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A solar cell, or photovoltaic cell, is a semiconductor device consisting of a large-area p-n junction diode, which, in the presence of sunlight is capable of generating usable electrical energy. This conversion is called the photovoltaic effect. The field of research related to solar cells is known as photovoltaics. Derka semiconductor is a material with an electrical conductance that is intermediate between that of an insulator and a conductor. ...
A p-n junction is formed by combining N-type and P-type semiconductors together in very close contact. ...
Jump to: navigation, search Types of diodes A diode can be thought of as the electronic version of a one-way valve. ...
Jump to: navigation, search Prism splitting light Sunlight in the broad sense is the total spectrum of electromagnetic radiation given off by the Sun. ...
The article on electrical energy is located elsewhere. ...
A solar cell, a form of photovoltaic cell, is a device that uses the photoelectric effect to generate electricity from light, thus generating solar power (energy). ...
Solar cells have many applications. They are particularly well suited to, and historically used in situations where electrical power from the grid is unavailable, such as in remote area power systems, Earth orbiting satellites, handheld calculators, remote radiotelephones, water pumping applications, etc. Solar cells (in the form of modules or solar panels) are appearing on building roofs where they are connected through an inverter to the electricity grid in a net metering arrangement. GRID can refer to : GRID computing short for gay-related immune deficiency, a former name for AIDS. See also homosexuality and medical science General Repository for Interaction Datasets, a database of biological interactions hosted at Mount Sinai Hospital in Toronto, Canada This is a disambiguation page — a navigational aid which...
Jump to: navigation, search Earth, also known as the Earth, Terra, and (mostly in the 19th century) Tellus, is the third-closest planet to the Sun. ...
For other uses, please see Satellite (disambiguation) A satellite is an object that orbits another object (known as its primary). ...
This is a list of types of calculators, many of which are obsolete but hoarded by legions of admiring collectors. ...
Jump to: navigation, search Water (from the Old English word wæter; c. ...
Solar Panel made by BP Solar The solar panels (photovoltaic arrays) on this small yacht at sea can charge the 12 V batteries at up to 9 Amps in full, direct sunlight. ...
An inverter is a circuit for converting direct current to alternating current, they are used in a wide range of applications, from small power supplys for a computer to large industrial applications to transport bulk power. ...
Net-metering is a simplified method of metering the energy consumed and produced at a home or business that has its own renewable energy generator, such as a wind turbine. ...
 A solar cell, made from a poly-crystalline silicon wafer found the file on www. ...
found the file on www. ...
Introduction
Etymology The etymology of the term "photovoltaic" comes from the Greek photos meaning light and the name of the Italian physicist Volta, after whom the volt (and consequently voltage) are named. It means literally of light and electricity. Jump to: navigation, search Etymology is the study of the origins of words. ...
Alessandro Giuseppe Antonio Anastasio Volta Alessandro Giuseppe Antonio Anastasio Volta (February 18, 1745 - March 5, 1827) was an Italian physicist known especially for the development of the electric battery. ...
The volt (symbol: V) is the SI derived unit of electric potential difference. ...
This article may be too technical for most readers to understand. ...
History Main article: Timeline of solar cells The Timeline of solar cells begins in the 1800s when it is observed that the presence of sunlight is capable of generating usable electrical energy. ...
The photovoltaic effect was first recognised in 1839 by French physicist Alexandre-Edmond Becquerel. However it was not until 1883 that the first solar cell was built, by Charles Fritts who coated the semiconductor selenium with an extremely thin layer of gold to form the junctions. The device was only around 1% efficient. Russell Ohl is generally recognized for patenting 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. 1839 was a common year starting on Tuesday (see link for calendar). ...
Alexandre_Edmond Becquerel Alexandre_Edmond Becquerel (March 24, 1820 _ May 11, 1891) was a French physicist who studied the solar spectrum, magnetism, electricity, and optics. ...
1883 was a common year starting on Monday (see link for calendar). ...
Derka semiconductor is a material with an electrical conductance that is intermediate between that of an insulator and a conductor. ...
General Name, Symbol, Number selenium, Se, 34 Chemical series nonmetals Group, Period, Block 16, 4, p Appearance gray, metallic luster Atomic mass 78. ...
Jump to: navigation, search General Name, Symbol, Number gold, Au, 79 Chemical series transition metals Group, Period, Block 11, 6, d Appearance metallic yellow Atomic mass 196. ...
Russell Ohl is generally recognized for patenting the modern solar cell (US2402662, Light sensitive device). Ohl was a notable semiconductor researcher prior to the invention of the transistor. ...
Materials and efficiency Various materials are being investigated for solar cells. The two main criteria, efficiency and costs, vary greatly.
Efficiency is the ratio of the electric power output to the light power input. Around noon on a clear day, the solar radiation is approximately 1000 W/m². So a 10% efficient module of 1 square meter than has a power output of 100 W. Solar cell efficiencies vary in between (very low) 6% at amorphous silicon based solar cells, and can reach up to (very high) 30% or even higher efficiencies, using multiple junction research lab cells.
The common method to express economic costs of electricity generating systems, is to calculate a specific price per kilo Watt hour (kWh). The solar cell efficiency in combination with the available irradiation has a major influence on the costs, but generally speaking the overall system efficiency is of importance. To make actual use of the solar generated energy, the electricity is most often fed into the electricity grid using inverters (grid connected PV Systems); in autonomous operating systems batteries are involved to store the electricity that is not needed in the very moment. Using nowadays (2005) commercially available solar cells and system technology, leads to system efficiencies between 5 to 15%. Electricity generation costs have a range from around 50 eurocents/kWh (middle of europe) down to around 25 eurocents/kWh in regions of high solar irradiation.
By far the most common material for solar cells (and all other semiconductor devices) is crystalline silicon. Crystalline silicon solar cells come in three primary categories: General Name, Symbol, Number silicon, Si, 14 Chemical series metalloids Group, Period, Block 14, 3, p Appearance dark gray, bluish tinge Atomic mass 28. ...
- Single crystal or monocrystalline wafers made using the Czochralski process. Most commercial monocrystalline cells have efficiencies on the order of 14%; the SunPower cells have high efficiencies around 20%. Single crystal cells tend to be expensive, and because they are cut from cylindrical ingots, they cannot completely cover a module without a substantial waste of refined silicon. Most monocrystalline panels have uncovered gaps at the corners of four cells. Sunpower and Shell Solar are among the main manufacturers of this type of cells.
- Poly or multi crystalline made from cast ingots - large crucibles of molten silicon carefully cooled and solidified. These cells are cheaper than single crystal cells, but also somewhat less efficient. However, they can easily be formed into square shapes that cover a greater fraction of a panel than monocrystalline cells, and this compensates for their lower efficiencies. See GT Solar HEM Furnace, BP Solar, Sharp Solar and Kyocera Solar.
- Ribbon silicon formed by drawing flat thin films from molten silicon and has a multicrystalline structure. These cells are typically the least efficient, but there is a cost savings since there is very little silicon waste since this approach does not require sawing from ingots. See Evergreen Solar, and RWE Schott Solar.
These technologies are wafer based manufacturing. In other words, in each of the above approaches, self supporting wafers of ~300 micrometres thick are fabricated and then soldered together to form a module. The Czochralski process is a method of crystal growth used to obtain single crystals of semiconductors (e. ...
Royal Dutch Shell plc is a major energy company, one of the top four vertically integrated private sector oil/gas companies in the world (along with BP, ExxonMobil, and Total). ...
Thin film approaches are module based. The entire module substrate is coated with the desired layers and a laser scribe is then used to delineate individual cells. Two main thin film approaches are amorphous silicon and CIS:
- Amorphous silicon films are fabricated using chemical vapor deposition techniques, typically plasma enhanced (PE-CVD). These cells have low efficiencies around 8%.
- CIS stands for general chalcogenide films of Cu(InxGa1-x)(SexS1-x)2. While these films can achieve 11% efficiency, their costs are still too high.
There are additional materials and approaches. For example, Sanyo has pioneered the HIT cell. In this technology, amorphous silicon films are deposited onto crystalline silicon wafers.
The chart below illustrates the various commercial large area module efficiencies and the best laboratory efficiencies obtained for various materials and technologies.
Image:PVModuleLabEffic.jpg
Interconnection and modules Usually, solar cells are electrically connected, and combined into "modules", or solar panels. Solar panels have a sheet of glass on the front, and a resin encapsulation behind to keep the semiconductor wafers safe from the elements (rain, hail, etc). Solar cells are usually connected in series in modules, so that their voltages add. Solar Panel made by BP Solar The solar panels (photovoltaic arrays) on this small yacht at sea can charge the 12 V batteries at up to 9 Amps in full, direct sunlight. ...
See Wafer (cooking) for the original meaning of the word. ...
Rain falling For other uses see Rain (disambiguation). ...
Jump to: navigation, search A large hailstone Hail is a type of graupel (a form of precipitation) composed of spears or irregular lumps of ice. ...
Left: Series / Right: Parallel Arrows indicate direction of current flow. ...
In the physical sciences, potential difference is the difference in potential between two points in a conservative vector field. ...
Theory
Background In order to understand how a solar cell works, a little background theory in semiconductor physics is required. For simplicity, the description here will be limited to describing the workings of single crystalline silicon solar cells. Derka semiconductor is a material with an electrical conductance that is intermediate between that of an insulator and a conductor. ...
Since antiquity, people have tried to understand the behavior of matter: why unsupported objects drop to the ground, why different materials have different properties, and so forth. ...
Silicon is a group 14 (formerly, group IV) atom. This means that each Si atom has 4 valence electrons in its outer shell. Silicon atoms can covalently bond to other silicon atoms to form a solid. There are two basic types of solid silicon, amorphous (having no long range order) and crystalline (where the atoms are arranged in an ordered three dimensional array). There are various other terms for the crystalline structure of silicon; poly-crystalline, micro-crystalline, nano-crystalline etc, and these refer to the size of the crystal "grains" which make up the solid. Solar cells can be, and are made from each of these types of silicon, the most common being poly-crystalline. The carbon group is group 14 (IUPAC style) in the periodic table. ...
Jump to: navigation, search Properties For alternative meanings see atom (disambiguation). ...
Properties The electron (also called negatron, commonly represented as e−) is a subatomic particle. ...
Electron atomic and molecular orbitals In quantum mechanics, the states of an atom, i. ...
Covalent bonding is a form of chemical bonding characterized by the sharing of one or more pairs of electrons between atoms, in order to produce a mutual attraction, which holds the resultant molecule together. ...
In jewelry, a solid gold piece is the alternative to gold-filled or gold-plated jewelry. ...
An amorphous solid is a solid in which there is no long-range order of the positions of the atoms. ...
Crystal (disambiguation) Insulin crystals A crystal is a solid in which the constituent atoms, molecules, or ions are packed in a regularly ordered, repeating pattern extending in all three spatial dimensions. ...
An assortment of grains The word grain has a great many meanings, most being descriptive of a small piece or particle. ...
Silicon is a semiconductor. This means that in solid silicon, there are certain bands of energies which the electrons are allowed to have, and other energies between these bands which are forbidden. These forbidden energies are called the "band gap". The allowed and forbidden bands of energy are explained by the theory of quantum mechanics. In solid state physics and related applied fields, the band gap is the energy difference between the top of the valence band and the bottom of the conduction band in insulators and semiconductors. ...
Jump to: navigation, search Fig. ...
At room temperature, pure silicon is a poor electrical conductor. In quantum mechanics, this is explained by the fact that the Fermi level lies in the forbidden band-gap. To make silicon a better conductor, it is "doped" with very small amounts of atoms from either group 13 (III) or group 15 (V) of the periodic table. These "dopant" atoms take the place of the silicon atoms in the crystal lattice, and bond with their neighbouring Si atoms in almost the same way as other Si atoms do. However, because group 13 atoms have only 3 valence electrons, and group 15 atoms have 5 valence electrons, there is either one too few, or one too many electrons to satisfy the four covalent bonds around each atom. Since these extra electrons, or lack of electrons (known as "holes") are not involved in the covalent bonds of the crystal lattice, they are free to move around within the solid. Silicon which is doped with group 13 atoms (aluminium, gallium) is known as p-type silicon because the majority charge carriers (holes) carry a positive charge, whilst silicon doped with group 15 atoms (phosphorus, arsenic) is known as n-type silicon because the majority charge carriers (electrons) are negative. It should be noted that both n-type and p-type silcion are electrically neutral, i.e. they have the same numbers of positive and negative charges, it is just that in n-type silicon, some of the negative charges are free to move around, while the converse is true for p-type silicon. It has been suggested that Conductor (power engineering) be merged into this article or section. ...
In quantum mechanics, particles with a half-integer spin, usually spin 1/2 (for example electrons) follow the Pauli exclusion principle, which states that no two particles may occupy the same quantum state. ...
In semiconductor production, doping refers to the process of intentionally introducing impurities into an intrinsic semiconductor in order to change its electrical properties. ...
The Boron group is periodic table group 13 (IUPAC style) in the periodic table. ...
The group 15 elements(a. ...
Jump to: navigation, search The periodic table of the chemical elements, also called the Mendeleev periodic table, is a tabular display of the known chemical elements. ...
In solid state physics, an electron hole (usually referred to simply as a hole) is the absence of an electron from the otherwise full valence band. ...
Jump to: navigation, search General Name, Symbol, Number aluminium, Al, 13 Chemical series poor metals Group, Period, Block 13, 3, p Appearance silvery Atomic mass 26. ...
General Name, Symbol, Number gallium, Ga, 31 Chemical series poor metals Group, Period, Block 13, 4, p Appearance silvery white Atomic mass 69. ...
A P-type semiconductor is obtained by carrying out a process of doping, that is adding a certain type of atoms to the semiconductor in order to increase the number of free (in this case positive) charges. ...
Jump to: navigation, search This article is about the chemical element. ...
General Name, Symbol, Number arsenic, As, 33 Chemical series metalloids Group, Period, Block 15, 4, p Appearance metallic gray Atomic mass 74. ...
An N-type semiconductor is obtained by carrying out a process of doping, that is adding a certain type of atoms to the semiconductor in order to increase the number of free (in this case negative) charge carriers. ...
Light generation of carriers
 The absorption of photons creates electron-hole pairs, which diffuse to the electrical contacts and can be extracted to power electrical devices When a photon of light hits a piece of silicon, one of two things can happen. The first is that the photon can pass straight through the silicon. This (generally) happens when the energy of the photon is lower than the bandgap energy of the silicon semiconductor. The second thing that can happen is that the photon is absorbed by the silicon. This (generally) happens if the photon energy is greater than the bandgap energy of silicon. When a photon is absorbed, its energy is given to an electron in the crystal lattice. Usually this electron is in the valence band, and is tightly bound in covalent bonds between neighbouring atoms, and hence unable to move far. The energy given to it by the photon "excites" it into the conduction band, where it is free to move around 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 the bonded electrons of neighboring atoms to move into the "hole," leaving another hole behind, and in this way a hole can move through the lattice. Thus, it can be said that photons absorbed in the semiconductor create mobile electron-hole pairs. The photovoltaic cell (PV cell) offers a limitless and environmentally friendly source of electricity. ...
The photovoltaic cell (PV cell) offers a limitless and environmentally friendly source of electricity. ...
For the Science Fiction weapon, as seen in Star Trek, see Photon torpedo. ...
Prism splitting light Light is electromagnetic radiation with a wavelength that is visible to the eye (visible light) or, in a technical or scientific setting, electromagnetic radiation of any wavelength. ...
In solids, the valence band is the highest range of electron energies where electrons are normally present at zero temperature. ...
In semiconductors and insulators, the conduction band is the range of electron energy, higher than that of the valence band, sufficient to make the electrons free to accelerate under the influence of an applied electric field and thus constitute an electric current. ...
A photon only needs to have energy greater than the band gap energy to excite an electron from the valence band into the conduction band. However, the solar frequency spectrum approximates a black body spectrum at ~6000 K, and as such, much of the solar radiation reaching the Earth is composed of photons with energies greater than the band gap of silicon. These higher energy photons will be absorbed by the solar cell, but the difference in energy between these photons and the silicon band gap is converted into heat (via lattice vibrations - called phonons) rather than into usable electrical energy. In mathematics, physics and signal processing, the frequency spectrum is a representation of a signal or other function in terms of frequency (in the frequency domain). It is the projection of the function onto a set of sinusoidal basis functions. ...
As the temperature decreases, the peak of the black body radiation curve moves to lower intensities and longer wavelengths. ...
Jump to: navigation, search Earth, also known as the Earth, Terra, and (mostly in the 19th century) Tellus, is the third-closest planet to the Sun. ...
A phonon is a quantized mode of vibration occurring in a rigid crystal lattice, such as the atomic lattice of a solid. ...
The p-n junction A solar cell is a large-area semiconductor p-n junction. To understand the workings of a p-n junction it is convenient to imagine what happens when a piece of n-type silicon is brought into contact with a piece of p-type silicon. In practice, however, the p-n junctions of solar cells are not made in this way, but rather, usually, by diffusing an n-type dopant into one side of a p-type wafer. A p-n junction is formed by combining N-type and P-type semiconductors together in very close contact. ...
If we imagine what happens when a piece of p-type silicon is placed in intimate contact with a piece of n-type silicon, then what occurs is a diffusion of electrons from the region of high electron concentration - the n-type side of the junction, into the region of low electron concentration - p-type side of the junction. When the electrons diffuse across the p-n junction, they recombine with holes on the p-type side. This diffusion of carriers does not happen indefinitely however, because of the electric field which is created by the imbalance of charge immediately either side of the junction which this diffusion creates. Electrons from donor atoms on the n-type side of the junction are crossing into the p-type side, leaving behind the (extra) positively charged nuclei of the group 15 donor atoms, leaving an excess of positive charge on the n-type side of the junction. At the same time, these electrons are filling in holes on the p-type side of the junction, becoming involved in covalent bonds around the group 13 acceptor atoms, making an excess of negative charge on the p-type side of the junction. This imbalance of charge across the p-n junction sets up an electric field which opposes further diffusion of charge carriers across the junction. Diffusion, being the spontaneous spreading of matter (particles), heat, or momentum, is one type of transport phenomena. ...
In physics, an electric field or E-field is an effect produced by an electric charge that exerts a force on charged objects in its vicinity. ...
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". In semiconductor physics, the Depletion Zone or Depletion layer is a nonconductive region within a conductive, doped semiconductor material where the charge carriers have been swept away. ...
The electric field which is set up across the p-n junction creates a diode, allowing current to flow in only one direction across the junction. Electrons may pass from the n-type side into the p-type side, and holes may pass from the p-type side to the n-type side. But since the sign of the charge on electrons and holes is opposite, conventional current may only flow in one direction. Jump to: navigation, search Types of diodes A diode can be thought of as the electronic version of a one-way valve. ...
Jump to: navigation, search In electricity, current refers to electric current, which is the flow of electrons. ...
In electricity, current is the rate of flow of charges, usually through a metal wire or some other electrical conductor. ...
Separation of carriers by the p-n junction Once the electron-hole pair has been created by the absorption of a photon, the electron and hole are both free to move off independently within the silicon lattice. If they are created within a minority carrier diffusion length of the junction, then, depending on which side of the junction the electron-hole pair is created, the electric field at the junction will either sweep the electron to the n-type side, or the hole to the p-type side.
Connection to an external load Ohmic metal-semiconductor contacts are made to both the n-type and p-type sides of the solar cell, and the electrodes connected to an external load. Electrons that are created on the n-type side, or have been "collected" by the junction and swept onto the n-type side, may travel through the wire, power the load, and continue through the wire until they reach the p-type semiconductor-metal contact. Here, they recombine with a hole that was either created as an electron-hole pair on the p-type side of the solar cell, or swept across the junction from the n-type side after being created there. Hot metal work from a blacksmith In chemistry, a metal (Greek: Metallon) is an element that readily forms ions (cations) and has metallic bonds, and metals are sometimes described as a lattice of positive ions (cations) in a cloud of electrons. ...
Equivalent circuit of a solar cell
 The equivalent circuit of a solar cell
 The schematic symbol of a solar cell To understand the electronic behaviour of a solar cell, it is useful to create a model which is electrically equivalent, and is based on discrete electrical components whose behaviour is well known. An ideal solar cell may be modelled by a current source in parallel with a diode. In practice no solar cell is ideal, so a shunt resistance and a series resistance component are 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 of a solar cell for use in circuit diagrams. Download high resolution version (792x612, 18 KB)I created this file myself with xcircuit software File links The following pages link to this file: Solar cell Categories: GFDL images ...
Download high resolution version (792x612, 18 KB)I created this file myself with xcircuit software File links The following pages link to this file: Solar cell Categories: GFDL images ...
Schematic symbol for a photovoltaic cell. ...
Schematic symbol for a photovoltaic cell. ...
Model has many different meanings, depending on the context. ...
Manufacture and devices Because solar cells are semiconductor devices, they share many of the same processing and manufacturing techniques as other semiconductor devices such as computer and memory chips. However, the stringent requirements for cleanliness and quality control of semiconductor fabrication are a little more relaxed for solar cells. Jump to: navigation, search A computer is a device or machine for processing information from data according to a program — a compiled list of instructions. ...
Jump to: navigation, search This article needs to be cleaned up to conform to a higher standard of quality. ...
Jump to: navigation, search Optical Microscope image of an integrated circuit showing defects in the aluminium layer deposition. ...
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 be made in to excellent high efficiency solar cells, but they are generally considered to be too expensive for large-scale mass production.
Poly-crystalline silicon wafers are made by wire-sawing block-cast silicon ingots into very thin (250 to 350 micrometre) slices or wafers. The wafers are usually lightly p-type doped.
To make a solar cell from the wafer, an n-type diffusion is performed on the front side of the wafer, forming a p-n junction a few hundred nanometres below the surface.
Antireflection coatings, which increase the amount of light coupled into the solar cell, are typically applied next. Over the past decade, silicon nitride has gradually replaced titanium dioxide as the antireflection coating of choice because of its excellent surface passivation qualities (i.e., it prevents carrier recombination at the surface of the solar cell). It is typically applied in a layer several hundred nanometers thick using plasma-enhanced chemical vapor deposition (PECVD).
The wafer is then metallised, whereby a full area metal contact is made on the back surface, and a grid-like metal contact made up of fine "fingers" and larger "busbars" is screen-printed onto the front surface using a silver paste. The rear contact is also formed by screen-printing a metal paste, typically aluminum. Usually this contact covers the entire rear side of the cell, though in some cell designs it is printed in a grid pattern. The metal electrodes will then require some kind of heat treatment or "sintering" to make Ohmic contact with the silicon. Jump to: navigation, search General Name, Symbol, Number silver, Ag, 47 Chemical series transition metals Group, Period, Block 11, 5, d Appearance lustrous white metal Atomic mass 107. ...
After the metal contacts are made, the solar cells are interconnected in series (and/or parallel) by flat wires or metal ribbons, and assembled into modules or "solar panels". Solar panels have a sheet of tempered glass on the front, and a polymer encapsulation on the back. The materials definition of a glass is a uniform amorphous solid material, usually produced when a suitably viscous molten material cools very rapidly, thereby not giving enough time for a regular crystal lattice to form. ...
Jump to: navigation, search A polymer is a generic term used to describe a substantially long molecule. ...
Some solar cells have textured front surfaces that, like antireflection coatings, serve to increase the amount of light coupled into the cell. Such surfaces can usually only be formed on single-crystal silicon, though in recent years methods of forming them on multicrystalline silicon have been developed.
Energy conversion efficiency Typical module efficiencies for commercially available screen printed multicrystalline solar cells are around 12%. A solar module's energy conversion efficiency, (or just efficiency) is the ratio of the maximum output electrical power divided by the input light power under "standard" test conditions. The "standard" solar radiation (known as the "air mass 1.5 spectrum") has a power density of 1000 watts per square metre. Thus, a typical 1 m² solar panel in direct sunlight will produce approximately 120 watts of peak power. A more technical description of efficiency is the maximum power, made up of the fill factor x the open circuit voltage x the short circuit current, divided by the input power. This is a disambiguation page — a navigational aid which lists other pages that might otherwise share the same title. ...
The metre, or meter (symbol: m) is the SI base unit of length. ...
The fill factor is defined as the ratio of the maximum power (Vmp x Jmp) divided by the short-circuit current (Isc) and open-circuit voltage (Voc) in light current density - voltage (J-V) characteristics of solar cells. ...
This article may be too technical for most readers to understand. ...
Jump to: navigation, search In electricity, current refers to electric current, which is the flow of electrons. ...
Applications and implementations See the article solar panel for information about applications and implementations of solar cells and panels. Solar Panel (photovoltaic array) A laundromat in California powered by solar panels on the roof. ...
Cost analysis The US retail module costs are in the $3.50 to $5.00/Wp range (see SolarBuzz). Additional installation costs for a residential rooftop retrofit in California (CA) is around $3.50/Wp or more. So on the low side, installed system costs are about $7.00/Wp in CA, and probably higher in places with less experience. Federal, state, utility, and other subsidies combined pay about half the cost. So CA rule of thumb is that the installed system PV will cost you at the low end, $3.50/Wp. Wikiquote has a collection of quotations by or about: United States Wikinews has news related to this article: United States United States government CIA World Factbook Entry for United States House. ...
The United States dollar, or American dollar, is the official currency of the United States. ...
State nickname: The Golden State Other U.S. States Capital Sacramento Largest city Los Angeles Governor Arnold Schwarzenegger (R) Senators Dianne Feinstein (D) Barbara Boxer (D) Official languages English Area 410,000 km² (3rd) - Land 404,298 km² - Water 20,047 km² (4. ...
A subsidy is generally a monetary grant given by government in support of an activity regarded as being in the public interest. ...
Under net metering, one offsets regular retail utility rate which for CA is about 11 cents/kWh. Knowing installed system costs, amount of sunshine, and the utility rates, one can figure out the years till payback with or without financing costs. Assuming no financing costs and a $6/Wp installed system cost (lower than current $7), one can take sunshine and utility rate information from around the globe and come up with a payback graph such as shown below. The addition of subsidies brings down the years to payback proportionately. For example, if the years to payback were 24 years at $6/Wp, and subsidies brought that down to $3/Wp, the years to payback would be 12.
 Years till PV system payback under net metering and no financing or subsidies. ...
Current research There are currently many research groups active in the field of photovoltaics at universities and research institutions around the world. Jump to: navigation, search Research is an active, diligent, and systematic process of inquiry in order to discover, interpret or revise facts, events, behaviours, or theories, or to make practical applications with the help of such facts, laws, or theories. ...
A solar cell, a form of photovoltaic cell, is a device that uses the photoelectric effect to generate electricity from light, thus generating solar power (energy). ...
A university is an institution of higher education and of research, which grants academic degrees. ...
Much of the research is focussed on making solar cells cheaper and/or more efficient, so that they can more effectively compete with other energy sources, including fossil energy. One way of doing this is to develop cheaper methods of obtaining silicon that is sufficiently pure. Silicon is a very common element, but is normally bound in silica sand. Another approach is to significantly reduce the amount of raw material used in the manufacture of solar cells. The various thin-film technologies currently being developed make use of this approach to reducing the cost of electricity from solar cells. Fossil fuels are hydrocarbon-containing natural resources such as coal, petroleum and natural gas. ...
Patterns in the sand Sand is an example of a class of materials called granular matter. ...
The invention of conductive polymers, (for which Alan Heeger was awarded a Nobel prize) may lead to the development of much cheaper cells that are based on inexpensive plastics, rather than semiconductor grade silicon. However, all organic solar cells made to date suffer from degradation upon exposure to UV light, and hence have lifetimes which are far too short to be viable. Jump to: navigation, search Conductive polymers are organic polymer semiconductors. ...
Alan J. Heeger (born 22 January 1936 in Sioux City, Iowa) is a United States chemistry and physicsacademic and nobel prize winner. ...
Sir Edward Appletons medal Photographs of Nobel Prize Medals. ...
Note: Ultraviolet is also the name of a 1998 UK television miniseries about vampires. ...
Thin-film solar cells The next step in reducing the cost of solar cells and panels seems certain to come from thin-film technology. Thin-film solar cells use less than 1% of the raw material (silicon) 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.
Thin Film solar cells are mainly deposited by PECVD from silane gas and hydrogen. This process produces a material without crystalline orientation : amorphous silicon. Depending on the deposition's parameters both protocrystalline silicon, which has been shown to exhibit the most stability, and nanocrystalline silicon can also be obtained. These types of silicon present dandling and twisted bonds, which results in the aparition of deep defects (energy levels in the bandgap) as well as in the deformation of the valence and conduction bands (band tails). This contributes to reduce the efficiency of Thin-Film solar cells by reducing the number of collected electron-hole pair by incident photon. DC plasma (violet) enhances the growth of carbon nanotubes in this laboratory-scale PECVD apparatus. ...
Silane is a chemical compound with chemical formula SiH4. ...
Jump to: navigation, search General Name, Symbol, Number hydrogen, H, 1 Chemical series nonmetals Group, Period, Block 1, 1, s Appearance colorless Atomic mass 1. ...
Amorphous silicon (a-Si) is the non-crystalline allotropic form of silicon. ...
// Protocrystalline or Protocrystallinity Deposition phase diagrams developed by real time spectroscopic ellipsometry have led to the concept of the protocrystalline hydrogenated silicon (Si:H) growth regime, shaded in yellow in the figure below. ...
Nanocrystalline silicon (nc-Si) is similar to amorphous silicon (a-Si), in that it has an amorphous phase. ...
A graph showing variation of quantum efficiency with wavelength of the CCD chips in the Hubble Space Telescopes Wide Field and Planetary Camera 2. ...
Amorphous silicon (a-Si) has a higher bandgap (1.7 eV) than crystalline Silicon (c-Si) (1.1 eV), which means it is more efficient to absorb the visible part of the solar spectrum, but it fails to collect an important part of the spectrum : the infrared. As nano crystalline Si has about the same bandgap as c-Si, the two material can be combined by depositing two diodes on top of each other : the tandem cell. The top cell in a-Si absorbs the visible light and leaves the infrared part of the spectrum for the bottom cell in nanocrystalline Si. Jump to: navigation, search Image of a small dog taken in mid-infrared (thermal) light (false color) Infrared (IR) radiation is electromagnetic radiation of a wavelength longer than visible light, but shorter than microwave radiation. ...
One particularly promising technology is crystalline silicon thin-films on glass substrates. This technology makes use of the advantages of crystalline silicon as a solar cell material, with the cost savings of using a thin-film approach. From the Pacific Solar website:
- "Crystalline Silicon on Glass (CSG) [is] the photovoltaic technology developed by Pacific Solar that is now being commercialised by CSG Solar. A very thin layer of silicon, less than two micrometres thick, is deposited directly onto a glass sheet whose surface has been roughened by applying a layer of tiny glass beads. The silicon is not crystalline when first deposited, but becomes so after heat treatment in an oven. The resulting layer is processed using lasers and ink-jet printing techniques to form the electrical contacts needed to get the solar-produced electricity out of the thin silicon film."
In 2005, a full-scale production factory is being built in Thalheim, Germany to commercialise this technology (project management by IB Vogt GmbH). CSG Solar expects to release its first product for sale in 2006. Each solar module will have a rated power exceeding 100 watts and will be cheaper than competing solar panels. IB Vogt GmbH is a German engineering company specialized in design and construction of high-tech solar cell and thin film production facilities. ...
Another interesting aspect of thin-film solar cells is the possibility to deposit the cells on all kind of materials, including flexible substrates (PET for example), which opens a new dimension for new applications. A picture of a man with a domesticated dog A pet is an animal that is kept by humans for companionship and enjoyment, as opposed to livestock, which are kept for economic reasons. ...
Exotic materials For special applications, such as Deep Space 1, high-efficiency cells can be made from gallium arsenide by molecular beam epitaxy. Such cells have many diodes in series, each with a different band gap energy so that it absorbs its share of the electromagnetic spectrum with very high efficiency. Triple junction solar cell have (as the name suggest) 3 diodes layered on top of each other, each absorbing a different spectrum of light, efficiency as high as 28% have been achieved. The multiple junction solar cells may be very efficient, but are prohibitively expensive to make. Cost-effective use of these cells could be achieved with concentrating optics so that less of the array consists of actual semiconductor devices. The spacecraft Deep Space 1 was launched October 24, 1998 on top of a Delta rocket. ...
This article is about the chemical compound. ...
Molecular beam epitaxy, abbreviated MBE, is the deposition of one or more pure materials onto a single crystal wafer, one layer of atoms at a time, under ultra-high vacuum, forming a perfect crystal. ...
In solid state physics and related applied fields, the band gap is the energy difference between the top of the valence band and the bottom of the conduction band in insulators and semiconductors. ...
Experimental non-silicon solar panels can be made of carbon nanotubes or quantum dots embedded in a special plastic. These have only one-tenth the efficiency of silicon panels but could be manufactured in ordinary factories, not clean rooms which should lower the cost. While conventional solar cells only generate electricity from the visible light spectrum, experimental cells have been made that use the infrared spectrum. By varying the size of the quantum dots, the cells can be tuned to absorb different wavelengths. If panels that absorb both visible and infrared spectrums are able to be manufactured, the panels may be able to achieve up to 30 percent efficiency. (McDonald, et al., 2005) Jump to: navigation, search An electronic device known as a diode can be formed by joining two nanoscale carbon tubes with different electronic properties. ...
A Quantum Dot, also called a semiconductor nanocrytal, is a semiconductor crystal whose size is on the order of a few nanometers to a few hundred nanometers. ...
Jump to: navigation, search Conductive polymers are organic polymer semiconductors. ...
Jump to: navigation, search Image of a small dog taken in mid-infrared (thermal) light (false color) Infrared (IR) radiation is electromagnetic radiation of a wavelength longer than visible light, but shorter than microwave radiation. ...
Some of the most efficient solar cell materials are cadmium telluride (CdTe) and copper indium gallium selenide (CIGS). Unlike the basic silicon solar cell, which can be modelled as a simple p-n junction (see under semiconductor), these cells are best described by a more complex heterojunction model. The best efficiency of a bare solar cell as of April 2003 was 16.5% [Dr IM Dharmadasa, Sheffield Hallam University, UK]. Higher efficiencies (around 30%) can be obtained by using optics to concentrate the incident light. General Name, Symbol, Number cadmium, Cd, 48 Chemical series transition metals Group, Period, Block 12, 5, d Appearance silvery gray metallic Atomic mass 112. ...
General Name, Symbol, Number tellurium, Te, 52 Chemical series metalloids Group, Period, Block 16, 5, p Appearance silvery lustrous gray Atomic mass 127. ...
General Name, Symbol, Number copper, Cu, 29 Chemical series transition metals Group, Period, Block 11, 4, d Appearance metallic brown Atomic mass 63. ...
General Name, Symbol, Number indium, In, 49 Chemical series poor metals Group, Period, Block 13, 5, p Appearance silvery lustrous gray Atomic mass 114. ...
General Name, Symbol, Number gallium, Ga, 31 Chemical series poor metals Group, Period, Block 13, 4, p Appearance silvery white Atomic mass 69. ...
General Name, Symbol, Number selenium, Se, 34 Chemical series nonmetals Group, Period, Block 16, 4, p Appearance gray, metallic luster Atomic mass 78. ...
Derka semiconductor is a material with an electrical conductance that is intermediate between that of an insulator and a conductor. ...
Jump to: navigation, search 2003(MMIII) is a common year starting on Wednesday of the Gregorian calendar. ...
Polymer or organic solar cells are built from ultra thin layers (typically 100 nm) of organic semiconductors such as polyphenylene vinylene and fullerene. The p/n junction model is only a crude description of the functioning of such cells, as electron hopping and other processes also play a crucial role. They are potentially cheaper to manufacture than silicon or inorganic cells, but efficiencies achieved to date are low and cells are highly sensitive to air and moisture, making commercial applications difficult. In the reverse mode, the technology has however already successfully been commercialised in organic LEDs and organic displays, also called polymer displays. Jump to: navigation, search A polymer is a generic term used to describe a substantially long molecule. ...
Organic has several meanings and related topics. ...
Fullerene C540 Fullerenes are one of only four types of naturally occurring forms of carbon (the other three being diamond, graphite and ceraphite). ...
Properties The electron is a fundamental subatomic particle which carries a negative electric charge. ...
Various light-emitting diodes (5 mm reds, 3 mm greens and yellows) A light-emitting diode (LED) is a semiconductor device that emits incoherent monochromatic light when electrically biased in the forward direction. ...
Graetzel cells (sometimes called photoelectrochemical cells) have been around for two decades or so. A p/n junction is used here too in the form of a doped solid (normally titanium dioxide) in contact with a solid or liquid electrolyte (for example CuI). In contrast to the classical solar cell not the semiconductor but a dye placed at the p/n interface is used for absorption of radiation, mimicking the process of photosynthesis. As a result, this type of cell allows a more flexible use of materials. Like organic solar cells, Graetzel cells can be manufactured under "dirty" conditions. Commercial applications have failed to appear due to the fast degradation occurring in Graetzel cells. A photoelectrochemical cell uses electromagnetic radiation including visible light to produce hydrogen, in a similar way to electrolysis of water. ...
A photoelectrochemical cell uses electromagnetic radiation including visible light to produce hydrogen, in a similar way to electrolysis of water. ...
Titanium dioxide, also known as titanium(IV) oxide or titania, is the naturally occurring oxide of titanium, chemical formula TiO2. ...
Jump to: navigation, search Yarn drying after being dyed in the early American tradition, at Conner Prairie living history museum. ...
Jump to: navigation, search [[Image:is an important biochemical process in which plants, algae, and some bacteria harness the energy of sunlight to produce food. ...
Solar cells and energy payback There is a common but mistaken notion that solar cells never produce more energy than it takes to make them. While the expected working lifetime is around 40 years, the energy payback time of a solar panel is anywhere from 1 to 30 years (usually under five) depending on the type and where it is used (see net energy gain). This means solar cells are net energy producers and can "reproduce" themselves (from 6 to more than 30 times) over their lifetime. For details see Net Energy Analysis For Sustainable Energy Production From Silicon Based Solar Cells. Net Energy Gain is an important concept in energy economics, referring to the difference between the energy required to harvest the energy source against the energy provided by using that source. ...
See also Jump to: navigation, search An autonomous building is a building designed to be operated independently from infrastructual support services such as the electric power power grid, municipal water systems, sewage treatment systems, storm drains, communication services, and (in some cases) public roads. ...
Energy development is the ongoing effort to provide abundant and accessible energy, through knowledge, skills and constructions. ...
Green technology is a technology that offers a more environmentally friendly solution compared to an existing technology. ...
A photodiode is an electronic component and a type of photodetector. ...
A photovore robot is one that seeks light. ...
Jump to: navigation, search Renewable energy (sources) or RES capture their energy from existing flows of energy, from on-going natural processes, such as sunshine, wind, flowing water, biological processes, and geothermal heat flows. ...
Solar power describes a number of methods of harnessing energy from the light of the sun. ...
Solar Panel (photovoltaic array) A laundromat in California powered by solar panels on the roof. ...
Timeline of solar energy 1767 Horace de Saussure develops a solar oven. ...
References - McDonald SA, Konstantatos G, Zhang S, Cyr PW, Klem EJ, Levina L, Sargent EH (2005). Solution-processed PbS quantum dot infrared photodetectors and photovoltaics. Nature Materials 4 (2): 138-42. PMID 15640806
External links - Use of solar cells in Kenya and Uganda, in Africa
- Pennicott, Katie, "Solar cell edges towards endless energy". 7 December 2001. PhysicsWeb.
- Dye Sensitized Solar Cells (DYSC) based on Nanocrystalline Oxide Semiconductor Films
- News searching: Solar Cell, Photovoltaic
- Historical: Photovoltaic Solar Energy Conversion: An Update
- Wladek Walukiewicz, Materials Sciences Division, Berkeley Lab.: Full Solar Spectrum Photovoltaic Materials Identified. Quote: "... Maximum, theoretically predicted efficiencies increase to 50%, 56%, and 72% for stacks of 2, 3, and 36 junctions with appropriately optimized energy gaps, respectively...."
- CNET: SunPower Announces World's Most Efficient, Low-Cost Silicon Solar Cell (12 May 2003) Quote: "...The National Renewable Energy Laboratory (NREL) has verified 20.4 percent conversion efficiency for the A-300...."
- SunPower A-300 (pdf), SunPower
- Scientists Create New Solar Cell (29 March 2002) Quote: "...semiconducting plastic material known as P3HT... 1.7 percent for sunlight..."
- 'Denim' solar panels to clothe future buildings (15 February 2003) Quote: "... Unlike conventional solar cells, the new, cheap material has no rigid silicon base..."
- Residential Solar Power Systems - Photo Gallery
- Examples of Photovoltaic Systems
- howstuffworks.com: How Solar Cells Work
- azonano.com: Carbon Nanotube Structures Could Provide More Efficient Solar Power for Soldiers (28 February 2005)
- Solar energy timeline
// Etymology World map showing Africa (geographically) The name Africa came into Western use through the Romans, who used the name Africa terra — land of the Afri (plural, or Afer singular) — for the northern part of the continent, as the province of Africa with its capital Carthage, corresponding to modern-day...
December 7 is the 341st day (342nd on leap years) of the year in the Gregorian calendar. ...
Jump to: navigation, search 2001: A Space Odyssey. ...
Jump to: navigation, search May 12 is the 132nd day of the year in the Gregorian Calendar (133rd in leap years). ...
Jump to: navigation, search 2003(MMIII) is a common year starting on Wednesday of the Gregorian calendar. ...
March 29 is the 88th day of the year in the Gregorian Calendar (89th in Leap years). ...
Jump to: navigation, search 2002(MMII) is a common year starting on Tuesday of the Gregorian calendar. ...
February 15 is the 46th day of the year in the Gregorian Calendar. ...
Jump to: navigation, search 2003(MMIII) is a common year starting on Wednesday of the Gregorian calendar. ...
February 28 is the 59th day of the year in the Gregorian calendar. ...
Jump to: navigation, search 2005(MMV) is a common year starting on Saturday of the Gregorian calendar. ...
Yield data
Theory - National Renewable Energy Laboratory (NREL): Photovoltaics for Buildings: PV Technology for the Home Factsheets
- 1993, National Renewable Energy Laboratory (NREL): Photovoltaics: Unlimited Electrical Energy From the Sun BrokenLink
- Electrical models of solar cells
Cost Benefit - PVWATTS - A Performance Calculator for Grid-Connected PV Systems
Do-it-yourself - PEC (Photo Electro Chromic)
- How to Build Your Own Solar Cell
- DIY (Do It Yourself): Nanocrystalline Dye-Sensitized Solar Cell Kit Quote: "... sunlight-to-electrical energy conversion efficiency is between 1 and 0.5 %..."
- Cuprous oxide solar cells
- Make a solar cell in your kitchen, A flat panel solar battery
- From: How to Build a Solar Cell That Really Works by Walt Noon
Indexes The Open Directory Project (ODP), also known as DMoz (for Directory. ...
Newsgroups
Patents - US2402662 -- Light sensitive device -- R. S. Ohl
- US1289369 -- Method of increasing the capacity of photosensitive electrical cells
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