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The design of the PECVD system has great impact on the production cost of such panel, therefore most equipment suppliers put their focus on the design of PECVD for higher throughput, that leads to lower manufacturing cost[4] particularly when thesilane is recycled.[5]

Amorphous silicon has become the material of choice for the active layer in thin-film transistors (TFTs), which are most widely used in large-area electronicsapplications, mainly for liquid-crystal displays (LCDs). HP Pavilion dv7-1003eo CPU Fan

a-Si has been used as a photovoltaic solar cell material for devices which require very little power, such as pocket calculators, because their lower performance compared to traditional c-Si solar cells is more than offset by their simplified and lower cost of deposition onto a substrate.

More recently, improvements in a-Si construction techniques have made them more attractive for large-area solar cell use as well. Dell Vostro 3450 CPU Fan

Here their lower inherent efficiency is made up, at least partially, by their thinness – higher efficiencies can be reached by stacking several thin-film cells on top of each other, each one tuned to work well at a specific frequency of light. This approach is not applicable to c-Si cells, which are thick as a result of their construction technique and are therefore largely opaque, blocking light from reaching other layers in a stack.  HP Pavilion dv7-3067nr CPU Fan

The main advantage of a-Si in large scale production is not efficiency, but cost. a-Si cells use approximately 1% of the silicon needed for typical c-Si cells, and the cost of the silicon is by far the largest factor in cell cost (no source). However, the higher costs of manufacture due to the multi-layer construction have, to date, made a-Si unattractive except in roles where their thinness or flexibility are an advantage. SONY Vaio VGN-CR23/N CPU Fan
Typically, amorphous silicon thin-film cells use a p-i-n structure. Typical panel structure includes front side glass, TCO, thin film silicon, back contact,polyvinyl butyral (PVB) and back side glass. UNI-SOLAR, a division of Energy Conversion Devices produces a version of flexible backings, used in roll-on roofing products.

Photovoltaic thermal hybrid solar collectors(PVT), are systems that convert solar radiation into thermal and electrical energy.HP Pavilion dv7-1129wm CPU Fan

These systems combine aphotovoltaic cell, which converts electromagnetic radiation (photons) into electricity, with a solar thermal collector, which captures the remaining energy and removes waste heat from the PV module. Photovoltaic (PV) cells suffer from a drop in efficiency with the rise in temperature due to increased resistance. HP Pavilion G72-b15EV CPU Fan

Most such systems can be engineered to carry heat away from the PV cells thereby cooling the cells and thus improving their efficiency by lowering resistance.[6]Although this is an effective method, it causes the thermal component to under-perform compared to a solar thermal collector. Recent research showed that a-Si:H PV with low temperature coefficients allow the PVT to be operated at high temperatures, creating a more symbiotic PVT system and improving performance of the a-Si:H PV by about 10%.Compaq Presario CQ60-417DX CPU Fan

Microcrystalline silicon (also called nanocrystalline silicon) is amorphous silicon, but also contains small crystals. It absorbs a broader spectrum of light and is flexible.

Micromorphous silicon module technology combines two different types of silicon, amorphous and microcrystalline silicon, in a top and a bottom photovoltaic cell. HP Pavilion dv7-3080eg CPU Fan

Sharp produces cells using this system in order to more efficiently capture blue light, increasing the efficiency of the cells during the time where there is no direct sunlight falling on them. Protocrystalline silicon is often used to optimize the open circuit voltage of a-Si photovoltaics.

Xunlight Corporation, which has received over $40 million of institutional investments,[ HP Pavilion dv9233ca CPU Fan

has completed the installation of its first 25 MW wide-web, roll-to-roll photovoltaic manufacturing equipment for the production of thin-film silicon PV modules.[9] Anwell Technologies has also completed the installation of its first 40 MW a-Si thin film solar panel manufacturing facility in Henan with its in-house designed multi-substrate-multi-chamber PECVD equipment. HP Envy 14-1195la CPU Fan

Polycrystalline silicon, also called polysilicon, is a material consisting of small silicon crystals. It differs from single-crystal silicon, used for electronics and solar cells, and from amorphous silicon, used for thin film devices and solar cells.

In single crystal silicon, the crystalline framework is homogenous, which can be recognized by an even external colouring.[1HP Pavilion dv6-2115sf CPU Fan

]In single crystal silicon, also called monocrystal, the crystal lattice of the entire sample is continuous and unbroken with no grain boundaries. Large single crystals are exceedingly rare in nature and can also be difficult to produce in the laboratory (see also recrystallisation). In contrast, in an amorphous structure the order in atomic positions is limited to short range. HP Pavilion dv7-3067nr CPU Fan

Polycrystalline and paracrystalline phases (see Polycrystal) are composed of a number of smaller crystals or crystallites.Polycrystalline silicon (or semicrystalline silicon, polysilicon, poly-Si, or simply "poly") is a material consisting of multiple small silicon crystals. Polycrystalline cells can be recognized by a visible grain, a “metal flake effect”. HP Pavilion dv7-1129wm CPU Fan

Semiconductor grade (also solar grade) polycrystalline silicon is converted to "single crystal" silicon – meaning that the randomly associated crystallites of silicon in "polycrystalline silicon" are converted to a large "single" crystal. Single crystal silicon is used to manufacture most Si-based microelectronic devices. Polycrystalline silicon can be as much as 99.9999% pure.[2] HP Pavilion G72-b15EV CPU Fan

Ultra-pure poly is used in the semiconductor industry, starting from poly rods that are two to three meters in length. In microelectronic industry (semiconductor industry), poly is used both at the macro-scale and micro-scale (component) level. Single crystals are grown using the Czochralski process, float-zone and Bridgman techniques. HP Pavilion dv6-2140se CPU Fan

At the component level, polysilicon has long been used as the conducting gate material in MOSFET and CMOS processing technologies. For these technologies it is deposited using low-pressure chemical-vapour deposition (LPCVD) reactors at high temperatures and is usually heavily doped n-type or p-type. SONY Vaio VGN-SZ6RXN/C CPU Fan

More recently, intrinsic and doped polysilicon is being used in large-area electronics as the active and/or doped layers inthin-film transistors. Although it can be deposited by LPCVD, plasma-enhanced chemical vapour deposition (PECVD), or solid-phase crystallization (SPC) of amorphous silicon in certain processing regimes, these processes still require relatively high temperatures of at least 300 °C. HP Pavilion dv7-2130ev CPU Fan

These temperatures make deposition of polysilicon possible for glass substrates but not forplastic substrates. The deposition of polycrystalline silicon on plastic substrates is motivated by the desire to be able to manufacture digital displays on flexible screens. Therefore, a relatively new technique called laser crystallization has been devised to crystallize a precursor amorphous silicon (a-Si) material on a plastic substrate without melting or damaging the plastic. ACER eMachines G520 CPU Fan

Short, high-intensity ultraviolet laser pulses are used to heat the deposited a-Si material to above the melting point of silicon, without melting the entire substrate. The molten silicon will then crystallize as it cools. By precisely controlling the temperature gradients, researchers have been able to grow very large grains, of up to hundreds of micrometers in size in the extreme case, although grain sizes of 10 nanometers to 1 micrometer are also common. HP Pavilion dv5-2132dx CPU Fan

In order to create devices on polysilicon over large-areas however, a crystal grain size smaller than the device feature size is needed for homogeneity of the devices. Another method to produce poly-Si at low temperatures is metal-induced crystallization where an amorphous-Si thin film can be crystallized at temperatures as low as 150C if annealed while in contact of another metal film such as aluminium, gold, or silver. Compaq Presario CQ60-307ea CPU Fan

Polysilicon has many applications in VLSI manufacturing. One of its primary uses is as gate electrode material for MOS devices. A polysilicon gate's electrical conductivity may be increased by depositing a metal (such as tungsten) or a metal silicide (such as tungsten silicide) over the gate. Polysilicon may also be employed as a resistor, a conductor, or as an ohmic contact for shallow junctions, with the desired electrical conductivity attained by doping the polysilicon material. HP Pavilion dv6-2010sa CPU Fan

One major difference between polysilicon and a-Si is that the mobility of the charge carriers of the polysilicon can be orders of magnitude larger and the material also shows greater stability under electric field and light-induced stress. This allows more complex, high-speed circuity to be created on the glass substrate along with the a-Si devices, which are still needed for their low-leakage characteristics. Toshiba Satellite A40-702 CPU Fan

When polysilicon and a-Si devices are used in the same process this is called hybrid processing. A complete polysilicon active layer process is also used in some cases where a small pixel size is required, such as in projection displays.

Polycrystalline silicon is also a key component of solar panel construction. Growth of the photovoltaic solar industry was limited by the supply of the polysilicon material.[3] SONY Vaio VGN-AR21B CPU Fan

For the first time, in 2006, over half of the world's supply of polysilicon was being used for production of renewable electricity solar power panels.[4] Only twelve factories were known to produce solar-grade polysilicon in 2008, however by 2013 the number now stands at over 100 manufacturers.[5] Monocrystalline silicon is higher priced and more efficient than polycrystalline. SONY Vaio VPC-EB3E1E/PI CPU Fan

Polysilicon deposition, or the process of depositing a layer of polycrystalline silicon on a semiconductor wafer, is achieved by pyrolyzing silane (SiH4) at 580 to 650 °C. This pyrolysis process releases hydrogen.

Polysilicon layers can be deposited using 100% silane at a pressure of 25–130 Pa (0.2 to 1.0 Torr) or with 20–30% silane (diluted in nitrogen) at the same total pressure. SONY Vaio VPC-EB3E1E/WI CPU Fan

Both of these processes can deposit polysilicon on 10–200 wafers per run, at a rate of 10–20 nm/min and with thickness uniformities of ±5%. Critical process variables for polysilicon deposition include temperature, pressure, silane concentration, and dopant concentration. Wafer spacing and load size have been shown to have only minor effects on the deposition process.SONY Vaio VGN-FS660/W CPU Fan

The rate of polysilicon deposition increases rapidly with temperature, since it followsArrhenius behavior, that is deposition rate = A·exp(–qEa/kT) where q is electron charge and k is the Boltzmann constant. The activation energy (Ea) for polysilicon deposition is about 1.7 eV. Based on this equation, the rate of polysilicon deposition increases as the deposition temperature increases. HP Pavilion G61-631NR CPU Fan

There will be a minimum temperature, however, wherein the rate of deposition becomes faster than the rate at which unreacted silane arrives at the surface. Beyond this temperature, the deposition rate can no longer increase with temperature, since it is now being hampered by lack of silane from which the polysilicon will be generated. Such a reaction is then said to be 'mass-transport-limited.'HP Pavilion dv6560el CPU Fan

When a polysilicon deposition process becomes mass-transport-limited, the reaction rate becomes dependent primarily on reactant concentration, reactor geometry, and gas flow.

When the rate at which polysilicon deposition occurs is slower than the rate at which unreacted silane arrives, then it is said to be surface-reaction-limited. HP Pavilion dv6-2128ca CPU Fan

A deposition process that is surface-reaction-limited is primarily dependent on reactant concentration and reaction temperature. Deposition processes must be surface-reaction-limited because they result in excellent thickness uniformity and step coverage. A plot of the logarithm of the deposition rate against the reciprocal of the absolute temperature in the surface-reaction-limited region results in a straight line whose slope is equal to –qEa/k. HP Pavilion dv7-3004el CPU Fan

At reduced pressure levels for VLSI manufacturing, polysilicon deposition rate below 575 °C is too slow to be practical. Above 650 °C, poor deposition uniformity and excessive roughness will be encountered due to unwanted gas-phase reactions and silane depletion. Pressure can be varied inside a low-pressure reactor either by changing the pumping speed or changing the inlet gas flow into the reactor. HP Pavilion dv7-4050ev CPU Fan

If the inlet gas is composed of both silane and nitrogen, the inlet gas flow, and hence the reactor pressure, may be varied either by changing the nitrogen flow at constant silane flow, or changing both the nitrogen and silane flow to change the total gas flow while keeping the gas ratio constant. Recent investigations have shown that e-beam evaporation, HP G42-367TU CPU Fan

followed by SPC (if needed) can be a cost effective and faster alternative for producing solar grade poly-Si thin films.[6] Modules produced by such method are shown to have an photovoltaic efficiency of ~6%.[7]

Polysilicon doping, if needed, is also done during the deposition process, usually by adding phosphine, arsine, or diborane. HP Pavilion dv5-1172el CPU Fan

Adding phosphine or arsine results in slower deposition, while adding diborane increases the deposition rate. The deposition thickness uniformity usually degrades when dopants are added during deposition.

Upgraded metallurgical-grade (UMG) silicon (also known as UMG-Si) solar cell is being produced as a low cost alternative to polysilicon created by the Siemens process. UMG greatly reduces impurities in a variety of ways that require less equipment and energy than the Siemens process.[8] Toshiba Satellite A105-S4084 CPU Fan

UMG is about 99% pure which is three or more orders of magnitude less pure and about 10 times less expensive than polysilicon ($1.70 to $3.20 per kg from 2005 to 2008 compared to $40 to $400 per kg for polysilicon). It has the potential to provide nearly-as-good solar cell efficiency at 1/5 the capital expenditure, half the energy requirements, and less than $15/kg.[9] HP Pavilion dv4-1038tx CPU Fan

In 2008 several companies were touting the potential of UMG in 2010, but the credit crisis greatly lowered the cost of polysilicon and several UMG producers put plans on hold.[10][11] The Siemens process will remain the dominant form of production for years to come due to more efficiently implementing the Siemens process. GT Solar claims a new Siemens process can produce at $27/kg and may reach $20/kg in 5 years. HP Pavilion dv7-3060sb CPU Fan

GCL-Poly expects production costs to be $20/kg by end of 2011.[12] Elkem Solar estimates their UMG costs to be $25/kg, with a capacity of 6,000 tonnes by the end of 2010. Calisolar expects UMG technology to produce at $12/kg in 5 years with boron at 0.3 ppm and phosphorus at 0.6 ppm.[13] At $50/kg and 7.5 g/W, module manufacturers spend $0.37/W for the polysilicon. HP Pavilion dv7-6055sf CPU Fan

For comparison, if a CdTe manufacturer pays spot price for tellurium ($420/kg in April 2010) and has a 3 micron thickness, their cost would be 10 times less, $0.037/Watt. At 0.1 g/W and $31/ozt for silver, polysilicon solar producers spend $0.10/W on silver.[14]

Q-Cells, Canadian Solar, and Calisolar have used Timminco UMG. SONY VGN-CS108D  CPU Fan

Timminco is able to produce UMG-Si with 0.5 ppm boron for $21/kg but were sued by shareholders because they had expected $10/kg.[15] RSI and Dow Corning have also been in litigation over UMG-Si technology.

The polysilicon manufacturing market is growing very fast. According to Digitimes, in July 2011, the total polysilicon production in 2010 was 209,000 tons. DELL XPS M170 CPU Fan

First-tier suppliers account for 64% of the market while China-based polysilicon firms have 30% of market share. The total production is likely to increase 37.4% to 281,000 tons by end of 2011.[17] For 2012,EETimes Asia predicts 328,000 tons production with only 196,000 tons of demand, with spot prices expected to fall 56%. While good for renewable energy prospects, the subsequent drop in price could be brutal for manufacturers.[18] HP Pavilion G72-b15SV CPU Fan

As of late 2012, SolarIndustryMag reports a capacity of 385,000 tons will be reached by yearend 2012.[19]

But as established producers (mentioned below) expand their capacities, additional newcomers – many from Asia – are moving into the market. Even long-time players in the field have recently had difficulties expanding plant production. HP G62-120ES CPU Fan

It is yet unclear which companies will be able to produce at costs low enough to be profitable after the steep drop in spot-prices of the last months.

Prices of polysilicon are often divided into two categories, contract and spot prices, and higher purity commands higher prices. While in booming installation times, price rally occurs in polysilicon. HP Pavilion dv6-3034ss   CPU   Fan

Not only spot prices surpass contract prices in the market; but it is also hard to acquire enough polysilicon. Buyers will accept down payment and long term agreements to acquire a large enough volume of polysilicon. On the contrary, spot prices will be below contract prices once the solar PV installation is in a down trend. In late 2010, booming installation brought up the spot prices of polysilicon. HP Pavilion dv7-3165ef  CPU Fan

In the first half of 2011, prices of polysilicon kept strong owing to the FIT policies of Italy. The solar PV price survey and market research firm, PVinsights,[42] reported that the prices of polysilicon might be dragged down by lack of installation in the second half of 2011.[43] As recently as 2008 prices were over $400/kg spiking from levels around $200/kg, while seen falling to $15/kg in 2013. HP X16-1000 Series CPU Fan

Black silicon is a semiconductor material, a surface modification of silicon with very low reflectivity and correspondingly high absorption of visible (andinfrared) light. The modification was discovered in the 1980s as an unwanted side effect of reactive ion etching (RIE).[1][2] Another method for forming a similar structure was developed in Eric Mazur's laboratory at Harvard University (1998). IBM ThinkPad Z61m  CPU Fan

Black silicon is a needle-shaped surface structure where needles are made of single-crystal silicon and have a height above 10 µm and diameter less than 1 µm.[2] Its main feature is an increased absorption of incident light—the high reflectivity of the silicon, which is usually 20–30% for quasi-normal incidence, is reduced to about 5%. This is due to the formation of a so-called effective medium[3] by the needles. ACER Aspire One D250 CPU Fan

Within this medium, there is no sharp interface, but a continuous change of therefractive index that reduces Fresnel reflection. When the depth of the graded layer is roughly equal to the wavelength of light in silicon (about one-quarter the wavelength in vacuum) the reflection is reduced to 5%; deeper grades produce even blacker silicon. [4] For low reflectivity, ACER Ferrari 4000 CPU Fan

the nanoscale features producing the index graded layer must be smaller than the wavelength of the incident light to avoid scattering.

In semiconductor technology, reactive-ion etching (RIE) is a standard procedure for producing trenches and holes with a depth of up to several hundred micrometres and very high aspect ratios. HP G42-367TU CPU Fan

In Bosch process RIE, this is achieved by repeatedly switching between an etching and passivation. With cryogenic RIE, the low temperature and oxygen gas achieve this sidewall passivation by forming SiO2, easily removed from the bottom by directional ions. Both RIE methods can produce black silicon, but the morphology of the resulting structure differs substantially. Toshiba Satellite L350-146 CPU Fan

The switching between etching and passivation of the Bosch process creates undulated sidewalls, which are visible also on the black silicon formed this way.During etching, however, small debris remain on the substrate; they mask the ion beam and produce structures that are not removed and in the following etching steps and result in tall silicon pillars.[15] The process can be set so that a million needles are formed on an area of one square millimeter. HP Pavilion dv8335ea CPU Fan

In 1999, a group led by Eric Mazur and James Carey at the Harvard University developed a process in which black silicon was produced by irradiating silicon with femtosecond laser pulses.[16] After irradiation in the presence of a gas containingsulfur hexafluoride and other dopants, the surface of silicon develops a self-organized microscopic structure of micrometer-sized cones. Dell Vostro 3400 CPU Fan

The resulting material has many remarkable properties, such as an enhanced absorption that extends to theinfrared below the band gap of silicon, including the wavelengths for which unmodified silicon is transparent. This property is caused by sulfur atoms being forced to the silicon surface, creating a structure with a lower band gap and therefore the ability to absorb longer wavelengths. APPLE MG62090V1-Q020-S99 CPU Fan

Similar surface modification can be achieved in vacuum using the same type of laser and laser processing conditions. In this case, the individual silicon micro-cones lack sharp tips (see image). The reflectivity of such a micro-structured surface is very low, 3-14% in the spectral range 350–1150 nm.[17] Such reduction in reflectivity is considered to be contributed by the geometry of these micro-cones, which increases the light internal reflections between them. APPLE 15" Macbook Pro Unibody CPU Fan

Hence, the possibility of light absorption by the silicon is increased. The gain in absorption achieved by fs laser texturization is found to be superior to that achieved by using an alkaline chemical etch method,[18] which is a standard industrial approach for surface texturing of mono-crystalline silicon wafers in solar cell manufacturing. It is also found that such surface modification is independent of local crystalline orientation. Gateway 6020GZ CPU Fan

A uniform texturing effect can be achieved across the whole surface of a multi-crystalline silicon wafer. The very steep angles lower the reflection to near zero and also increase the probability of recombination, which is why it thus far has not been used in solar cell manufacturing.

The material has not yet found commercial applications[   but potentially could find in a number of photodetectors for various imaging and night vision applications. Toshiba Satellite Pro M30-891 CPU Fan

Black silicon is currently being commercialized by SiOnyx, a Massachusetts-based venture-funded startup company which acquired licensing for the process from Harvard in 2006.

Black silicon also has potential application for high-efficiency solar cells, which is being explored by Solasys, an EU Seventh Framework Programme (FP7) funded demonstration project aiming at lowering manufacturing costs while increasing cell efficiency at the same time. Toshiba Satellite Pro M30-782 CPU Fan

A group at the National Renewable Energy Laboratory has reported black silicon solar cells with 18.2% confirmed efficiency.[21] This black silicon anti-reflective surface was formed by a metal-assisted etch process using nano particles of silver.

Printed electronics is a set of printing methods used to create electrical devices on various substrates. HP Pavilion dv5-1050eo CPU Fan

Printing typically uses common printing equipment or other low-cost equipment suitable for defining patterns on material, such asscreen printing, flexography, gravure, offset lithography, and inkjet. Electrically functional electronic or optical inks are deposited on the substrate, creating active or passive devices, such as thin film transistors or resistors. SONY VGN-SZ220 CPU Fan

Printed electronics is expected to facilitate widespread, very low-cost, low-performance electronics for applications such asflexible displays, smart labels, decorative and animated posters, and active clothing that do not require high performance.[1]

The term printed electronics is related to organic electronics or plastic electronics, in which one or more inks are composed of carbon-based compounds. Dell Studio XPS 1645 CPU Fan

These other terms refer to the ink material, which can be deposited by solution-based, vacuum-based or some other method. Printed electronics, in contrast, specifies the process, and can utilize any solution-based material, including organic semiconductors, inorganic semiconductors, metallic conductors, nanoparticles, nanotubes, etc. ACER eMachines 7230 CPU Fan

For the preparation of printed electronics nearly all industrial printing methods are employed. Similar to conventional printing, printed electronics applies ink layers one atop another.[2] so that the coherent development of printing methods and ink materials are the field's essential tasks.

The most important benefit of printing is low-cost volume fabrication. DELL Latitude E4300 CPU Fan

The lower cost enables use in more applications.[3] An example is RFID-systems, which enable contactless identification in trade and transport. In some domains, such as light-emitting diodes printing does not impact performance.[2] Printing on flexible substrates allows electronics to be placed on curved surfaces, for example, putting solar cells on vehicle roofs. SONY Vaio VGN-A29LP CPU Fan

sMore typically, conventional semiconductors justify their much higher costs by providing much higher performance.

The maximum required resolution of structures in conventional printing is determined by the human eye. Feature sizes smaller than approximately 20 µm cannot be distinguished by the human eye and consequently exceed the capabilities of conventional printing processes.[4] HP Pavilion dv7t-6100 CTO CPU Fan

In contrast, higher resolution and smaller structures are necessary in electronics printing, because they directly affect circuit density and functionality (especially transistors). A similar requirement holds for the precision with which layers are printed on top of each other (layer to layer registration).

Control of thickness, holes, and material compatibility (wetting, adhesion, solvation) are essential, but matter in conventional printing only if the eye can detect them. Conversely, the visual impression is irrelevant. HP Pavilion dv7-3163cl CPU Fan

The attraction of printing technology for the fabrication of electronics mainly results from the possibility of preparing stacks of micro-structured layers (and thereby thin-film devices) in a much simpler and cost-effective way compared to conventional electronics.[6] Also, the ability to implement new or improved functionalities (e.g. mechanical flexibility) plays a role. HP Pavilion dv7-4140ed CPU Fan

The selection of the printing method used is determined by requirements concerning printed layers, by the properties of printed materials as well as economic and technical considerations of the final printed products.

Printing technologies divide between sheet-based and roll-to-roll-based approaches. Sheet-based techniques, such as inkjet and screen printing are best for low-volume, high-precision work. Compaq Presario CQ60-155ep CPU Fan

Gravure, offset and flexographic printing are more common for high-volume production, such as solar cells, reaching 10.000 square meters per hour (m²/h).[4][6] While offset and flexographic printing are mainly used for inorganic[7][8] and organic[9][10] conductors (the latter also for dielectrics),[11] gravure printing is especially suitable for quality-sensitive layers like organic semiconductors and semiconductor/dielectric-interfaces in transistors, HP Mini 110-3000sd CPU Fan

due to high layer quality.[11] In connection with high resolution, is also suitable for inorganic[12] and organic[13] conductors. Organic field-effect transistors and integrated circuits can be prepared completely by means of mass-printing methods.[11]

Inkjets are flexible and versatile, and can be set up with relatively low effort. Inkjets are probably the most commonly used method.[1Compaq Presario CQ60-155ep CPU Fan

4] However, inkjets offer lower througput of around 100 m2/h and lower resolution (ca. 50 µm).[4] It is well suited for low-viscosity, soluble materials like organic semiconductors. With high-viscosity materials, like organic dielectrics, and dispersed particles, like inorganic metal inks, difficulties due to nozzle clogging occur. Because ink is deposited via droplets, SONY Vaio VPC-EA46FM/B CPU Fan

thickness and dispersion homogeneity is reduced. Simultaneously using many nozzles and pre-structuring the substrate allows improvements in productivity and resolution, respectively. However, in the latter case non-printing methods must be employed for the actual patterning step.[15]Inkjet printing is preferable for organic semiconductors in organic field-effect transistors (OFETs) and organic light-emitting diodes (OLEDs) Toshiba Satellite L500-1XL CPU Fan

, but also OFETs completely prepared by this method have been demonstrated.[16] Frontplanes[17] and backplanes[18] of OLED-displays, integrated circuits,[19] organic photovoltaic cells (OPVCs)[20] and other devices can be prepared with inkjets.

Screen printing is appropriate for fabricating electrics and electronics on industrial scales due to its ability to produce thick layers from paste-like materials. HP Mini 110-3000sd CPU Fan

This method can produce conducting lines from inorganic materials (e.g. for circuit boards and antennas), but also insulating and passivating layers, whereby layer thickness is more important than high resolution. Its 50 m²/h throughput and 100 µm resolution are similar to inkjets.[4] This versatile and comparatively simple method is used mainly for conductive and dielectric layers,[21][22] HP Pavilion dv7-3162nr CPU Fan

but also organic semiconductors, e.g. for OPVCs,[23] and even complete OFETs[17] can be printed.

Aerosol Jet Printing (also known as Maskless Mesoscale Materials Deposition or M3D)[24] is another material deposition technology for printed electronics. The Aerosol Jet process begins with atomization of an ink, which can be heated up to 80 °C, producing droplets on the order of one to two micrometres in diameter. HP 480481-001 CPU Fan

The atomized droplets are entrained in a gas stream and delivered to the print head. Here, an annular flow of clean gas is introduced around the aerosol stream to focus the droplets into a tightly collimated beam of material. The combined gas streams exit the print head through a converging nozzle that compresses the aerosol stream to a diameter as small as 10 µm. HP 622029-001 CPU Fan

The jet of droplets exits the print head at high velocity (~50 meters/second) and impinges upon the substrate. Electrical interconnects, passive and active components[25] are formed by moving the print head, equipped with a mechanical stop/start shutter, relative to the substrate. The resulting patterns can have features ranging from 10 µm wide, with layer thicknesses from tens of nanometers to >10 µm.[26] Toshiba Satellite L555-12P CPU Fan

A wide nozzle print head enables efficient patterning of millimeter size electronic features and surface coating applications. All printing occurs without the use of vacuum or pressure chambers and at room temperature. The high exit velocity of the jet enables a relatively large separation between the print head and the substrate, typically 2–5 mm. HP GB0507PGV1-A CPU Fan

The droplets remain tightly focused over this distance, resulting in the ability to print conformal patterns over three dimensional substrates. Despite the high velocity, the printing process is gentle; substrate damage does not occur and there is generally no splatter or overspray from the droplets.[27] Once patterning is complete, the printed ink typically requires post treatment to attain final electrical and mechanical properties. HP Pavilion dv7-1135nr CPU Fan

Post-treatment is driven more by the specific ink and substrate combination than by the printing process. A wide range of materials has been successfully deposited with the Aerosol Jet process, including diluted thick film pastes, thermosetting polymers such as UV-curable epoxies, and solvent-based polymers like polyurethane and polyimide, and biologic materials.[28]Dell Latitude E6510 CPU Fan

Other methods with similarities to printing, among them microcontact printing and nano-imprint lithography are of interest.[29] Here, µm- and nm-sized layers, respectively, are prepared by methods similar to stamping with soft and hard forms, respectively. Often the actual structures are prepared subtractively, e.g. by deposition of etch masks or by lift-off processes. For example electrodes for OFETs can be prepared.[30][31] DELL DC280005FF0 CPU Fan

Sporadically pad printing is used in a similar manner.[32] Occasionally so-called transfer methods, where solid layers are transferred from a carrier to the substrate, are considered printed electronics.[33]Electrophotography is currently not used in printed electronics.

Both organic and inorganic materials are used for printed electronics. HP KSB0605HB CPU Fan

Ink materials must be available in liquid form, for solution, dispersion or suspension.[34] They must function as conductors, semiconductors, dielectrics, or insulators. Material costs must be fit for the application.

Electronic functionality and printability can interfere with each other, mandating careful optimization.[5] For example, a higher molecular weight in polymers enhances conductivity, but diminishes solubility. HP 580696-001 CPU Fan

For printing, viscosity, surface tension and solid content must be tightly controlled. Cross-layer interactions such as wetting, adhesion, and solubility as well as post-deposition drying procedures affect the outcome. Additives often used in conventional printing inks are unavailable, because they often defeat electronic functionality.

Material properties largely determine the differences between printed and conventional electronics. HP Pavilion dv7-4014eo CPU Fan

Printable materials provide decisive advantages beside printability, such as mechanical flexibility and functional adjustment by chemical modification (e.g. light color in OLEDs).[35]

Printed conductors offer lower conductivity and charge carrier mobility.[36]

With a few exceptions, inorganic ink materials are dispersions of metallic or semiconducting micro- and nano-particles. DELL Studio 1555 CPU Fan

Semiconducting nanoparticles used include silicon [37] and oxide semiconductors.[38] Silicon is also printed as an organic precursor [39] which is then converted by pyrolisis and annealing into crystalline silicon.

Organic printed electronics integrates knowledge and developments from printing, electronics, chemistry, and materials science, especially from organic and polymer chemistry. HP G62-339WM CPU Fan

Organic materials in part differ from conventional electronics in terms of structure, operation and functionality,[41] which influences device and circuit design and optimization as well as fabrication method.[42]

The discovery of conjugated polymers[36] and their development into soluble materials provided the first organic ink materials.HP Pavilion dv5-1145ev CPU Fan

Materials from this class of polymers variously possess conducting, semiconducting, electroluminescent, photovoltaic and other properties. Other polymers are used mostly as insulators and dielectrics.

In most organic materials, hole transport is favored over electron transport.[43] HP F787 CPU Fan

Recent studies indicate that this is a specific feature of organic semiconductor/dielectric-interfaces, which play a major role in OFETs.[44] Therefore p-type devices should dominate over n-type devices. Durability (resistance to dispersion) and lifetime is less than conventional materials.[40]

Organic semiconductors include the conductive polymers poly(3,4-ethylene dioxitiophene), dHP Pavilion dv7-3155eb CPU Fan

oped with poly(styrene sulfonate), (PEDOT:PSS) and poly(aniline) (PANI). Both polymers are commercially available in different formulations and have been printed using inkjet,[45] screen[21] and offset printing[9] or screen,[21] flexo[10] and gravure[13] printing, respectively.

Polymer semiconductors are processed using inkjet printing, such as poly(thiopene)s like poly(3-hexylthiophene) (P3HT)[46] and poly(9,9-dioctylfluorene co-bithiophen) (F8T2).[47DELL Studio 1458 CPU Fan

] The latter material has also been gravure printed.[11] Different electroluminescent polymers are used with inkjet printing,[15] as well as active materials for photovoltaics (e.g. blends of P3HT with fullerene derivatives),[48] which in part also can be deposited using screen printing (e.g. blends of poly(phenylene vinylene) with fullerene derivatives).[23] Toshiba Satellite A505-S6970 CPU Fan

Printable organic and inorganic insulators and dielectrics exist, which can be processed with different printing methods.Inorganic electronics provides highly ordered layers and interfaces that organic and polymer materials cannot provide.Silver nanoparticles are used with flexo,[8] offset [50] and inkjet.[51] Gold particles are used with inkjet.[52] HP Pavilion dv6-3090si CPU Fan

A.C. electroluminescent (EL) multi-color displays can cover many tens of square meters, or be incorporated in watch faces and instrument displays. They involve six to eight printed inorganic layers, including a copper doped phosphor, on a plastic film substrate.[53]

Silicon inks are used commercially in transistor circuits for RFID labels,[54] selective emitters and dopant layers for photovoltaics,[55] and temperature sensors.[5HP G60-215EM CPU Fan

6] Fully printed field effect transistors produced at room temperature using silicon nanoparticles have been demonstrated,[57] but the field effect mobility is low compared to crystalline silicon (being similar to that obtained in amorphous silicon transistors). In printed nanoparticle silicon, the low mobility arises from an activated charge transport between nanoparticles,Toshiba Satellite A100-011 CPU Fan

which in turn enables its use as a negative temperature coefficient (NTC) thermistor material.[58] The corresponding varistor characteristics have recently been used to develop a current switching transistor,[59] which works as a two-way switch by changing the conductivity between the different pairs of terminals.

CIGS cells can be printed directly onto molybdenum coated glass sheets. DELL XPS M1210 CPU Fan

 HP G62-120SL CPU Fan

A printed gallium arsenide germanium solar cell demonstrated 40.7% conversion efficiency, eight times that of the best organic cells, approaching the best performance of crystalline silicon.

Printed electronics allows the use of flexible substrates, which lowers production costs and allows fabrication of mechanically flexible circuits. HP Pavilion dv6-2117eo CPU Fan

While inkjet and screen printing typically imprint rigid substrates like glass and silicon, mass-printing methods nearly exclusively use flexible foil and paper.Poly(ethylene terephthalate)-foil (PET) is a common choice, due to its low cost and higher temperature stability. Poly(ethylene naphthalate)- (PEN) andpoly(imide)-foil (PI) are alternatives. Toshiba Satellite L305D-S5950 CPU Fan

Paper's low costs and manifold applications make it an attractive substrate, however, its high roughness and large absorbency make it problematic for electronics.[50]

Other important substrate criteria are low roughness and suitable wettability, which can be tuned pre-treatment (coating, corona). In contrast to conventional printing, high absorbency is usually disadvantageous. SONY Vaio VGN-BZ11MN CPU Fan

Monocrystalline silicon or single-crystal Si, or mono-Si is the base material of the electronic industry. It consists of silicon in which the crystal lattice of the entire solid is continuous, unbroken (with no grain boundaries) to its edges. It can be preparedintrinsic, i.e. made of exceedingly pure silicon alone, or doped, containing very small quantities of other elements added to change in a controlled manner its semiconducting properties. SONY Vaio VGN-TX91S CPU Fan

Most silicon monocrystals are grown by the Czochralski process, in the shape of cylinders up to 2 m long and 45 cm in diameter (figure on the right), which, cut in thin slices, give the wafers onto which the microcircuits will be fabricated.

Single-crystal silicon is perhaps the most important technological material of the last decades (the "silicon era"),[1] Toshiba Satellite A100-849 CPU Fan

because its availability at an affordable cost has been essential for the development of the electronic devices on which the present day electronic and informatic revolution is based.

VLSI devices (Intel) fabricated on a single-crystal silicon wafer)

Monocrystalline is opposed to amorphous silicon, in which the atomic order is limited to short range order only. Gateway MT6400 CPU Fan

In between the two extremes there is polycrystalline silicon, which is made up of small crystals, known as crystallites.

The monocrystalline form is used in the semiconductor device fabrication since grain boundaries would bring discontinuities and favor imperfections in the microstructure of silicon, such as impurities and crystallographic defects, which can have significant effects on the local electronic properties of the material. Toshiba Satellite A100-849 CPU Fan

On the scale that devices operate on, these imperfections would have a significant impact on the functionality and reliability of the devices. Without the crystalline perfection, it would be virtually impossible to build Very Large-Scale Integration (VLSI) devices (figure at right), in which millions (up to billions, circa 2005[2]) of transistor-based circuits, all of which must reliably be working, are combined into a single chip to get e.g. a microprocessor. Dell Vostro 3350 CPU Fan

Therefore, electronic industry has invested heavily in facilities to produce large single crystals of silicon.

Monocrystalline silicon is also used in the manufacturing of high performance solar cells. Since, however, solar cells are less demanding than microelectronics for as concerns structural imperfections, monocrystaline solar grade (Sog-Si) is often used, single crystal is also often replaced by the cheaper polycrystalline or multicrystalline silicon.[3ACER Aspire 4733 CPU Fan

] Monocrystalline solar cells can achieve 21% efficiency[4] whereas other types of less expensive cells including thin film and polycrystallineare only capable of achieving around 10% efficiency.[5]

Few solar charger companies use monocrystalline solar panels because of the higher cost to produce the solar cells, although these higher efficiency products are starting to pop up as consumers demand more efficient products. ACER Aspire 3003LCi CPU Fan

The 2010 Consumer Electronics Show showcased one of these high-efficiency monocrystalline chargers known as the JOOS Orange and awarded it the 2010 Best of Innovations Award. HP Pavilion dv7-6187cl CPU Fan,HP Pavilion dv7-1128ca CPU Fan,HP Pavilion dv6-3216us CPU Fan

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