thin film solar cell

Cross-section of thin filmpolycrystalline solar cell.

Possible combinationsof Group-(I, III, VI)elements in theperiodic table thatyielda compound showingphotovoltaic effect(Cu, Ag, Au | Al, Ga, In| S, Se, Te).

Thin film solar cellFrom Wikipedia, the free encyclopedia

A thin-film solar cell (TFSC), also called a thin-film photovoltaic cell(TFPV), is a solar cell that is made by depositing one or more thin layers(thin film) of photovoltaic material on a substrate. The thickness range ofsuch a layer is wide and varies from a few nanometers to tens ofmicrometers.

Many different photovoltaic materials are deposited with variousdeposition methods on a variety of substrates. Thin-film solar cells areusually categorized according to the photovoltaic material used:

Amorphous silicon (a-Si) and other thin-film silicon (TF-Si)Cadmium Telluride (CdTe)Copper indium gallium selenide (CIS or CIGS)Dye-sensitized solar cell (DSC) and other organic solar cells

Contents

1 History2 Thin-film silicon

2.1 Design and fabrication2.2 Micromorphous silicon2.3 Efficiency2.4 Building integrated photovoltaics

3 Organic solar cells4 Efficiencies, volumes and prices5 Production, cost and market6 Installations7 Time Award8 See also9 Notes10 Sources

History

Initially appearing as small strips powering hand-held calculators, thin-film PV is now available in very largemodules used in sophisticated building-integrated installations and vehicle charging systems. GBI Researchprojects thin film production to grow 24% from 2009 levels and to reach 22,214 MW in 2020. "Expectations arethat in the long-term, thin-film solar PV technology would surpass dominating conventional solar PVtechnology, thus enabling the long sought-after grid parity objective."[1][2]

Thin-film silicon

A silicon thin-film cell is a thin-film cell that uses amorphous (a-Si or a-Si:H), protocrystalline, nanocrystalline

Thin film solar cell - Wikipedia, the free encyclopedia http://en.wikipedia.org/wiki/Thin_film_solar_cell

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Solar Cell Efficiencies

(nc-Si or nc-Si:H) or black silicon. Thin-film silicon is opposed to wafer (or bulk) silicon (monocrystalline orpolycrystalline).

Design and fabrication

The silicon is mainly deposited by chemical vapor deposition, typically plasma-enhanced (PE-CVD), from silanegas and hydrogen gas. Other deposition techniques being investigated include sputtering and hot wiretechniques.

The silicon is deposited on glass, plastic or metal which has been coated with a layer of transparent conductingoxide (TCO).

A p-i-n structure is usually used, as opposed to an n-i-p structure. This is because the mobility of electrons ina-Si:H is roughly 1 or 2 orders of magnitude larger than that of holes, and thus the collection rate of electronsmoving from the p- to n-type contact is better than holes moving from p- to n-type contact. Therefore, thep-type layer should be placed at the top where the light intensity is stronger, so that the majority of the chargecarriers crossing the junction would be electrons.[3].

Micromorphous silicon

Micromorphous silicon module technology combines two different types of silicon, amorphous andmicrocrystalline, in a top and a bottom photovoltaic cell. Use of protocrystalline silicon for the intrinsic layer hasshown to optimize the open circuit voltage of an a-Si photovoltaic cell.[4]

Efficiency

These types of silicon present dangling and twisted bonds, which results indeep defects (energy levels in the bandgap) as well as deformation of thevalence and conduction bands (band tails). The solar cells made from thesematerials tend to have lower energy conversion efficiency than bulk silicon(also called crystalline or wafer silicon), but are also less expensive toproduce. The quantum efficiency of thin-film solar cells is also lower due toreduced number of collected charge carriers per incident photon.

Amorphous silicon has a higher bandgap (1.7 eV) than crystalline silicon(c-Si) (1.1 eV), which means it absorbs the visible part of the solar spectrummore strongly than the infrared portion of the spectrum. As nc-Si has about the same bandgap as c-Si, the nc-Siand a-Si can advantageously be combined in thin layers, creating a layered cell called a tandem cell. The top cellin a-Si absorbs the visible light and leaves the infrared part of the spectrum for the bottom cell in nc-Si.

Recently, solutions to overcome the limitations of thin-film silicon have been developed. Light trapping schemeswhere the incoming light is obliquely coupled into the silicon and the light traverses the film several timesenhance the absorption of sunlight in the films. Thermal processing techniques enhance the crystallinity of thesilicon and pacify electronic defects.[citation needed]

Building integrated photovoltaics


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Thin film photovoltaic panels beinginstalled onto a roof

Thin film solar panels are commercially available for installation onto theroofs of buildings, either applied onto the finished roof, or integrated intothe roof covering. The advantage over tradition PV panels is that theyare very low in weight, are not subject to wind lifting, and can be walkedon (with care). The comparable disadvantages are increased cost andreduced efficiency.

A silicon thin film technology is being developed for building integratedphotovoltaics (BIPV) in the form of semitransparent solar cells whichcan be applied as window glazing. These cells function as window tintingwhile generating electricity.

Organic solar cells

The Organic solar cell is another alternative to the more conventional materials used to make photovoltaics.Although a very novel technology it is promising since it offers a very low cost solution.

Efficiencies, volumes and prices

Since the invention of the first modern silicon solar cell in 1954, incremental improvements have resulted inmodules capable of converting 12 to 18 percent of solar radiation into electricity.[5] The performance andpotential of thin-film materials are high, reaching cell efficiencies of 12%-20%; prototype module efficiencies of7%-13%; and production modules in the range of 9%. Future module efficiencies are expected to climb close tothe state-of-the-art of today's best cells, or to about 10-16%.[6]

Annual manufacturing volume in the United States has grown from about 12 megawatts (MW) per year in 2003to more than 20 MW/yr in 2004; 40-50 MW/yr production levels are expected in 2005 with continued rapidgrowth in the years after that.

Costs are expected to drop to below $100/m2 in volume production, and could reach even lower levels—wellunder $50/m2, the DOE/NREL goal for thin films—when fully optimized. At these levels, thin-film modules willcost less than fifty cents per watt to manufacture, opening new markets such as cost-effective distributed powerand utility production to thin-film electricity generation.[7]

As crystalline silicon price rose, the production cost of silicon-based solar cell module in 2008 was at some point4-5 times higher than that of thin film modules. Thin-film producers still enjoy in 2009 price advantage as itsproduction cost is 20% less than that of silicon modules.It is expected that the production cost of thin-film willcontinue dropping (40% less than silicon), as Chinese producers are now putting more resources into R&D andpartnering with manufacturing equipment suppliers[8]

Production, cost and market


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In recent years, the manufacturers of thin-film solar modules are bringing costs down and gaining in competitivestrength through advanced thin film technology. However, the traditional crystalline silicon technologies will notgive up their market positions for a few years because they still hold considerable development potential interms of the cost. Efficiency of thin film solar is considerably lower and thin film solar manufacturing equipmentsuppliers intend to score costs of below USD 1/W, and Anwell Technologies Limited claimed that they intend tobring it down further to USD 0.5/W.[9] Those equipment suppliers have been doing R&D for micro-morphoussilicon modules since 2008. This technology represents a development based on the thin-film panels made ofordinary amorphous silicon marketed at present that brings higher cell efficiency by depositing an additionalabsorber layer made of micro crystalline silicon on the amorphous layer. Some equipment suppliers even claimthat there will be machinery in market to manufacture these new modules at $0.70.[10] With such potential offurther development of thin film solar technology, the European Photovoltaic Industry Association (EPIA)expects that manufacturing capacities for these technologies will double to over 4GW by 2010 representing amarket share of around 20%.[11]

Installations

First Solar, the CdTe thin-film manufacturer stated that "at the end of 2007, over 300 MW of First Solar PVmodules had been installed worldwide." Below is a list of several recent installations:[6]

Since 16 October 2008, Germany's largest thin-film pitched roof system, constructed by Riedel Recycling,has been in operation and producing solar power in Moers near Duisburg. Over eleven thousand cadmiumtelluride modules, from First Solar, deliver a total of 837 kW [12].First Solar recently completed a 2.4 MW rooftop installation as part of Southern California Edisonprogram to install 250 MW of rooftop solar panels throughout Southern California over by 2013.[13]

First Solar announced a 7.5 MW system to be installed in Blythe, CA, where the California Public UtilitiesCommission has accepted a 12 ¢/kWh power purchase agreement with First Solar (after the application ofall incentives).[14]

Construction of a 10 MW plant in the Nevada desert began in July 2008. [1] (http://investor.firstsolar.com/releasedetail.cfm?ReleaseID=324202) [2] (http://news.cnet.com/8301-11128_3-9998606-54.html) FirstSolar is partnering with Sempra Generation, which will own and operate the PV power-plant, being builtnext to their natural gas plant.Stadtwerke Trier (SWT) in Trier, Germany is expected to produce over 9 GWh annuallyA 40 MW system is being installed by Juwi in Waldpolenz Solar Park, Germany. At the time of itsannouncement, it was both the largest planned and lowest cost PV system in the world. The price of 3.25euros translated then (when the euro was equal to US$1.3) to $4.2 per installed watt.[15]

4.8KW of thin film flexible solar panels manufactured by Uni-Solar Ovonic installed on a South Beachhurricane-prone residence in 2008.[16].

Denver-based Conergy Americas and officials at California's South San Joaquin Irrigation District (SSJID)[17]

have installed what is believed to be the world's first single-axis solar tracking system featuring thin-filmphotovoltaic cells.[18]

Time Award

Thin-film photovoltaic cells are included in the TIME's Best Inventions of 2008.[19]

See also


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List of photovoltaics companiesLow-cost photovoltaic cell

Notes^ http://www.renewableenergymagazine.com/paginas/Contenidosecciones.asp?ID=15&Cod=5767&Nombre=PV+solar

1.

^ GBI Research (2011). "Thin Film Photovoltaic PVCells Market Analysis to 2020 CIGS Copper IndiumGallium Diselenide to Emerge as the MajorTechnology by 2020" (http://www.gbiresearch.com/Report.aspx?ID=Thin-Film-Photovoltaic-PV-Cells-Market-Analysis-to-2020-CIGS-Copper-Indium-Gallium-Diselenide-to-Emerge-as-the-Major-Technology-by-2020&ReportType=Industry_Report&coreindustry=ALL&Title=Power_~_Alternative_Energy) .gbiresearch.com. http://www.gbiresearch.com/Report.aspx?ID=Thin-Film-Photovoltaic-PV-Cells-Market-Analysis-to-2020-CIGS-Copper-Indium-Gallium-Diselenide-to-Emerge-as-the-Major-Technology-by-2020&ReportType=Industry_Report&coreindustry=ALL&Title=Power_~_Alternative_Energy. Retrieved 29January 2011.

2.

^ "Amorphes Silizium für Solarzellen"(http://www.ipe.uni-stuttgart.de/content/pdf/Versuch4.pdf) (in German). http://www.ipe.uni-stuttgart.de/content/pdf/Versuch4.pdf.

3.

^ J. M. Pearce, N. Podraza, R. W. Collins, M.M.Al-Jassim, K.M. Jones, J. Deng, and C. R. Wronski(2007). "Optimization of Open-Circuit Voltage inAmorphous Silicon Solar Cells with Mixed Phase(Amorphous + Nanocrystalline) p-Type Contacts ofLow Nanocrystalline Content" (http://me.queensu.ca/people/pearce/publications/documents/t14.pdf) .Journal of Applied Physics 101: 114301.doi:10.1063/1.2714507 (http://dx.doi.org/10.1063%2F1.2714507) . http://me.queensu.ca/people/pearce/publications/documents/t14.pdf.

4.

^ Steve Heckeroth (February/March 2010). ""ThePromise of Thin-Film Solar""(http://www.motherearthnews.com/Renewable-Energy/Thin-Film-Solar-Utility-Scale-PV-Power.aspx) . Mother Earth News.http://www.motherearthnews.com/Renewable-Energy/Thin-Film-Solar-Utility-Scale-PV-Power.aspx.Retrieved 2010-03-23.

5.

^ a b Utility-Scale Thin-Film: Three New Plants inGermany Total Almost 50 MW(http://www.renewableenergyworld.com/rea/news/article/2009/03/utility-scale-thin-film-three-new-plants-in-germany-total-almost-

6.

50-mw?cmpid=WNL-Friday-March13-2009)^ About the Thin Film Partnership Program(http://www.nrel.gov/pv/thin_film/about.html)

7.

^ Yotam Ariel and Coco Liu. "ChineseManufacturers Eye Thin-film PV Market"(http://www.renewableenergyworld.com/rea/news/article/2009/12/chinese-manufacturers-eye-thin-film-pv-market?cmpid=WNL-Wednesday-December16-2009) .http://www.renewableenergyworld.com/rea/news/article/2009/12/chinese-manufacturers-eye-thin-film-pv-market?cmpid=WNL-Wednesday-December16-2009.

8.

^ "ANWELL produces its first solar panel"(http://nextinsight.com.sg/index.php/story-archive-mainmenu-60/36-2009/1480-anwell-produces-its-first-solar-panel) . NextInsight. 2008-09-01.http://nextinsight.com.sg/index.php/story-archive-mainmenu-60/36-2009/1480-anwell-produces-its-first-solar-panel.

9.

^ "Photovoltaics: Thin-film technology about tomake its breakthrough" (http://www.solarserver.de/solarmagazin/index-e.html) . Solar server.2008-08-07. http://www.solarserver.de/solarmagazin/index-e.html.

10.

^ "EPIA projects a rosy picture for the thin filmindustry" (http://social.thinfilmtoday.com/news/epia-projects-rosy-picture-thin-film-industry) . Thin filmtoday. http://social.thinfilmtoday.com/news/epia-projects-rosy-picture-thin-film-industry.

11.

^ "Germany’s largest thin-film pitched roof systembegins production" (http://www.pv-tech.org/news/_a/germanys_largest_thin_film_pitched_roof_system_begins_production/) . PV-tech. 28 October 2008.http://www.pv-tech.org/news/_a/germanys_largest_thin_film_pitched_roof_system_begins_production/.

12.

^ "California Utility to Install 250MW of Roof-TopSolar" (http://www.sustainablebusiness.com/index.cfm/go/news.display/id/15670) .SustainableBusiness.com. 2008-03-27.http://www.sustainablebusiness.com/index.cfm/go/news.display/id/15670.

13.

^ "First Solar announces two solar projects withSouthern California Edison"(http://www.semiconductor-today.com/news_items/2008/JULY/FIRSTSOLAR_170708.htm) .Semiconductor-Today.com. 2008-07-17.http://www.semiconductor-today.com/news_items

14.


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/2008/JULY/FIRSTSOLAR_170708.htm.^ "Report at juwi.de" (http://international.juwi.de/information/press/008PRGridConnectionpartIIofBrandis2008_02.pdf) .http://international.juwi.de/information/press/008PRGridConnectionpartIIofBrandis2008_02.pdf.

15.

^ "Greening Up The House". Miami Herald. April19, 2008.

16.

^ the homepage of the South San Joaquin IrrigationDistrict (http://www.ssjid.com)

17.

^ Conergy Brings World's First Known Thin-FilmSolar Energy Tracking System - and $400,000 InAnnual Utility Bill Savings - to California's SouthSan Joaquin Irrigation District

18.

(http://www.renewableenergyworld.com/rea/partner/conergy-inc-1210/news/article/2009/04/conergy-brings-worlds-first-known-thin-film-solar-energy-tracking-system-and-400000-in-annual-utility-bill-savings-to-californias-south-san-joaquin-irrigation-district?cmpid=WNL-Wednesday-April22-2009)^ "25. Thin-Film Solar Panels"(http://www.time.com/time/specials/packages/article/0,28804,1852747_1854195_1854153,00.html) .Time. 2008-10-29. TIME's Best Inventions of 2008.http://www.time.com/time/specials/packages/article/0,28804,1852747_1854195_1854153,00.html.Retrieved 2010-05-25.

19.

Sources

Grama, S. “A Survey of Thin-Film Solar Photovoltaic Industry & Technologies.” Massachusetts Instituteof Technology, 2008.Green, Martin A. “Consolidation of thin-film photovoltaic technology: the coming decade ofopportunity.” Progress in Photovoltaics: Research and Applications 14, no. 5 (2006): 383-392.Green, M. A. “Recent developments in photovoltaics.” Solar Energy 76, no. 1-3 (2004): 3-8.Beaucarne, Guy. “Silicon Thin-Film Solar Cells.” Advances in OptoElectronics 2007 (August 2007): 12.Ullal, H. S., and B. von Roedern. “Thin Film CIGS and CdTe Photovoltaic Technologies:Commercialization, Critical Issues, and Applications; Preprint” (2007).Hegedus, S. “Thin film solar modules: the low cost, high throughput and versatile alternative to Siwafers.” Progress in Photovoltaics: Research and Applications 14, no. 5 (2006): 393-411.Poortmans, J., and V. Arkhipov. Thin Film Solar Cells: Fabrication, Characterization and Applications.Wiley, 2006.Wronski, C.R., B. Von Roedern, and A. Kolodziej. “Thin-film Si:H-based solar cells.” Vacuum 82, no. 10(June 3, 2008): 1145-1150.Chopra, K. L., P. D. Paulson, and V. Dutta. “Thin-film solar cells: an overview.” Progress inPhotovoltaics: Research and Applications 12, no. 2-3 (2004): 69-92.Hamakawa, Y. Thin-Film Solar Cells: Next Generation Photovoltaics and Its Applications. Springer, 2004.Green, Martin. “Thin-film solar cells: review of materials, technologies and commercial status.” Journal ofMaterials Science: Materials in Electronics 18 (October 1, 2007): 15-19.

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