SOLAR CELL PDF

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Solar cells and photodetectors are devices that convert an optical input into current. A solar cell is an example of a photovoltaic device, i.e, a device. Devices exploiting PV effect are called solar cells, also photovoltaic cells or [8 ] ronaldweinland.info Masterpdf ( An Overview of Solar Cell Technology. Mike McGehee. Materials Science and Engineering. Global Climate and Energy Project. Center for Advanced Molecular .


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PDF | A solar cell is an electronic device which directly converts sunlight into electricity. Light shining on the solar cell produces both a current and a voltage to . design of PV solar cells and systems. It is written to address several audiences: engineers and scientists who desire an introduction to the field of photovoltaics. A solar cell, or photovoltaic cell, is an electrical device that converts the energy of light directly "Net Energy Analysis for Sustainable Energy Production from Silicon Based Solar Cells" (PDF). Solar Energy. p. doi/SED

It was featured in an article in the British weekly newspaper The Economist in late Balance of system costs were then higher than those of the panels. The widespread introduction of flat screen televisions in the late s and early s led to the wide availability of large, high-quality glass sheets to cover the panels. During the s, polysilicon "poly" cells became increasingly popular. These cells offer less efficiency than their monosilicon "mono" counterparts, but they are grown in large vats that reduce cost. By the mids, poly was dominant in the low-cost panel market, but more recently the mono returned to widespread use.

The illuminated side of a solar cell generally has a transparent conducting film for allowing light to enter into active material and to collect the generated charge carriers. Typically, films with high transmittance and high electrical conductance such as indium tin oxide , conducting polymers or conducting nanowire networks are used for the purpose.

Semiconductors with band gap between 1 and 1. The efficiency "limit" shown here can be exceeded by multijunction solar cells. Main article: Solar cell efficiency Solar cell efficiency may be broken down into reflectance efficiency, thermodynamic efficiency, charge carrier separation efficiency and conductive efficiency.

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The overall efficiency is the product of these individual metrics. The power conversion efficiency of a solar cell is a parameter which is defined by the fraction of incident power converted into electricity. Due to the difficulty in measuring these parameters directly, other parameters are substituted: thermodynamic efficiency, quantum efficiency , integrated quantum efficiency , VOC ratio, and fill factor.

Reflectance losses are a portion of quantum efficiency under " external quantum efficiency ". Recombination losses make up another portion of quantum efficiency, VOC ratio, and fill factor.

Solar cell

Resistive losses are predominantly categorized under fill factor, but also make up minor portions of quantum efficiency, VOC ratio. The fill factor is the ratio of the actual maximum obtainable power to the product of the open circuit voltage and short circuit current. This is a key parameter in evaluating performance.

Grade B cells were usually between 0. Single p—n junction crystalline silicon devices are now approaching the theoretical limiting power efficiency of Panasonic's was the most efficient. The company moved the front contacts to the rear of the panel, eliminating shaded areas.

In addition they applied thin silicon films to the high quality silicon wafer's front and back to eliminate defects at or near the wafer surface. In addition, the dual-junction device was mechanically stacked with a Si solar cell, to achieve a record one-sun efficiency of The overall efficiency is the product of these individual metrics. The power conversion efficiency of a solar cell is a parameter which is defined by the fraction of incident power converted into electricity.

Due to the difficulty in measuring these parameters directly, other parameters are substituted: thermodynamic efficiency, quantum efficiency , integrated quantum efficiency , VOC ratio, and fill factor. Reflectance losses are a portion of quantum efficiency under " external quantum efficiency ". Recombination losses make up another portion of quantum efficiency, VOC ratio, and fill factor. Resistive losses are predominantly categorized under fill factor, but also make up minor portions of quantum efficiency, VOC ratio.

The fill factor is the ratio of the actual maximum obtainable power to the product of the open circuit voltage and short circuit current. This is a key parameter in evaluating performance.

Grade B cells were usually between 0. Single p—n junction crystalline silicon devices are now approaching the theoretical limiting power efficiency of Panasonic's was the most efficient. The company moved the front contacts to the rear of the panel, eliminating shaded areas. In addition they applied thin silicon films to the high quality silicon wafer's front and back to eliminate defects at or near the wafer surface.

In addition, the dual-junction device was mechanically stacked with a Si solar cell, to achieve a record one-sun efficiency of These materials must have certain characteristics in order to absorb sunlight. Some cells are designed to handle sunlight that reaches the Earth's surface, while others are optimized for use in space. Solar cells can be made of only one single layer of light-absorbing material single-junction or use multiple physical configurations multi-junctions to take advantage of various absorption and charge separation mechanisms.

Solar cells can be classified into first, second and third generation cells. The first generation cells—also called conventional, traditional or wafer -based cells—are made of crystalline silicon , the commercially predominant PV technology, that includes materials such as polysilicon and monocrystalline silicon. Such tariffs encourage the development of solar power projects.

Widespread grid parity , the point at which photovoltaic electricity is equal to or cheaper than grid power without subsidies, likely requires advances on all three fronts. Proponents of solar hope to achieve grid parity first in areas with abundant sun and high electricity costs such as in California and Japan.

George W. Bush set as the date for grid parity in the US. The price of solar panels fell steadily for 40 years, interrupted in when high subsidies in Germany drastically increased demand there and greatly increased the price of purified silicon which is used in computer chips as well as solar panels.

The recession of and the onset of Chinese manufacturing caused prices to resume their decline. The second largest supplier, Canadian Solar Inc. The most commonly known solar cell is configured as a large-area p—n junction made from silicon. Other possible solar cell types are organic solar cells, dye sensitized solar cells, perovskite solar cells, quantum dot solar cells etc.

The illuminated side of a solar cell generally has a transparent conducting film for allowing light to enter into active material and to collect the generated charge carriers. Typically, films with high transmittance and high electrical conductance such as indium tin oxide , conducting polymers or conducting nanowire networks are used for the purpose.

Solar cell efficiency may be broken down into reflectance efficiency, thermodynamic efficiency, charge carrier separation efficiency and conductive efficiency. The overall efficiency is the product of these individual metrics. The power conversion efficiency of a solar cell is a parameter which is defined by the fraction of incident power converted into electricity.

A solar cell has a voltage dependent efficiency curve, temperature coefficients, and allowable shadow angles. Due to the difficulty in measuring these parameters directly, other parameters are substituted: Reflectance losses are a portion of quantum efficiency under " external quantum efficiency ". Recombination losses make up another portion of quantum efficiency, V OC ratio, and fill factor. Resistive losses are predominantly categorized under fill factor, but also make up minor portions of quantum efficiency, V OC ratio.

The fill factor is the ratio of the actual maximum obtainable power to the product of the open circuit voltage and short circuit current. This is a key parameter in evaluating performance. Grade B cells were usually between 0.

Single p—n junction crystalline silicon devices are now approaching the theoretical limiting power efficiency of In , three companies broke the record of Panasonic's was the most efficient.

The company moved the front contacts to the rear of the panel, eliminating shaded areas. In addition they applied thin silicon films to the high quality silicon wafer's front and back to eliminate defects at or near the wafer surface.

For triple-junction thin-film solar cells, the world record is In addition, the dual-junction device was mechanically stacked with a Si solar cell, to achieve a record one-sun efficiency of Solar cells are typically named after the semiconducting material they are made of. These materials must have certain characteristics in order to absorb sunlight. Some cells are designed to handle sunlight that reaches the Earth's surface, while others are optimized for use in space.

Solar cells can be made of only one single layer of light-absorbing material single-junction or use multiple physical configurations multi-junctions to take advantage of various absorption and charge separation mechanisms.

Solar cells can be classified into first, second and third generation cells. The first generation cells—also called conventional, traditional or wafer -based cells—are made of crystalline silicon , the commercially predominant PV technology, that includes materials such as polysilicon and monocrystalline silicon.

Solar Energy Materials & Solar Cells

Second generation cells are thin film solar cells , that include amorphous silicon , CdTe and CIGS cells and are commercially significant in utility-scale photovoltaic power stations , building integrated photovoltaics or in small stand-alone power system. The third generation of solar cells includes a number of thin-film technologies often described as emerging photovoltaics—most of them have not yet been commercially applied and are still in the research or development phase.

Many use organic materials, often organometallic compounds as well as inorganic substances. Despite the fact that their efficiencies had been low and the stability of the absorber material was often too short for commercial applications, there is a lot of research invested into these technologies as they promise to achieve the goal of producing low-cost, high-efficiency solar cells.

By far, the most prevalent bulk material for solar cells is crystalline silicon c-Si , also known as "solar grade silicon". These cells are entirely based around the concept of a p-n junction. Monocrystalline silicon mono-Si solar cells are more efficient and more expensive than most other types of cells.

The corners of the cells look clipped, like an octagon, because the wafer material is cut from cylindrical ingots, that are typically grown by the Czochralski process. Solar panels using mono-Si cells display a distinctive pattern of small white diamonds. Epitaxial wafers of crystalline silicon can be grown on a monocrystalline silicon "seed" wafer by chemical vapor deposition CVD , and then detached as self-supporting wafers of some standard thickness e.

Solar cells made with this " kerfless " technique can have efficiencies approaching those of wafer-cut cells, but at appreciably lower cost if the CVD can be done at atmospheric pressure in a high-throughput inline process.

In June , it was reported that heterojunction solar cells grown epitaxially on n-type monocrystalline silicon wafers had reached an efficiency of Polycrystalline silicon , or multicrystalline silicon multi-Si cells are made from cast square ingots—large blocks of molten silicon carefully cooled and solidified.

They consist of small crystals giving the material its typical metal flake effect. Polysilicon cells are the most common type used in photovoltaics and are less expensive, but also less efficient, than those made from monocrystalline silicon. Ribbon silicon is a type of polycrystalline silicon—it is formed by drawing flat thin films from molten silicon and results in a polycrystalline structure. These cells are cheaper to make than multi-Si, due to a great reduction in silicon waste, as this approach does not require sawing from ingots.

This form was developed in the s and introduced commercially around Also called cast-mono, this design uses polycrystalline casting chambers with small "seeds" of mono material. The result is a bulk mono-like material that is polycrystalline around the outsides. When sliced for processing, the inner sections are high-efficiency mono-like cells but square instead of "clipped" , while the outer edges are sold as conventional poly.

This production method results in mono-like cells at poly-like prices. Thin-film technologies reduce the amount of active material in a cell. Most designs sandwich active material between two panes of glass.

Solar cell - Wikipedia

Since silicon solar panels only use one pane of glass, thin film panels are approximately twice as heavy as crystalline silicon panels, although they have a smaller ecological impact determined from life cycle analysis.

However cadmium is highly toxic and tellurium anion: The cadmium present in the cells would be toxic if released. However, release is impossible during normal operation of the cells and is unlikely during fires in residential roofs. Copper indium gallium selenide CIGS is a direct band gap material.

Traditional methods of fabrication involve vacuum processes including co-evaporation and sputtering. Recent developments at IBM and Nanosolar attempt to lower the cost by using non-vacuum solution processes. Silicon thin-film cells are mainly deposited by chemical vapor deposition typically plasma-enhanced, PE-CVD from silane gas and hydrogen gas. Depending on the deposition parameters, this can yield amorphous silicon a-Si or a-Si: H , protocrystalline silicon or nanocrystalline silicon nc-Si or nc-Si: H , also called microcrystalline silicon.

Amorphous silicon is the most well-developed thin film technology to-date. An amorphous silicon a-Si solar cell is made of non-crystalline or microcrystalline silicon. Amorphous silicon has a higher bandgap 1. The production of a-Si thin film solar cells uses glass as a substrate and deposits a very thin layer of silicon by plasma-enhanced chemical vapor deposition PECVD.

Protocrystalline silicon with a low volume fraction of nanocrystalline silicon is optimal for high open circuit voltage.

The top cell in a-Si absorbs the visible light and leaves the infrared part of the spectrum for the bottom cell in nc-Si. The semiconductor material Gallium arsenide GaAs is also used for single-crystalline thin film solar cells.

Although GaAs cells are very expensive, they hold the world's record in efficiency for a single-junction solar cell at Based on the previous literature and some theoretical analysis, there are several reasons why GaAs has such high power conversion efficiency.

First, GaAs bandgap is 1. Second, because Gallium is a by-product of the smelting of other metals, GaAs cells are relatively insensitive to heat and it can keep high efficiency when temperature is quite high.

Pdf solar cell

Third, GaAs has the wide range of design options. Using GaAs as active layer in solar cell, engineers can have multiple choices of other layers which can better generate electrons and holes in GaAs. Multi-junction cells consist of multiple thin films, each essentially a solar cell grown on top of another, typically using metalorganic vapour phase epitaxy.

Each layer has a different band gap energy to allow it to absorb electromagnetic radiation over a different portion of the spectrum. Multi-junction cells were originally developed for special applications such as satellites and space exploration , but are now used increasingly in terrestrial concentrator photovoltaics CPV , an emerging technology that uses lenses and curved mirrors to concentrate sunlight onto small, highly efficient multi-junction solar cells.

Cell pdf solar

By concentrating sunlight up to a thousand times, High concentrated photovoltaics HCPV has the potential to outcompete conventional solar PV in the future. Tandem solar cells based on monolithic, series connected, gallium indium phosphide GaInP , gallium arsenide GaAs , and germanium Ge p—n junctions, are increasing sales, despite cost pressures. Those materials include gallium 4N, 6N and 7N Ga , arsenic 4N, 6N and 7N and germanium, pyrolitic boron nitride pBN crucibles for growing crystals, and boron oxide, these products are critical to the entire substrate manufacturing industry.

A triple-junction cell, for example, may consist of the semiconductors: In , a new approach was described for producing hybrid photovoltaic wafers combining the high efficiency of III-V multi-junction solar cells with the economies and wealth of experience associated with silicon. The technical complications involved in growing the III-V material on silicon at the required high temperatures, a subject of study for some 30 years, are avoided by epitaxial growth of silicon on GaAs at low temperature by plasma-enhanced chemical vapor deposition PECVD.

A dual-junction solar cell with a band gap of 1. The two cells therefore are separated by a transparent glass slide so the lattice mismatch does not cause strain to the system.

Pdf solar cell

This creates a cell with four electrical contacts and two junctions that demonstrated an efficiency of However, using a GaAs substrate is expensive and not practical. Hence researchers try to make a cell with two electrical contact points and one junction, which does not need a GaAs substrate. This means there will be direct integration of GaInP and Si. Perovskite solar cells are solar cells that include a perovskite -structured material as the active layer.

Most commonly, this is a solution-processed hybrid organic-inorganic tin or lead halide based material. So far most types of perovskite solar cells have not reached sufficient operational stability to be commercialised, although many research groups are investigating ways to solve this. With a transparent rear side, bifacial solar cells can absorb light from both the front and rear sides. Hence, they can produce more electricity than conventional monofacial solar cells.

The first patent of bifacial solar cells was filed by Japanese researcher Hiroshi Mori, in Antonio Luque. Based on US and Spanish patents by Luque, a practical bifacial cell was proposed with a front face as anode and a rear face as cathode; in previously reported proposals and attempts both faces were anodic and interconnection between cells was complicated and expensive.

Due to the reduced manufacturing cost, companies have again started to produce commercial bifacial modules since By , there were at least eight certified PV manufacturers providing bifacial modules in North America. Due to the significant interest in the bifacial technology, a recent study has investigated the performance and optimization of bifacial solar modules worldwide. Sun et al. An online simulation tool is available to model the performance of bifacial modules in any arbitrary location across the entire world.

It can also optimize bifacial modules as a function of tilt angle, azimuth angle, and elevation above the ground. Intermediate band photovoltaics in solar cell research provides methods for exceeding the Shockley—Queisser limit on the efficiency of a cell. It introduces an intermediate band IB energy level in between the valence and conduction bands. Theoretically, introducing an IB allows two photons with energy less than the bandgap to excite an electron from the valence band to the conduction band.

This increases the induced photocurrent and thereby efficiency. Luque and Marti first derived a theoretical limit for an IB device with one midgap energy level using detailed balance. They assumed no carriers were collected at the IB and that the device was under full concentration. They found the maximum efficiency to be In , researchers at California NanoSystems Institute discovered using kesterite and perovskite improved electric power conversion efficiency for solar cells. Photon upconversion is the process of using two low-energy e.

Either of these techniques could be used to produce higher efficiency solar cells by allowing solar photons to be more efficiently used. The difficulty, however, is that the conversion efficiency of existing phosphors exhibiting up- or down-conversion is low, and is typically narrow band. Upconversion process occurs when two infrared photons are absorbed by rare-earth ions to generate a high-energy absorbable photon.

As example, the energy transfer upconversion process ETU , consists in successive transfer processes between excited ions in the near infrared. The upconverter material could be placed below the solar cell to absorb the infrared light that passes through the silicon. Useful ions are most commonly found in the trivalent state. The excited ion emits light above the Si bandgap that is absorbed by the solar cell and creates an additional electron—hole pair that can generate current.

However, the increased efficiency was small. Dye-sensitized solar cells DSSCs are made of low-cost materials and do not need elaborate manufacturing equipment, so they can be made in a DIY fashion.

In bulk it should be significantly less expensive than older solid-state cell designs. Typically a ruthenium metalorganic dye Ru-centered is used as a monolayer of light-absorbing material. The photogenerated electrons from the light absorbing dye are passed on to the n-type TiO 2 and the holes are absorbed by an electrolyte on the other side of the dye.

The circuit is completed by a redox couple in the electrolyte, which can be liquid or solid. This type of cell allows more flexible use of materials and is typically manufactured by screen printing or ultrasonic nozzles , with the potential for lower processing costs than those used for bulk solar cells.

However, the dyes in these cells also suffer from degradation under heat and UV light and the cell casing is difficult to seal due to the solvents used in assembly. Quantum dot solar cells QDSCs are based on the Gratzel cell, or dye-sensitized solar cell architecture, but employ low band gap semiconductor nanoparticles , fabricated with crystallite sizes small enough to form quantum dots such as CdS , CdSe , Sb 2 S 3 , PbS , etc. They also have high extinction coefficients and have shown the possibility of multiple exciton generation.

This TiO 2 layer can then be made photoactive by coating with semiconductor quantum dots using chemical bath deposition , electrophoretic deposition or successive ionic layer adsorption and reaction.

The electrical circuit is then completed through the use of a liquid or solid redox couple. They can be processed from liquid solution, offering the possibility of a simple roll-to-roll printing process, potentially leading to inexpensive, large-scale production. In addition, these cells could be beneficial for some applications where mechanical flexibility and disposability are important.

Current cell efficiencies are, however, very low, and practical devices are essentially non-existent. Energy conversion efficiencies achieved to date using conductive polymers are very low compared to inorganic materials. However, Konarka Power Plastic reached efficiency of 8. The active region of an organic device consists of two materials, one electron donor and one electron acceptor. When a photon is converted into an electron hole pair, typically in the donor material, the charges tend to remain bound in the form of an exciton , separating when the exciton diffuses to the donor-acceptor interface, unlike most other solar cell types.