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What is the maximum power of a solar cell can provide?

Assuming the arbitrary intensity light is available, what is limiting the maximum output of a solar cell can provide a given area? What causes this limitation? Assuming light of arbitrary intensity is available, what is the limitation of the maximum power of a solar cell can provide for a given surface? What causes this limitation? I'm not talking about 1000 W / m ^ 2 standard solar heat flux. I've seen the Fresnel lens to intensify this almost a point, leaving a large area of energy a small solar cell in a heat flow of hundreds of suns. What are the limits to do this? Heat is an obvious problem, but there are others? This has nothing to do with efficiency. Assume an arbitrary (or infinite) number of photons are cheaply available.

A solar cell (or "energy photovoltaic "cell) is a semiconductor device that converts photons from the sun (sunlight) into electricity. In general, a solar cell, which includes both energy Solar and solar sources of light (such as photons from incandescent bulbs) is termed a photovoltaic cell. Fundamentally, the device must meet only two functions: photogeneration of charge carriers (electrons and holes) in a material that absorbs light, and the charge separation of carriers to contact drivers transmitting electricity. This conversion is called the photovoltaic effect, and the field of research related to solar cells known as photovoltaics. Solar cells have many applications. Historically solar cells have been used in situations where electrical power network is not available, as in remote area power systems, satellites orbiting the Earth, consumer systems, such as calculators or watches, remote radiotelephones and water pumping applications. Recently, solar cells are particularly used in assemblies of solar modules (photovoltaic arrays) connected to the mains through an inverter, often in combination with a net metering agreement. Solar cells are regarded as one of the key technologies towards a sustainable energy supply. Three generations of development [edit] First, the first generation photovoltaic, consists of a large area, single-layer PN junction diode that is capable of generating usable electrical energy from light sources with wavelengths of sunlight. These cells are typically made using silicon wafers. First generation photovoltaic cells (also known as silicon wafer-based solar cells) are the dominant technology in production commercial solar cells, which represent over 86% of the solar cell market. [edit] The second generation of photovoltaic materials is based on the use of thin-film deposits of semiconductors. These devices were initially designed for high efficiency, multiple junction photovoltaic cells. Later, the advantage of using a thin film of material was noted, reducing the mass of material required for cell design. This contributed to a prediction of greatly reduced costs for thin film solar cells. However, most of the assembly costs for the deposition of solar cells thin film are significantly higher than those of bulk silicon technologies. Another advantage of the reduced mass is that less support is needed to put panels on the roofs and allows the installation panels from lightweight materials, including textiles. [edit] Third generation photovoltaic third are very different from the other two, broadly as semiconductor devices that are not based on a traditional pn junction to separate photogenerated charge carriers. These new devices include photoelectrochemical cells, polymer solar cells, and nanocrystal solar cells. [edit] History Main article: Timeline solar cells The term "photovoltaic" comes from the Greek φώς: Phos which means "light" and the name of the Italian physicist Volta, after the voltage (voltage and thus) are appointed. This means, literally, light and electricity. The photovoltaic effect was recognized for the first time in 1839 by French physicist Alexandre-Edmond Becquerel. However, it was not until 1883 when they built the first solar cell, by Charles Fritts, which covered the semiconductor selenium with a very thin layer of gold to form unions. The device was only about 1% efficiency. Russell Ohl patented the modern solar cell in 1946 (US2402662, "Light sensitive device"). Sven Ason Berglund had a prior patent concerning methods of increasing the capacity of photosensitive cells. The modern era of solar power technology arrived in 1954 when Bell Laboratories, experimenting with semiconductors, accidentally found that silicon doped with certain impurities was very sensitive to light. This resulted in the production of the first practical solar cells with a sunlight conversion efficiency of energy of around 6 percent. This milestone created interest in producing and launching a geostationary communications satellite, providing an energy source viable. Russia launched the first artificial satellite in 1957, and the United States the first artificial satellite was launched in 1958. Russian Sputnik 3 ( "Satellite-3"), launched on 15 May 1957, was the first satellite to use solar panels. This was a crucial fact that the diverted funds from several governments into research to improve solar cells. [Edit] Applications and implementations of Polycrystalline photovoltaic cells laminated to backing material in an article moduleMain PV: cell matrix solar photovoltaics are often electrically connected and encapsulated as a module. PV modules often have a sheet of glass in the front (toward the sun above) on the side of a barrier resin behind, allowing light to pass while protecting the semiconductor wafers from the elements (rain, hail, etc..) Solar The cells are usually connected in series in modules, creating an additive voltage. Connecting cells in parallel will produce a higher amperage. Modules Here are interconnected in series or in parallel, or both, to create an array with the desired peak DC voltage and amperage. [edit] Theory [edit] simple explanation photons of sunlight hit the solar panel and are absorbed by semiconducting materials like silicon. electrons (negatively charged) are knocked loose from their atoms, allowing them to flow through the material to produce electricity. The complementary positive charges that are also created (like bubbles) are called holes and flow in the opposite direction of the electrons in a silicon solar panel. A series of solar panels converts solar energy into a usable amount of direct current (current continuous). Optionally: the direct current between an investor. The inverter converts DC electricity into 120 or 230-volt AC (alternating current) electricity needed for appliances. The AC power enters the utility panel in the house. The electricity is distributed to appliances or lights in the house. The electricity not used will be recycled and reused in other facilities. [edit] Cargo carriers Photogeneration When a photon hits a piece of silicon, one of three things may happen: the photon can pass straight through the silicon – this (generally) happens for lower energy photons, the photons are reflected from the surface, the photon can be absorbed by silicon, it generates heat, or electron-hole pairs generated if the photon energy is greater than the value of the silicon band gap. Note that if a photon has an integer multiple of the energy of The Gap Band, you can create more than one electron-hole pair. However, this effect is usually not significant in cells solar. The "integer multiple" part is a consequence of quantum mechanics and the quantization of energy. When a photon is absorbed, its energy given to an electron in the crystal lattice. Usually this electron is in the valence band, and is tightly bound in covalent bonds between neighboring atoms, and therefore, unable to move now. The energy is given by the photon "excites" it into the conduction band, where he is free to move within the semiconductor. The covalent bond that the electron was previously a part of now has one less electron – this is known as a hole. The presence of a missing covalent bond allows electrons of neighboring atoms bonded to enter the "hole," leaving another hole behind, and in this way a hole can move through network. Thus, one can say that photons absorbed in the semiconductor create mobile electron-hole pairs. A photon does not need more than an energy greater than the of the band in order to excite an electron from the valence band into the conduction band. However, the frequency spectrum of the solar spectrum approximates a black body to ~ 6000 K, and as such, much of the solar radiation reaching Earth is composed of photons with energies greater than the silicon band. These photons of high energy will be absorbed by the solar cell, but the difference in energy between these photons and the band gap of silicon is converted to heat (through vibrations network – called phonons) rather than into usable electrical energy. [edit] Burden of separation company There are two main modes for charge separation carriers in a solar cell: the drift of carriers, driven by an electrostatic field established across the device diffusion of carriers areas of high carrier concentration to zones of low carrier concentration (following an electrochemical potential gradient). In widely used pn junction solar cells, the dominant mode of charge separation carrier for the drift. However, non-junction cells designed solar (typical of the third generation of solar cell research such as dye and polymer thin film solar cells), a field Electrostatic general has been confirmed to be absent, and the dominant mode of separation is through the diffusion of charge carriers. [edit] The pn junction Main article: the best-known semiconductor solar cells as a large area pn junction made from silicon. To simplify, one can imagine put a layer of n-type silicon into direct contact with a p-type silicon layer In practice, pn junctions of silicon solar cells are not made in this way, but, to disseminate an n-type dopant into one side of a p-type wafer (or vice versa). If a piece of p-type silicon is placed in intimate contact with a piece of n-type silicon, then a diffusion of electrons occurs in the region of high electron concentration (the n-type side of the union) in the region of the electron concentration low (p-type side of the junction). When the electrons diffuse across the pn junction, they recombine with holes in the p-type side The diffusion of carriers does not happen indefinitely however, because of an electric field is created by the imbalance of charge immediately on either side of the union that created this broadcast. The field electric established through the pn junction creates a diode that promotes current flow in one direction through the junction. Electrons can move from n-type side into the p-type side and holes may pass from the P-type side to n-type side This region where electrons have diffused across the junction is called the depletion region because it no longer contains any mobile charge carriers. It is also known as the "space charge region. [edit] The connection to an external load metal-semiconductor ohmic contacts are made both in the N-type and P-type side of the solar cell and the electrodes connected to an external load. Electrons are created in the n-type side, or have been "collected" by the union and swept into the n-type side, may travel through the cable, the power load, and continue through the cable to reach the P-type semiconductor-metal contact. Here, they recombine with a hole that was either created as an electron-hole pair on the side P type of solar cell, or crossed the intersection of the N-type side after being created there. [edit] Equivalent circuit of a solar cell, the equivalent circuit of a solar cell The schematic symbol of a solar CELLT understand the electronic behavior of a solar cell, is useful for creating a model that is electrically equivalent, and is based on discrete electrical components whose behavior is well known. An ideal solar cell can be modeled by a current source in parallel with a diode. In practice, no solar cell is ideal, so a shunt resistance and a component of the series resistance added to the model. The result is the "equivalent circuit of a solar cell" shown on the left. Also shown on the right is the schematic representation a solar cell for use in circuit diagrams. [Edit] Factors solar cell efficiency [edit] A Maximum Power Point solar cell can operate in a wide voltage range (V) and currents (I). By increasing the resistive load (voltage) in the cell of zero (indicating a short circuit) to infinity for high values (indicating open circuit) one can determine the point of maximum power (maximum output power, Vmax x Imax, or PM, in watts). [edit] efficiency conversion of solar energy conversion A cell efficiency (η, "ETA") is the energy conversion rate (absorption of light into electrical energy) and collected when a solar cell is connected to an electrical circuit. This term is calculated from the ratio of the PM, divided by the input light irradiance under "normal" test conditions (E, in W / m 2) and the solar cell surface (BC in m²). A solar noon on a clear day in March or September equinox, solar radiation in Ecuador is 1000 W/m2. Therefore, the "standard" solar radiation (known as "air mass 1.5 spectrum") has a power density of 1000 watts per square meter. Thus, 12% cell efficiency 1 m² solar surface in full sunlight at solar noon in Ecuador during the equinox either March or September will produce approximately 120 watts of power peak. [edit] Another factor of filling in the term that defines the overall behavior of a solar cell is the fill factor (FF). This is why the point of maximum power divided by the open circuit voltage (Voc) and short circuit current (Isc): [edit] Quantum efficiency Quantum Efficiency refers to the percentage of absorbed photons that produce electron-hole pairs (or charge carriers). This is a term intrinsic to the light absorbent material, not the cell as a whole (which becomes more relevant for thin-film solar cells). This term should not be confused with energy conversion efficiency as not convey information about the energy collected from the solar cell. [edit] Comparison of energy conversion efficiencies principal Article: Photovoltaic efficiency silicon solar cells range from 6% based on amorphous silicon solar cells and 30% or more with various cells of the joint laboratory of the research. The conversion efficiency solar cells for MC If commercially available solar cells are around 14-16%. The cells of high efficiency has not always been the most economical – for example, 30% efficient multijunction cell based on exotic materials like gallium arsenide or indium selenide and produced in low volumes and can cost a hundred times as much as 8% efficient amorphous silicon cell in mass production, while only delivering a little less than four times the power. To make practical use of solar generated electricity is more often to feed the electricity network using inverters (grid-connected photovoltaic systems), and stand alone systems, batteries are used to store the electricity not needed immediately. A common method used to express the economic costs of electricity generation systems, is to calculate a price per delivered kilowatt-hour (kWh). Efficiency solar cell in combination with the available irradiation has a major influence on costs, but in general the overall system efficiency is important. Using cells plots available in the market (from 2006) and system technology can improve system efficiency 5 to 19%. Since 2005, the cost of photovoltaic generation electricity ranged from ~ 50 euro cents / kWh (0.60 U.S. $ / kWh) (central Europe) to ~ 25 cents / kWh (U.S. $ 0.30 / KWh) in regions of high solar irradiation. This electricity is generally fed into the grid on the client side of the meter. The cost can be compared with electricity prices charged to retail (in 2005), which varied between 0.04 and 0.50 U.S. worldwide $ / kWh. (Note: In addition to the profiles of solar radiation, these costs / kWh estimates vary depending on the assumptions for years of useful life of a system. Most c-Si panels are guaranteed for 25 years and should see 35 + year life.) The graph at right illustrates the various commercial large-area module energy conversion efficiency and the best laboratory efficiencies obtained for various materials and technologies. Timeline reported conversion efficiency of solar cells for energy (from National Renewable Energy Laboratory (USA) [edit] watt peak (or peak watts) Since the production of solar cells depends on multiple factors, such as angle of incidence of the sun, for comparison purposes between different cells and panels, used peak watt (Wp). It is the power output under these conditions: [1] solar radiation 1000 W / m² solar reference spectrum AM (airmass) 1.5 cell temperature 25 ° C [edit] Solar cells and recovery energy exists a common understanding that solar cells never produce more energy than it takes to make them. While the expected working life is about 40, the energy recovery time of a solar panel is 1 to 20 years (usually under five) depending on the type and where it is used (see net energy gain). This means that solar cells can be net energy producers and can "reproduce" themselves (from just over once for more than 30 times) throughout his life. [2] [3] This is discussed, however, by some researchers who object that this analysis does not account for waste, inefficiencies and energy-related costs that come with a solar cell in the real world. [4] [edit] Materials that absorb light all solar cells require material absorption of light contained within the cell structure to absorb photons and generate electrons via the photovoltaic effect. The materials used in solar cells tend to have the ability to absorb preferentially the wavelength of sunlight reaching the earth's surface, however, some solar cells are optimized for light absorption beyond Earth's atmosphere as well. Light-absorbing materials can often be used in multiple physical configurations to take advantage of different light absorption and charge separation mechanisms (listed in alphabetical order). Many solar cells available today are configured as bulk materials which are then sliced and is "top down" method of synthesis (silicon is the most prevalent bulk material). Other materials that are configured as thin films (inorganic layers, organic dyes and polymers organic) that are deposited on supporting substrates, while a third group are used as quantum dots (electron-confined nanoparticles) embedded in an array of support at the bottom of a "top". Silicon remains the only material that is well documented, both in volume and thin-film configurations. [edit] The bulk bulk technologies is often referred to as wafer fabrication. In other words, in each of these approaches, self-supporting wafers between 180 to 240 micrometers thick are processed and then welded together to form a solar cell module. A general description of silicon wafer processing is provided in the manufacture and Devices. [Edit] Silicon Main article: silicon and list of silicon producers by far the most common bulk material of crystalline silicon solar cells (abbreviated as a group as c-Si), also known as "solar grade silicon. Bulk silicon is divided into several categories as crystallinity and crystal size in the resulting ingot, ribbon, or wafer. Monocrystalline silicon (c-Si): often used the Czochralski process. Single-cell glass wafer tend to be expensive, and because they are cut from cylindrical ingots, not completely cover a solar cell module of the square without a substantial loss refined silicon. Hence most c-Si panels have uncovered gaps at the corners of four cells. Poly-or polycrystalline silicon (poly-Si or mc-Si): from cast square ingots – large blocks of molten silicon carefully cooled and solidified. These cells are less expensive to produce than glass cells unique, but are less efficient. Silicon Tape: formed by drawing flat thin films of molten silicon and has a polycrystalline structure. These cells have a efficiency lower than poly-Si, but save on production costs due to a large reduction in silicon waste, as this approach does not require sawing from ingots. [edit] Thin films The different thin film technologies currently being developed to reduce the amount (or mass) of light absorbing material required in the creation of a solar cell. This can lead to reduced costs of processing of bulk materials (in the case of silicon thin films) but also tends to reduce the energy conversion efficiency, although many of multilayer thin films have efficiencies above those of bulk silicon wafers. [edit] CdTe cadmium telluride is an efficient light-absorbing material thin film solar cells. Compared to other film materials thin CdTe is easier to deposit and more suitable for large scale production. Despite much discussion about the toxicity of CdTe-based solar cells, this is the only technology (apart from amorphous silicon) that can be delivered on a large scale, as shown by First Solar and Antec Solar. There is a 40-megawatt plant in Ohio (USA) and a 10 MW plant in Germany. First Solar is expanding to a 100 MW plant in Germany. The perception of the toxicity of CdTe is based on the toxicity of cadmium elementary. However, it is possible that the toxic elements that combine to form a harmless compound, as in the example of sodium chloride, better known as common salt, which is highly reactive sodium metal and chlorine gas corrosive and poisonous. The scientific work, particularly by researchers of Energy National Laboratory Renewable (NREL) of USA, has shown that the release of cadmium into the atmosphere is lower with CdTe-based solar cells with silicon photovoltaics and other thin film technologies of solar cells. [edit] CIGS CIGS are multi-layer thin film composites. The abbreviations mean indium gallium selenide copper. Unlike the basic silicon solar cell, which can be modeled as a simple pn junction (see semiconductor), these cells are better described by a more complex heterojunction model. The best efficiency of a thin layer cell in December 2005 was 19.5% with CIGS. Higher efficiencies (around 30%) can be obtained by using optics to concentrate the incident light. Since 2006, the best conversion efficiency of flexible CIGS cells on polyimide is 14.1% in Torres et al, the ETH, Switzerland. The use of indium increases the gap of the CIGS layer, gallium is added to replace the Indian as well as the relative availability of gallium possible by the Indian. Approximately 70% [5] Indian currently produced is used by the industry flat screen monitor. Some investors in technology concerns solar CIGS cell production will be limited by the availability of indium. 2GW production of CIGS cells (approximately the number of cells silicon produced in 2006) used approximately 10% of Indian production in 2006. [edit] Nanosolar says that waste only 5% of the Indian who uses and suggests that the vacuum spray technology Daystar, tend to lose about 60% of the Indian. Selenium allows for better uniformity in the layer and what the number of recombination sites in the film, which reduces the benefits of quantum efficiency and therefore the conversion efficiency. [edit] Community of Independent States CIS is an abbreviation for general chalcogenide films of copper indium selenide (CuInSe2). While these movies work can achieve 11% efficiency, production costs are high, but today is still being more cost-effective production processes. A manufacturing plant was built in Germany by Würth Solar. It was opened in October 2006. Full production is planned for late 2006. [Edit] gallium arsenide (GaAs) high-efficiency multijunction The cells have been developed for special applications such as satellites and space exploration that require high performance. These multijunction cells consist multiple thin films produced using molecular beam epitaxy. A triple-junction cell, for example, consist of semiconductors: GaAs, Ge, and GaInP2. [6] Each type of semiconductor will have a characteristic energy of the band that, in general terms, it makes more effectively absorb light in a given color, or more precisely, to absorb electromagnetic radiation over a portion of the spectrum. The semiconductors are carefully chosen to absorb nearly all the solar spectrum, thus generating electricity from as much solar energy as possible. GaAs multijunction devices are solar cells more effective to date, reaching as high as 39% efficiency. [7] also are among the most expensive cells per unit area (up to U.S. $ 40/cm ²). [edit] light absorbing dyes Main article: Dye-sensitized solar cells normally ruthenium metalorganic dye (Ru-centered) used as a monolayer light-absorbing material. The dye-sensitized solar cell depends on a layer of mesoporous nanoparticles of titanium dioxide to greatly expand the surface (200-300 m² / g TiO2, compared with about 10 m² / gram single crystal plane). The photogenerated electrons from the light absorption of dye are passed the N-type TiO2, and the holes are passed to an electrolyte on the other side of the dye. The circuit is completed by a redox couple in the electrolyte, which may be liquid or solid. This type of cells allows more flexible use of materials, and typically are manufactured by screen printing, with the potential to reduce processing costs than those used for most solar cells. However, the dyes in these cells also suffer from degradation under heat and UV light, and the casing of the cell is difficult sealing due to the solvents used in assembly. Despite this, This is a popular emerging technology with some commercial impact expected in this decade. [edit] organic polymer solar cells and organic solar cells and polymer solar cells are constructed from thin films (typically 100 nm) of organic semiconductors such as polymers and small molecule compounds phenylene vinylene, copper phthalocyanine (a blue or green organic pigment) and carbon fullerenes. The energy conversion efficiencies achieved to date using conductive polymers are low at 4-5% efficiency for the best cells to date. However, these cells could be beneficial for some applications where flexibility and ease of mechanical layout are important. [edit] Silicon silicon thin films are mainly deposited by chemical vapor deposition (typically plasma enhanced (PE-CVD)) from silane gas and hydrogen. Depending on the parameters of the shell, this can occur: amorphous silicon (a-Si or a-Si: H) protocrystalline silicon or nanocrystalline silicon (nc-Si or nc-Si: H). These types of silicon present dangling and twisted bonds, which results in deep defects (energy levels in the band gap) as well as deformation of the valence bands and conduction (band tails). Solar cells made from these materials tend to have lower energy conversion efficiency than bulk silicon, but are also less expensive to produce. The quantum efficiency of thin film solar cells is also lower due to reduced number of charge carriers collected per incident photon. Amorphous silicon has a larger gap (1.7 eV) of crystalline silicon (c-Si) (1.1 eV), which means it is more efficient to absorb the visible solar spectrum, but could not collect the infrared portion of the spectrum. As nc-Si has about the same bandgap c-Si, the two materials can be combined in thin layers, creating a layer of cells called tandem cell. The top cell of a-Si absorbs the visible light and leaves the infrared part of spectrum for the bottom cell in nanocrystalline If. The technology of thin-film silicon is being developed for building integrated photovoltaics (BIPV) in the form of semi-transparent cells lots that can be applied as window panes. These cells function as window tinting while generating electricity. [Edit] nanocrystalline solar cells Main Article: Nanocrystal Solar Cells These structures make use of some of the same thin-film light absorbing materials but are covered as extremely thin absorber on a support matrix polymer conductors or mesoporous metal oxide with a high surface to increase internal reflections (and therefore increase the probability of light absorption). [edit] Concentrating Photovoltaics (CPV) Concentrating photovoltaic systems use a wide surface of the lenses or mirrors to focus sunlight on a small area of photovoltaic cells. [8] If these systems use single or double axle – monitoring to improve performance that can be called Heliostat Concentrator Photovoltaics (HCPV). The main attraction of CPV systems is their reduced usage of semiconducting material that is currently expensive and scarce. Moreover, increasing the concentration ratio improves the overall performance of photovoltaic materials [9], and also allows the use of high performance materials such as gallium arsenide. [10] Despite the advantages of CPV technologies their application has been limited by the costs of focusing, tracking and cooling equipment. On 25 October 2006, Australia announced that the construction of a solar plant using this technology to come online in 2008 and completed in 2013. This plant of 154 MW, could be ten times larger than the largest current photovoltaic plant in the world. [11] [edit] manufacture of silicon solar Since cell solar cells are semiconductor devices that share many of the same processing and manufacturing techniques of semiconductor devices such as computers and memory chips. However, the stringent requirements of cleanliness and quality control of semiconductor fabrication are a little more relaxed for the cells solar. Most large-scale commercial solar cell factories today make screen printed poly-crystalline silicon solar cells. Single crystalline wafers which are used in the semiconductor industry can make excellent high efficiency solar cells, but is generally considered too expensive for mass production. Poly-wafer crystalline silicon are made by wire-sawing block-cast silicon ingots into very thin micrometer (180 to 350) slices or wafers. The wafers are usually slightly p-type doping. To make a solar cell wafer, a surface diffusion of N-type doping is performed in front of the wafer. This forms a pn junction a few hundred nanometers of the surface. Antireflective coatings, which increase the amount of light near the solar cell, are typically applied next. During the last decade, silicon nitride has gradually replaced titanium dioxide as the anti-reflection coating of choice because of its excellent qualities passivation surface (ie company avoids recombination on the surface of the solar cell). Normally a layer several hundred nanometers thick using plasma enhanced chemical vapor deposition (PECVD). Some solar cells against textured surfaces, such as antireflection coatings, serve to increase the amount light, next to the cell. Such surfaces can usually only formed in monocrystalline silicon, although in recent years the methods of forming them polycrystalline silicon have been developed. The wafer is then metallized, whereby a complete data area is performed on the metal back surface, and a grid-like contact formed by thin metal "fingers" and larger "bars" is screen printed on the front surface with a silver paste. The subsequent contact is also formed by screen printing a paste of metal, usually aluminum. Usually this covers the back of the cell, although in some cell designs that is printed in a grid pattern. The metal electrodes will require some type of heat treatment or "sintering" to make contact ohmic with silicon. After making the metal contacts, interconnect solar cells in series (and / or parallel) by flat wires or metal ribbons, and assembled in modules or solar panels. "Solar panels have a sheet of tempered glass on the front, and a polymer encapsulation on the back. Tempered glass can not be used with amorphous silicon cells because of the high temperatures during the deposition process. [Edit] Current research on materials and devices Main Article: Timeline of solar cells There are many research groups working in the field of photovoltaics in universities and research institutions worldwide. This research can be divided into three areas: manufacturing technology of today's solar cells Cheap and / or more efficient to compete effectively with other energy sources, developing new technologies based on new solar cell architectural designs and development of new materials to serve as light absorbers and charge carriers. [edit] silicon processing One way is to develop more Cheap to obtain silicon that is sufficiently pure. Silicon is a very common element, but is normally bound in silica or silica sand. Processing of silica (SiO2) to produce silicon is a very high energy process, not more energy efficient methods of synthesis are only beneficial for the solar industry, but also to industries surrounding silicon technology as a whole. The current industrial production of silicon is via the reaction between carbon (charcoal) and silica at a temperature of about 1700 degrees Celsius. In this process, known as carbothermic reduction, each tonne of silicon (metallurgical grade, about 98% purity) is produced by the emission of about 1.5 tonnes of carbon dioxide. solid silica can be directly converted (reduced) to pure silicon by electrolysis on a molten salt bath at a temperature quite mild (800 to 900 degrees Celsius). [12] [13] While this new process is in principle the same as the FFC Cambridge process, which was discovered in late 1996, the interesting laboratory finding is that such electrolytic silicon is in the form of porous silicon that is easily converted into a fine powder (with a particle size of a few micrometers), and thus may offer new opportunities for the development of solar cell technologies. Another approach is to also reduce the amount of silicon used and hence costs, as has Australia's National University in the production of their "Sliver" wafer micro cells in a thin, almost transparent layers that could be used as transparent architectural coverings [14]. Using this technique, two wafers silicon are sufficient to build a 140-watt panel, compared to about 60 wafers needed for conventional modules of same power. However, another way to achieve cost improvements is to reduce waste during crystal formation by improved process modeling, as has FemagSoft, spin-off Catholic University of Leuven. [edit] Thin-film processing of thin film solar cells use less than 1% of the raw material (silicon or other absorbent light) compared to wafer based solar cells, leading to a significant price drop per kWh. There are many research groups around the world actively researching different thin-film approaches and / or materials, however, remains to be seen if these solutions can generate the same space efficiency as traditional silicon processing. One particularly promising technology is crystalline silicon thin films on glass substrates. This technology uses the advantages of crystalline silicon as a material for solar cells, with cost savings of using a thin-film approach. Another interesting aspect of the film thin solar cells is the possibility of depositing the cells in all types of materials, including flexible substrates (PET, for example), which opens a new dimension for new applications. [edit] Polymer Processing The invention of conductive polymers (for which Alan Heeger, Alan MacDiarmid and Hideki Shirakawa were awarded the Nobel prize) may lead to development of much cheaper cells that are based on inexpensive plastics. However, all the solar cells Organic made to date suffer from degradation from exposure to ultraviolet light, and therefore have lifetimes that are too short to be viable. The conjugated double bond systems in the polymers, which carry the load, are always susceptible to breaking when radiated with shorter wavelengths. Furthermore, the most conductive polymers, being highly unsaturated and reactive, are highly sensitive to atmospheric moisture and oxidation, making commercial applications difficult. [edit] nanoparticles nonexperimental processing of silicon solar panels can be made of quantum heterostructures, for example. Carbon nanotubes or quantum dots embedded in conductive polymers and mesoporous metal oxides. By varying the size of quantum dots, the cells can be tuned to absorb different wavelengths. Although research is still in its infancy, quantum dot-modified photovoltaics may be able to high as 42 percent of the efficiency of energy conversion due to multiple exciton generation. [15] [edit] Transparent many drivers of new solar cells use transparent thin films that are also conductors of electrical charge. The key driver in the thin films used research now are transparent conductor oxides (abbreviated "TCO"), and include fluorine-doped tin oxide (SnO2: F, or "organization FTO), doped zinc oxide (eg: ZnO: Al) and indium tin oxide (abbreviated "ito"). These conductive films also used in the LCD industry for flat panel displays. The dual function of a TCO allows light to pass through a substrate window to light active absorbent material underneath, and also serves as an ohmic contact to transport photogenerated charge carriers away from the material to absorb light. The present TCO materials are effective for research, but perhaps are not yet optimized for large-scale photovoltaic production. Conditions are needed very special high-vacuum deposition, can sometimes suffer from poor mechanical strength, and the poor majority of transmission in the infrared part of spectrum (eg: ITO thin films can also be used as infrared filters in the windows of an airplane). These factors make large-scale manufacturing more expensive. A relatively new area has emerged using carbon nanotube networks as a transparent conductor for organic solar cells. Networks of nanotubes are flexible and can be deposited on the surfaces of a variety of ways. With some treatment, nanotube films can be very transparent in the infrared cell, possibly enabling efficient low bandgap solar. Nanotube networks are p-type conductors, whereas traditional transparent conductors are exclusively n-type Availability a p-type transparent conductor could lead to new cell designs that simplify manufacturing and improve

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Energy Crossroads: A burning need to change course, Academic Edition & Public Performance $125.95 This academic version has an extra hour of bonus materials that includes a 25 minutes documentary produced in 1974 soon after the 1973 oil embargo, extended interviews, lesson plans, an Eco-facts sheet, a jpeg file from the poster (11X17) and the 2 mini documentaries from the standard version (Cuba’s Peak Oil and Steve Andrews “Green Home”).Synopsis: As our global population and its appetite for e…