The silicon wire arrays used in the new solar cells absorb a single wavelength of incident light as high as 96% and 85% of full-wavelength sunlight, Atwater pointed out: “Many materials are good at capturing light, but cannot convert it into electricity, such as black paint.

For solar cells, it is also very important whether the absorbed photons can be converted into charge carriers. “The silicon wire array solar cells they developed can convert 90% to 100% of the absorbed photons into electrons, technically speaking, the array has a near-perfect internal quantum efficiency.” Atwater concluded: “For light The high absorption rate and good conversion ability of the solar cells contribute to the high quality of this solar cell. “The silicon wire in the silicon wire array is 30~100μm in length and only 1μm in diameter, and the thickness of the entire array is equivalent to the length of the silicon wire, but from an area or volume perspective, only 2% of this material is silicon, The other 98% is polymer. Since silicon is an expensive ingredient in conventional solar cells, a solar cell that requires only 1/50th of the conventional amount would be much cheaper to put into production.

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