Crystalline and Polycrystalline Silicon PV relling2/teach/archives/6980.4400.2011/...Crystalline and...

download Crystalline and Polycrystalline Silicon PV relling2/teach/archives/6980.4400.2011/...Crystalline and Polycrystalline Silicon PV Technology ... Typical mono‐and polycrystalline silicon

of 33

  • date post

    06-Feb-2018
  • Category

    Documents

  • view

    220
  • download

    5

Embed Size (px)

Transcript of Crystalline and Polycrystalline Silicon PV relling2/teach/archives/6980.4400.2011/...Crystalline and...

  • CrystallineandPolycrystallineSiliconPVTechnology

    CrystallinesiliconPVcellsareusedinthelargestquantityofalltypesofpanelsonthemarket,representingabout90%oftheworldtotalPVcellproductionin2008.

    The highest energy conversion efficiency reported so far for research crystalline silicon ThehighestenergyconversionefficiencyreportedsofarforresearchcrystallinesiliconPVcellsis25%.

    Standardindustrialcellsarelimitedto1518%withtheexceptionofcertainhighefficiencycellscapableofefficienciesgreaterthan20%.

    HighefficiencyresearchPVcellshaveadvantagesinperformancebutareoftenunsuitable for lowcost production due to their complex structures and the lengthyunsuitableforlowcostproductionduetotheircomplexstructuresandthelengthymanufacturingprocessesrequiredforfabrication.

    Worldannualproductionof PVcellsreachedmorethan7.9GWp in2008(10.6GWp in2009),andtheaverageannualgrowthrateinPVcellproductionoverthelastdecadehasbeenmorethan40%.

    Yet the electrical power generated by all PV systems around the world is less than 0.1%YettheelectricalpowergeneratedbyallPVsystemsaroundtheworldislessthan0.1%ofthetotalworldelectricitygeneration

    T.Saga,NPGAsiaMater.2(3)96102(2010)

  • Typicalmono andpolycrystallinesiliconsolarcells(upper),andsimplifiedcrosssectionofacommercialmonocrystalline siliconsolarcell(lower)(2010Sharp).

    T.Saga,NPGAsiaMater.2(3)96102(2010)

  • ProductionofStandardSiliconPVCells

    Standardcellsareproducedusingone monocrystalline andpolycrystallineborondopedptypesiliconsubstrates.Cellsaretypically125mm(5inches)or156mm(6inches)square,respectively.

    Monocrystalline solarcellsareproducedfrompseudosquaresiliconwafersubstratescutfromcolumningotsgrownbytheCzochralski (CZ)process.

    Polycrystallinecells,ontheotherhand,aremadefromsquaresiliconsubstratescutfrompolycrystallineingotsgrowninquartzcrucibles.Thefrontsurfaceofthecelliscoveredwithmicrometersizedpyramidstructures(texturedsurface)toreducereflectionlossof

    d l hincidentlight.

    Anantireflectioncoating(ARC)ofsiliconnitride(SiNx)ortitaniumoxide(TiOx)isoverlayed onthetexturedsiliconsurfacetofurtherreducereflectionloss.y

    Ahighlyphosphorousdopedn+regionisproducedonthefrontsurfaceofborondopedptypesubstratestoformpn junctions.

    T.Saga,NPGAsiaMater.2(3)96102(2010)

  • Thevaluechainforcrystallinesiliconsolarcellsandmodulesislongerthanthatforthinfilmsolarcells.

    Therearegenerallythreeindustriesrelatedtocrystallinesiliconsolarcellandmoduleproduction:

    (1) metallurgicalandchemicalplantsforrawmaterialsiliconproduction,(2) monocrystalline andpolycrystallineingotfabricationandwaferfabrication

    bymultiwiresaw,and(3) solarcellandmoduleproduction.

    ThecostofPVproductionisroughlydividedinhalfbetweensolarcellmoduleproduction and balanceofsystem fabrication which includes the inverterproductionandbalance of systemfabrication,whichincludestheinverter,cablesandinstallation.

    Thefabricationcostforsolarcellmodulesincludesthecostofthesiliconb (50%) ll i (20%) d d l i (30%)substrate(50%),cellprocessing(20%)andmoduleprocessing(30%).

    Thecostshareisthereforestronglyaffectedbythemarketpriceforpolysiliconfeedstock,andreducingthecostofthesiliconsubstrateremainsoneofthe, gmostimportantissuesinthePVindustry.

    T.Saga,NPGAsiaMater.2(3)96102(2010)

  • ProductionofmetallurgicalgradeSig g

    FromWikipedia

  • 400kgsPurificationbyPhysicalMethods

    FromWikipedia

  • PurificationbyChemicalMethods

    FromWikipedia

  • FromquartzrocktohyperpurepolySi(99.999999999%)

    HemlockSemiconductorGroup (HSC)manufactureshighpuritypolySifeedstock forthep y p ymanufactureofsolarandsemiconductorproducts.HSCsmanufacturingusest i hl il hi h itrichlorosilane,whichisconvertedtopolysilicon inachemicalvapordeposition(CVD)reactoremplying anUrod.Allchemicalsarecapturedandrecycled.

    Impuritiesare1partin1011,intrinsic(i.e.impurity)dopantconcentrationof~1012 cc1,or1 ppt (i.e. 1 part per trillion)1ppt (i.e.1partpertrillion)

    http://www.hscpoly.com/content/hsc_prod/manufacturing_overview.aspx

  • HemlockSemiconductorGroup OwnedbyDowCorningCorporation(63.25%),ShinEtsuHandotai (24.5%),andMitsubishi Materials Corporation (12 25%)MitsubishiMaterialsCorporation(12.25%)

    Beganoperationin1961inHemlock,Michigan

    Leading world supplier of high purity poly Leadingworldsupplierofhighpuritypolycrystallinesilicontothesemiconductorandsolarindustries

    CurrentlycompletingseveralmajorexpansionsinMichiganandTennessee

    36,000metrictoncapacityby2010

    http://www.hscpoly.com/content/hsc_home/default.aspx?bhcp=1

  • T.Saga,NPGAsiaMater.2(3)96102(2010)

  • PolySishortageinmid2000s.

  • TheFloatZoneandCzochralski CrystalGrowthProcesses

    http://www.tf.unikiel.de/matwis/amat/elmat_en/articles/historic_review_cryst_growt.pdf

    W.Zulehner,Wacker Siltronic AG

  • ThinFilmManufacturingSequencePotentially simpler and cheaper, monolithic and flexible

    CrystallineSiliconModules ThinFilmModules

    Potentiallysimplerandcheaper,monolithicandflexible

    CourtesyofBrianKeyes,NREL

    45 60%yieldofSi

    Ref:OverviewandChallengesofThinFilmSolarElectricTechnologies,HarinS.Ullal,Ph.D.,NREL2008

  • ThinFilmsUseLessSCMaterialCourtesy of Brian Keyes, NRELCourtesyofBrianKeyes,NREL

    Amountofmaterialneededfor1kWoutput(moreareaforlessefficiency).

  • Typicalmono andpolycrystallinesiliconsolarcells(upper),andsimplifiedcrosssectionofacommercialmonocrystalline siliconsolarcell(lower)(2010Sharp).

    T.Saga,NPGAsiaMater.2(3)96102(2010)

  • ProductionofStandardSiliconPVCells(cont.)

    Backsurfacep+field(BSF)regionsareformedonthebacksurfacetosuppressrecombinationofminoritycarriers.TheBSFregionsareusuallyformedbyfiringscreenprinted aluminum paste in a belt furnaceprintedaluminumpasteinabeltfurnace.

    Theminoritycarriers(electrons)generatedinthesiliconbulkanddiffusionlayersarecollected by silver contacts (electrodes) formed as gridlines connected by a busbar tocollectedbysilvercontacts(electrodes)formedasgridlinesconnectedbyabusbar toformacombshapedstructure.

    The back contact is usually an aluminum layer which is connected the adjacent cell viaThebackcontactisusuallyanaluminumlayerwhichisconnectedtheadjacentcellviasolderedcopperorprintersilverinterconnects.

    ThefrontcontactisformedusingscreenprintedsilverpasteappliedontopoftheARClayer,withfirethroughtechnology,whichalsoproducestheBSF

    ThescreenprintedfrontsilvercontactpreparedbyfiringtopenetratetheARCisoneofthemostimportanttechniquesforlargevolumefabricationofmoderncr Sicells.

    T.Saga,NPGAsiaMater.2(3)96102(2010)

  • MetallizationfiringofSisolarcellsSimpletoperform,butitinvolvesacomplexsynergismofmanymechanisms:

    (1)dissolutionof(SiN:H)antireflectioncoatingbytheconstituentsoftheAg ink,followedbySiAginteractionsatthefrontcontact;

    ( ) d ff f h d f h f h b lk f h ll f d(2)diffusionofhydrogenfromthe interfaceintothebulkofthecellforimpurityanddefectpassivation;and

    (3)alloyingoftheback Alcontacttoformabacksurfacefield(BSF).

    Sopori etal.

  • Surfacerecombinationcanhaveamajorimpactbothontheshortcircuitcurrentandontheopencircuitvoltage.Highrecombinationratesatthetopsurface particularlyimpact J since the top surface generates a high concentration of carriers LoweringimpactJSC sincethetopsurface generatesahighconcentrationofcarriers.Loweringthehightopsurfacerecombinationistypicallyaccomplishedbyreducingthenumberofdanglingsiliconbondsatthetopsurfacebygrowinga"passivating"layer(usuallysilicondioxide)onthetopsurface.Recombinationatthebacksurfacebecomeinreassingly importantforthincellswithlongminoritycarrierlifetimes.

    animationBSFanimationBSF

    http://pvcdrom.pveducation.org/DESIGN/SURF_MIN.HTM

  • TheindustrialgoalforPVpoweristoreducetheelectricitygenerationcosttog p y gtheequivalentofthatforcommercialgridelectricity.TheenergyconversionefficiencyofsolarcellsisanotherimportantissuebecausetheefficiencyinfluencestheentirevaluechaincostofthePVsystem,frommaterialproductiontosysteminstallation.p y

    Thesolarcellefficiencyislimitedbythethreelossmechanisms:

    photonlossesduetosurfacereflection,siliconbulktransmissionandbackcontactabsorption;

    minoritycarrier(electronsintheregionandholesinthen region)lossdueto recombination in the silicon bulk and at the surface; andtorecombinationinthesiliconbulkandatthesurface;and

    heatingjoulelossduetoseriesresistanceinthegridlinesandbusbars,attheinterfacebetweenthecontactandsilicon,andinthesiliconbulkanddiffusionregion.

    Inthedesignofsolarcellsandprocesses,theselossesareminimizedwithoutloweringtheproductivityofthesolarcells.

    T.Saga,NPGAsiaMater.2(3)96102(2010)

  • Thebasiccellstructureusedincurrentindustrialcrystallinesolarcellsweredeveloped for space and terrestrial use in the 1970sdevelopedforspaceandterrestrialuseinthe1970s:

    lightlydopedn+layer(0.20.3m)forbetterbluewavelengthresponse a BSF formed by a p/p+ low/high junction on the rear side of the cellaBSFformedbyap/p+low/highjunctionontherearsideofthecell arandompyramidstructuredlighttrappingsurface anARCoptimizedwithrespecttotherefractiveindexoftheglueusedto

    adhere toit. Theefficiencyofmonocrystalline cellsforspaceuseisintherangeof14

    16%under1sunAM0testconditions,equivalentto1517%atAM1.5. Thesestandardstructuresforcrystallinesiliconcellsarestillusedin

    standard industrial crystalline cells which offer efficiencies in the range ofstandardindustrialcrystallinecells,whichofferefficienciesintherangeof1417%.

    T.Saga,NPGAsiaMater.2(3)96102(2010)

  • Thekeytechnologiesneededtorealizeefficienciesofhigherthan20%weredevelopedinthe1980sand90s,andthelatesthighefficiencycrystallinesiliconcellspossessmostofthesefeatures(Table1).

    T.Saga,NPGAsiaMater.2(3)96