THIN–FILMSILICONPVTECHNOLOGY
MiroslavZeman
∗
Thin-filmsiliconsolarcelltechnologyisoneofthepromisingphotovoltaictechnologiesfordeliveringlow-costsolarelectricity.Todaythethin-filmsiliconPVmarket(402MWpproducedin2008)isdominatedbyamorphoussiliconbasedmodules;howeveritisexpectedthatthetandemamorphous/microcrystallinesiliconmoduleswilltakeoverinnearfuture.Solarcellstructuresbasedonthin-filmsiliconforobtaininghighefficiencyarepresented.Inordertoincreasetheabsorptioninthinabsorberlayersnovelapproachesforphotonmanagementaredeveloped.Moduleproductionandapplicationareasaredescribed.
Keywords:amorphoussilicon,microcrystallinesilicon,solarcells,photonmanagement
1INTRODUCTION
2THIN–FILMSILICONSOLARCELLSTRUCTURES
Inthelasteightyears(2000-2008)thesolarmoduleproductionhasgrownonaveragebymorethan40%,whichmeansthatthesolarmodulemarketisoneofthefastestgrowingmarketsintheworld(seeFig.1).Thetotalproductionofsolarmodulesreached7910MWpin2008andwasdominatedbycrystallinesilicon(c-Si)solarcells,whichaccountedfor87%ofthetotalproduction[1].Asthec-Sisolarcells,whichrepresentthefirstgenerationsolarcellsforterrestrialapplications,havematured,thecostofthesesolarcellshasbecomedominatedbymaterialcosts,namelythoseofthesiliconwafer,theglasscoverplate,andtheencapsulants.
Onewaytodecreasethecostofsolarelectricityistoreducethethicknessofthesemiconductormaterialsthatformasolarcell.Incomparisontobulkc-Sisolarcells,inwhichthesiliconwaferhasathicknessof200to350micrometers,thetotalthicknessofthesemiconductorab-sorbersinthin-filmsolarcellsislessthanafewmicrome-ters.Thereareseveralsemiconductorsthatareexcellentcandidatesforthin-filmsolarcells,suchassilicon,cop-perindiumgalliumdiselenide(CuInGaSe2=CIGS)andcadmiumtelluride(CdTe).Amongthin-filmsolarcells,asiliconshareinthesolarmodulemarketwasin20085%(ie402MWp)ofthetotalproduction,whiletheshareCdTesolarcellsincreasedtomorethan7%[1].Atpresentmostofthecommercialthin-filmsiliconsolarcellsarerepresentedbyhydrogenatedamorphoussilicon(a-Si:H)basedsolarcells.Adistinctfeatureofthesesolarcellsisthatsiliconbasedlayersaredepositedinalow-temperatureregime(T<600◦C)byplasmaenhancedchemicalvapordepositiontechniques.Sinceinsiliconsolarcelltechnologytheterm“thin-film”usuallycoversarangeof1to100micrometersthicklayers,inthisarticlethin-filmsiliconsolarcellsrefertothelowtemperaturesiliconbasedsolarcells.
In1975WalterSpearandPeterLeComberreportedthatamorphoussiliconhadsemiconductingpropertiesbydemonstratingthattheconductivitycouldbemanip-ulatedbyseveralordersofmagnitudebyaddingsomephosphineordiboranegastothegasmixture[2].Thiswasafar-reachingdiscoverysinceuntilthattimeithadbeenthoughtthatamorphoussiliconcouldnotbemaden-typeorp-typebysubstitutionaldoping.Amorphoussiliconsuitableforelectronicapplications,wheredopingisrequired,isanalloyofsiliconandhydrogen.Therefore,theelectronic-gradeamorphoussiliconisthereforecalledhydrogenatedamorphoussilicon.
Thesuccessfuldopingofa-Si:Hcreatedtremendousinterestinthismaterialfortworeasons.First,thema-terialhadseveralinterestingpropertiesthatopenedupmanyopportunitiesforsemiconductordeviceappli-cations,especiallyinoptoelectronicsandphotovoltaics(PV).Forexample,duetothehighabsorptioncoefficientofa-Si:Hinthevisiblerangeofthesolarspectrum,a1µmthicka-Si:Hlayerissufficienttoabsorb90%oftheusablesolarenergy.Second,theglowdischargede-positiontechnique,alsoreferredtoasplasmaenhancedchemicalvapordeposition(PECVD),enabledproductionofa-Si:Hfilmsoveralargearea(>1m2)andatalowtemperature(100◦Cto400◦C).Thelowprocessingtem-peratureallowstheuseofawiderangeoflow-costsub-stratessuchasaglasssheetandametalorpolymerfoil.Thea-Si:Hcanbesimplydopedandalloyedbyaddingappropriategasestoasilanesourcegas.Thesefeaturesmadea-Si:Hapromisingcandidateforlow-costthin-filmsolarcells.
Today’sthin-filmSisolarcellsarebasedonthesingle-junctionstructure.Thesolarcellstructureissuchthatlightenterstheintrinsica-Si:Hlayerthatservesastheabsorberlayerthroughthep-typelayer.Thisisinordertofacilitatethecollectionofholesfromtheabsorberlayer,whichhavealowermobilitythanelectronsina-Si:H.Therearetwobasicconfigurationsofthin-filmSisolar
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Fig.1.Globalsolarcellproductionbetween2000and2008[1]
Fig.2.Aschematicstructureofasuperstratesinglejunction
a-Si:Hsolarcell
cells,namelyasuperstrateandsubstrateconfiguration,whichdependonthesequenceofthesiliconlayerdepo-sition,p-i-norn-i-p,respectively.Incaseofthesu-perstrateconfiguration,thep-i-ndepositionsequencerequiresatransparentsubstratecarrier.Usually,aglassplatecoatedwithatransparentconductiveoxide(TCO)layerwitharoughsurfaceisusedasthecarrier.Figure2showsatypicalsuperstratesingle-junctiona-Si:Hsolarcell.Thebackcontactisahighlyreflectingmetallayer,usuallydepositedontoaTCOinterlayer,whichisusedtoimprovethereflectionfromthebackcontactbymatch-ingtherefractiveindicesbetweenthen-typesiliconandmetal.Anencapsulantand/oranotherglassplateusuallyformthebacksideofthesuperstratecell.
Incaseofthesubstrateconfiguration,thesubstratecarrierformsthebacksideofthecell.Thisallowstheuseofopaquesubstrates,suchasstainlesssteel.Alsoapoly-merfoilisusedasasubstrate.Sincethepolymerneednotbetransparentatemperatureresistanttypeofpoly-mercanbeapplied,suchaspolyimid.Thefoilscanbethinenoughtobeflexible,whichopensupapossibil-itytoemployaroll-to-rollprocessing.Ahighlyreflect-ingbackcontactwithtexturedsurfacethatconsistsofametallayerofsilveroraluminumandaTCOlayerisdepositedonthecarrier.Thesurfacetextureisrequiredinordertoscatterthereflectedlightbacktothecellattheanglesthatarelargeenoughtofacilitatetotalinter-nalreflection.Afterdepositingthesequenceofthen-i-pa-Si:HbasedlayersaTCOtoplayerwithametalgridisformedasthetopcontact.Thefrontsideofthesubstratecellisfinishedbyatransparentencapsulantlayerwithanadditionalglassplate.Theuseofconductivecarrierssuchasstainlesssteelcomplicatesthemonolithicseriesinterconnectionofcellsonthesubstrate.
Someimportantfeaturesofa-Si:HsolarcellsbecomeapparentfromFig.2.ThefrontcontactlayerisformedbytheTCO.ThetopTCOfilmhastofulfillseveralstrin-gentrequirements,suchashighopticaltransmissioninthespectrumofinterest,lowsheetresistance,temper-aturedurabilityandgoodchemicalstabilityandadhe-sion.InthesuperstrateconfigurationthesurfaceoftheTCOlayerhastobetexturedinordertoenhancelightabsorptioninsidethesolarcellduetothescatteringatinternalroughinterfaces.Thecarriersgeneratedinthep-typelayerdonotcontributetothephotocurrentanditisthusdesirablethatthelightabsorptioninthislayerissmall.Asmallerabsorptionisachievedbyalloyingthea-Si:Hwithcarbon,whichincreasestheopticalbandgaptoabout2eV.Asufficienthighelectricalconductivityisrequiredforbothp-andn-typelayersinordertoformlowresistancecontactswiththeelectrodesandahighbuilt-involtageacrossthep-i-njunction.Theintrinsiclayerwithanopticalbandgapofabout1.75eVservesasanabsorber.Thethicknessoftheintrinsiclayercanvarybetween100to300nm,whichdependswhetheritisin-corporatedinsingleormulti-junctioncells.Becausetheintrinsiclayerissandwichedinbetweenthedopedlay-ers,aninternalelectricfieldispresentacrosstheintrin-siclayer.Theinternalelectricfieldfacilitatesseparationofelectron-holepairsthataregeneratedintheintrin-siclayer.Theelectricfieldstronglydependsonthedefectdistributioninsidetheintrinsiclayerandattheinterfaceswiththedopedlayers.
Thefirsta-Si:HsolarcellwasmadebyCarlsonandWronskiin1976andexhibitedanenergyconversionef-ficiencyof2.4%[3].Inherenttoa-Si:Histhecreationofmetastabledefectswhenthematerialisexposedtolight.ThisisamanifestationofwhatiscalledaStaebler-Wronskieffect[4],whichisundesirableinsolarcells.Theextracreateddefectsintheintrinsiclayeractasrecombi-nationandtrapcentersforphoto-generatedchargecar-riers.Asaresultofthetrappingthespacechargedis-tributioninthelayerchangesanddistortstheinternalelectricfield.Thisleadstoalowerdriftandthustoalowercollectionefficiency.Theperformancedegradationofa-Si:Hbasedsolarcellsduetoilluminationcanbepartlyavoidedbyusingthinnerintrinsiclayersinwhichtheinternalelectricfieldishigherandthereforelesssensi-tivetoanydistortion.However,theemploymentofthin-nerabsorberlayersresultsinalowerabsorption.Theso-lutionforhavingcellswithbetterstabilityistheuseofastackedormulti-junctionsolarcellstructure.Thetotalthicknessofthecompletecellisthesameasforasinglejunctionsolarcell,buteachcomponentcellisthinnerand
JournalofELECTRICALENGINEERING61,NO.5,2010
Fig.3.Aschematicstructureofa)double-junctionandb)triple-junctionthin-filmSibasedsolarcell
thereforelesssensitivetothelight-induceddefects.An-otherwaytominimizetheStaebler-Wronskieffectistodevelopanamorphoussiliconmaterialthatismorestableagainstlightexposure[5].
Theconceptofamulti-junctionsolarcellisalreadywidelyusedinthin-filmsiliconsolarcelltechnology.Inthemulti-junctionsolarcellstructuretwo[6]ormore[7]solarcellsarestackedontopofeachother.Multi-junctionsolarcellapproachmeansthattheabsorberlayerineachcomponentcellcanbetailoredtoaspecificpartofthesolarspectrum.Topcellsefficientlyabsorbshort-wavelengthpartofthespectrum(highenergypho-tons),whereasbottomcellsabsorbtheremaininglong-wavelengthpartofthespectrum(low-energyphotons).Inthiswaythethermalizationlossesareminimized,whichisreflectedinhigheropen-circuitvoltagesofthedevices.Absorberlayersinmulti-junctionthin-filmsiliconsolarcellsarebasedona-Si:H,alloysofa-Si:Hsuchashydro-genatedamorphoussilicongermanium(a-SiGe:H)andhydrogenatedmicrocrystallinesilicon(µc-Si:H).Foratandemcell,thehighestefficiencyispredictedforacom-binationofabsorbermaterialshavingbandgap1.7eVand1.1eVforthetopandbottomcell,respectively.Withabandgapof1.1eVµc-Si:Histheidealmaterialforatandemcellwitha-Si:H.TheUniversityofNeuchˆatelin-troducedamicromorphtandemsolarcellin1994,whichcomprisedana-Si:Htopcellandaµc-Si:Hbottomcell[8].Additionaladvantageisthestabilityofthecompo-nentµc-Si:Hsolarcellagainstlightexposure.Theuse-fulthicknessofµc-Si:Habsorberisintherangeof1.0to3.0micrometers.Inordertoobtaincurrentmatch-ingarelativelythick(above300nm)a-Si:Hlayerisre-quiredinthetopcell,whichstillsuffersfromthelightinduceddegradation.Itisexpectedthatbyimplement-ingimprovedlighttrappingtechniques,especiallyfornearinfraredlight,thethicknessofbothabsorberlayerscan
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bereduced.Thebestlaboratorystabilizedefficiencyofasinglejunctiona-Si:Hcellis10.02%[9],ofatan-demmicromorpha-Si:H/c-Si:Hcellis14.1%(initial)[10]andatriplejunctiona-Si:H/a-SiGe:H/µc-Si:Hcellis11.2%[11],a-Si:H/a-SiGe:H/a-SiGe:Hcellis10.4%anda-Si:H/µc-Si:H/µc-Si:Hcellis12.2%[12].InFig.3aandFig.3batypicaldouble-junctionsiliconsolarcellstructureandatriple-junctionsolarcellstructurearepre-sented,respectively.
Lighttrappingtechniqueshelptocapturelightinthedesiredpartsofasolarcell,whicharetheabsorberlayers,andpreventitfromescaping.Themostimportantroleoflighttrappingistokeepthephysicalthicknessoftheabsorberlayerasthinaspossibleandtomaximizeitseffectiveopticalthickness.Thefollowingtechniquesareusedtotrapphotonsinsidetheabsorberlayer[13]•in-couplingofincidentphotonsatthefrontside,•reflectionatthebackside,
•intermediatereflectorsintandemsolarcells,•scatteringatroughinterfaces,
•scatteringatmetalnano-particles(plasmoniceffects).Tworesearchareascanbedistinguishedregardingthedevelopmentoflighttrappingtechniques.Thefirstareadealswiththemanipulationofphotonpropagationthroughoutasolarcell.Thetechniquesarerelatedtothedevelopmentandimplementationofoptically-activelayerssuchasanti-reflectioncoatings,singleorstackoflayersforindexmatching,intermediateandbackreflec-tors[14].Theselayerstakecarethatphotonsreachtheabsorberlayerandinsidetheabsorberundergomultiplepasses.Thesecondareadealswiththeenhancementofanaveragephotonpathlengthinsidetheabsorberlayer.Thisisachievedbyscatteringoflightatroughinter-facesand/ormetalnano-particles.Thesetechniquesarerelatedtothedesignandfabricationofasurfacetextureonsubstratecarriers.Thesurfacetextureofasubstrateintroducesroughinterfacesintothesolarcellstructure.Scatteringatroughinterfacesprolongstheeffectivepathlengthofphotonsandpartiallyleadstothetotalinternalreflectionbetweenthebackandfrontcontactsconfiningthelightinsidetheabsorber.Recently,layersofmetalnano-particlesandcompositematerialswithembeddedmetalnano-particlesforefficientincouplingandscatter-ingoflightintotheabsorberlayerhaveattractedalotofattention.
Intoday’sthin-filmsiliconsolarcellsthestandardtrappingtechniquesarebasedonscatteringoflightatroughinterfaces,theemploymentofhigh-reflectivelay-ersatthebackcontactsandrefractive-indexmatchinglayers.Theroughinterfacesareintroducedintotheso-larcellbyusingsubstratecarriersthatarecoatedwitharandomlysurface-texturedtransparentconductiveox-ide(TCO)layer,suchasfluorine-dopedtinoxide(FTO)ofAsahiU-typesubstratewithapyramidal-likesurfacestructure(seeFig.4a)andsputteredaluminum-dopedzincoxide(AZO)thatafteretchinginanHClsolutionshowsacrater-likesurfacetexture(seeFig.4b).
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Fig.4.a)Pyramidal-likeandb)crater-likesurfacemorphologyofTCOlayers
Fig.5.Spectralabsorptionina)300nmthicka-Si:Hlayerandb)1µmthickµc-Si:HlayermatchedtotheAM1.5spectrum,whenthe
effectiveopticalthicknessofthelayersisincreased10and50times[13]
3CHALLENGESOFTHIN–FILM
SIPVTECHNOLOGY
ThechallengeinTFSisolarcelltechnologytodayistoincreasethestabilizedconversionefficiency.Futureresearchinvolvesthefollowingareas:
•improvementoftheopto-electronicqualityofa-Si:H,a-SiGe:Handµc-Si:Habsorbers,
•fullunderstandingofmetastablechangesintheprop-ertiesofa-Si:Hbasedmaterialsunderlightexposure,•optimizationofthedopedp-andn-typelayersandtheinterfacesbetweenthedopedlayersandintrinsicabsorbers,theroleofbufferandprofiledlayers,
•developmentoftheTCOfrontmaterialandoptimiza-tionoftheTCO/p-typelayerinterface,
•photonmanagementforeffectiveuseoftheenergyofthesolarradiationandthemaximizationofabsorptionindesiredpartsofasolarcellthatarecalledabsorbers,•increasingthedepositionrateofabsorbermaterialswhilemaintainingtheirquality.
Photonmanagementisoneofthekeyissuesforim-provingtheperformanceofthin-filmsiliconsolarcellsanddecreasingtheproductioncostsbyshorteningde-positiontimesandusinglessmaterial.Theaimofthe
photonmanagementistheeffectiveuseoftheenergyofthesolarradiationandthemaximizationofabsorptionindesiredpartsofasolarcellthatarecalledabsorbers.Pho-tonmanagementinthin-filmsolarcellsisaccomplishedbyanumberoftechniquesthatarerelatedtothefollow-ingareas:
1.effectiveuseofthesolarspectrum,
2.minimizationofabsorptionoutsidetheabsorberlay-ers,
3.trappingofphotonsinsidetheabsorberlayers(lighttrappingtechniques).
ComputersimulationsusingadvancedprogramssuchastheASAprogramfromDelftUniversityofTechnology[15]andtheSunshineprogramfromLjubljanaUniver-sity[16]areavaluabletooltoinvestigatethepotentialofphotonmanagementinthin-filmsiliconsolarcells.Fig.5aand5bshowscalculatedspectralabsorptionina300nmthicka-Si:Hlayerand1µmthickµc-Si:Hlayer,respec-tively,whentheeffectiveopticalthicknessofthelayersisincreased10and50times.Whenmatchingtheabsorp-tioninthelayerstotheAM1.5spectrumonecancalcu-lateapotentialphotocurrentgeneratedinthelayerswhenusedasabsorbersinthin-filmsiliconsolarcells.Increasingtheopticalthicknessofthea-Si:Hlayer10and50times
JournalofELECTRICALENGINEERING61,NO.5,2010
Fig.6.AflexiblemodulefromtheNuonHelianthoscompany[22]
resultsin52%and78%potentialenhancementofthephotocurrent,respectively.Thesimulationsdemonstratethatincaseofµc-Si:Habsorberthelighttrappingplaysevenmoreimportantrole.Increasingtheopticalthick-nessof1µmthickµc-Si:Hlayer10and50timesresultsin90%and138%enhancementofthephotocurrent,de-liveringpotentialphotocurrentof28and35mA/cm2,re-spectively.
4FABRICATIONOFTHIN–FILMSIMODULES
Thin-filmsiliconsolarcellshaveimprovedconsider-ably,capableofachievinginitialefficienciesexceeding15%(tandemmicromorph)[17,18].Basedonthecompa-nies’announcementstheproductioncapacityofthin-filmsiliconphotovoltaicmodulesisexpectedtogrowtoal-most8GWintheyear2010.Thethin-filmsiliconPVmarketisdominatedbyamorphoussiliconbasedmod-ules;howeveritisexpectedthatthemicromorphtandemmoduleswilltakeoverinnearfuture.
Theelectricalpowerdeliveredfromasmallareasolarcellisnotenoughforpracticalapplications.Therefore,solarcellsareconnectedinseriesand/orparalleltoformamodulethatdeliversarequiredpowerandvoltage.Akeysteptopracticalindustrialproductionofa-Si:Hsolarcellswasthedevelopmentofthemonolithicallyintegratedtypeofa-Si:Hsolarcell[19].Monolithicseriesconnectionofcellstomodulesthatcanbeeasilyimplementedinthefabricationprocessisanattractivefeatureofthin-filmSisolarcelltechnology.
Themanufacturingforamorphoussiliconsolarcellsisdividedintotworoutes,processingonglassplatesandprocessingonflexiblesubstrates.Bothmanufacturingap-proachesincludethefollowingmainsteps:•substrateconditioning,
•large-areadepositionofthecontactlayers,ietheTCOasfrontelectrodeandthebackreflectorthatisusuallyadoublelayerofmetalandTCO,
•large-areadepositionofthinSi:Hbasedlayers,
•monolithicseriesconnectionofcells(atpresentappliedonlyformanufacturingonglass)usinglaserscribingofcontactandsiliconlayers,
275
•finalmoduleassemblyincludingencapsulation,apply-ingelectricalconnections,andframing.
Anovelapproachtofabricatea-Si:HmoduleshasbeendevelopedintheNetherlandsintheHelianthosprojectcoordinatedbythemultinationalcorporationAkzoNo-bel[20]andsince2006byNuonHelianthoscompany.TheaimistodemonstratethatflexiblethinfilmsiliconPVmodulesmanufacturedbymeansofautomatedroll-to-rollprocessesofferaversatilelightweightthinfilmsiliconPVproductthatwilloffercompetitivekWhcostsinawiderangeofapplications[21].Theproductiontechnologyisbasedonatemporarysuperstrateconcept,whichcom-binestheadvantagesofbothsuperstrate-andsubstrate-typea-Si:Hsolarcelltechnologies.ThedepositionofahighqualitytopTCOlayerusingtheatmosphericpres-sureCVDandmonolithicseriesintegrationthatoffersthesuperstratetechnologyiscombinedwiththeroll-to-rollprocessingthatisusedinthesubstratetechnology.AnexampleofaflexiblemodulefromtheNuonHelianthoscompanyisinFig.6.
5APPLICATIONS
Duetotheversatilityofthin-filmSitechnologytopro-ducerigidaswellasflexiblemodulesandthehighenergyyield,theapplicationpossibilitiesforthin-filmSibasedmodulesareverybroad.a-Si:Hmoduleshaveasubstan-tiallylowerconversionefficiencytemperaturecoefficientthancrystallinesiliconmodules[23],whichresultsinsu-periorperformanceathigheroperationaltemperatures.Thisfeaturefavourstheimplementationofa-Si:Hmod-ulesinhigh-temperatureconditions.
Theapplicationscoverthefollowingmarketareas:•Consumerelectricityforproductscalculators,wherewatches.smallSmallsolarmodulescellsprovidewithpowerrangingfrom3to50Wpareusedas(portable)batterychargers,incarroofsandavarietyofotherleisureproducts.
•Residentialandcommercialgrid-connectedsystemsthataremainlydesignedforBuilding-IntegratedPho-tovoltaics(BIPV).Themodulesusuallyhavea20-yearpower-outputwarrantyandcanbestructurallyandaestheticallyintegratedasroofingorfaadeele-ments.Takingadvantageofthelasertechniquesthatareappliedduringmanufacturingofa-Si:Hmodules,partlytransparentmodulescanbefabricated.Offer-ingbothenvironmentallyfriendlyperformanceandacompellingdesign,thesetypeofproductsopennewpossibilitiesinBIPVapplications.
•Severallargegrid-connectedsystemshavebeenre-alizedwiththin-filmSibasedmodules.Anexampleistheamorphoussiliconsolarpowerplant(installedpowerof1MWp)thatwascompletedinthebegin-ningof2005intheGermancityofButtenwieseninthesuburbsofMunich.Thepowerplantcomprisesap-proximately10000amorphoussiliconsingle-junctionsuperstrate-typemodules.Theplantisannuallyex-pectedtodeliver1millionkWh.
276
•Off-gridandremote-areaapplicationsincludesolarsystemswitharatedpowerof30to50Wpthataremainlydesignedforlightinginremotehomesandcon-structionsiteswithoutaccesstothepowergrid.Largersystemsaredesignedtogeneratepowerforvillages,remotehomes,waterpumping,telecommunications,trafficcontrolsignals,etc.
•Specialapplications.Thelightweight,flexiblefea-turesofthin-filmsiliconmodulesinconnectionwiththeinherentradiationhardnessandsuperiorhigh-temperatureperformancemakethetechnologyacan-didateforspacePVapplication.
6CONCLUSIONS
M.Zeman:THIN-FILMSILICONPVTECHNOLOGY
[8]MEIER,J.etal:inProc.ofthe1stWPSEC,Hawai,USA,
1994,p.409.[9]BENAGLI,S.—BORRELLO,D.etal:Proc.24thEUPVSEC,
Hamburg,Germany,2009.[10]YAMAMOTO,K.—YOSHIMI,M.etal:Sol.En.Mat.and
SolarCells74(1-4)(2002),449–455.
[11]YUE,G.—YAN,B.—OWENS,J.M.—YANG,J.—GUHA,S.:
Mater.Res.Soc.Symp.Proc.808(2004),808-A09-43.
[12]GREEN,M.A.—EMERY,K.—HISHIKAWA,Y.—WARTA,
W.:Prog.Photovolt.Res.Appl.17(2009),320.
[13]ZEMAN,M.—ISABELLA,O.etal:Mater.Res.Soc.Symp.
Proc.1245(2010),1245-A03-03.
[14]DAGAMSEH,A.M.K.—VET,B.etal:ThinSolidFilms,516
(21)(2008),7844–7850.
[15]ZEMAN,M.—WILLEMEN,J.A.etal:Sol.Energ.Mat.Sol.
C.46(1997),81.
ˇJ.—SMOLE,F.—TOPIC,M.:Prog.Photovolt.Res.[16]KRC,
Appl.11(2003),15.
[17]YANG,J.—BANERJEE,A.—LORD,K.—GUHA,S.:inProc.
ofthe2ndWPSEC,Vienna,Austria,1998,p.387.
ˇJ.:JournalofMaterialsResearch23(4)[18]ZEMAN,M.—KRC,
(2008),889.
[19]KUWANO,Y.—IMAI,T.—OHNISHI,M.—NAKANO,S.:A
HorizontalCascadeTypeAmorphousSiPhotovoltaicCellMod-ule,inProceedingsofthe14thIEEEPhotovoltaicSpecialistConference,1980,p.1408.
[20]MIDDELMAN,E.vanANDEL,E.etal:Proceedingsofthe
2ndWorldConferenceandExhibitiononPhotovoltaicSolarEnergyConversion,vol.I.,1998,pp.816–819.
[21]JONGERDEN,G.J.:MonolithicallySeriesIntegratedFlex-iblePVModulesManufacturedonComodityPolymerSub-strates,inProceedingsofthe3rdWorldConferenceandEx-hibitiononPhotovoltaicSolarEnergyConversion,Osaka,2003,p.6LN-C-05.[22]http://www.nuon.com/nl/het-bedrijf/innovatieve-projecten/
helianthos/index.jsp.
[23]LECHNER,P.—SCHADE,H.:ProgressinPhotovoltaics:Re-searchandApplications10(2002),85–97.
Theflexibilityofthin-filmsiliconsolarcelltechnologytodelivermodulesforalargevarietyofapplicationsisitsmostimportantasset.Thetechnologyhasastrongpotentialtoproducemoduleswithanattractivecost-to-performanceratiogeneratingelectricitywithapricecompetitivetothatofconventionalelectricity.Thecostreductionofthin-filmsiliconmoduleswillbedeterminedbythescalingrateoftheproductioncapacity.Atpresent,thin-filmsiliconsolarcelltechnologyhastoconcentrateonsolvingseveralissueswhicharediscussedinthesectiononchallengesinordertobecomeafullymaturetechnol-ogy.
Furtherdevelopmentofthin-filmsiliconsolarcelltech-nologyingeneralrequiresanincreaseintheperformanceofsolarcells.Onehastorealizethattwothirdsofthepowergeneratedbyapromisingmicromorphtandem(a-Si:H/c-Si:H)solarcellcomesfromthea-Si:Htopcell.Inthenearfuture,attentionwillbepaidtoenhancinglighttrappinginsidethecells,ieimprovingtheTCOma-terialqualityandoptimisingthesurfacetexture.Atthesametime,researchwillcontinueona-Si:Hbasedma-terials,whichhasrecentlyresultedinacompletelynewclassofnano-structuredsiliconfilms.Acknowledgements
TheauthorthanksJanezKrˇcfromLjubljanaUniver-sityforcontributingtothisarticle.
References
[1]PhotonInternational,March2009.
[2]SPEAR,W.—LeCOMBER,P.:SolidStateComm.17(9)
(1975),1193.
[3]CARLSON,D.E.—WRONSKI,C.R.:Appl.Phys.Lett.28
(11)(1976),671.
[4]STAEBLER,D.L.—WRONSKI,C.R.:Appl.Phys.Lett.31
(1977),292.
[5]ZEMAN,M.—’vanELZAKKER,G.—TICHELAAR,F.D.—
SUTTA,P.:PhilosophicalMagazine89:28(2009),2435–2448.[6]FISCHER,D.etal:Proc.25thIEEEPVSC,Washington,DC,
1996,p.1053.
[7]GUHA,S.etal:Proc.PVSEC-15,2005,Shanghai,China,,
p.35.
Received30June2010
ˇMiroslavZemanwasborninZilina,Slovakia,onJune
21,1957.HereceivedthePhDdegreein1989fromtheUni-versityofTechnology,Bratislava,Slovakiaforhisworkonthefabricationofdevicesforelectronicsbasedonamorphoussili-con.Since1989hehasbeenatDelftUniversityofTechnologyintheNetherlandswherehehasbeeninchargeofmorethan30projectsrelatedtothin-filmsiliconsolarcells.In2009hewasappointedafullprofessoratDelftUniversityofTechnol-ogyforthechairofPhotovoltaicMaterialsandDevicesinthedepartmentofElectricalSustainableEnergy.Hisresearchin-terestsarethedevelopmentofnovelconceptsfortheimprove-mentofthin-filmsiliconsolarcellperformance,modelingofdevicesbasedonamorphousandcrystallinesemiconductorsandpracticalimplementationofphotovoltaics.Heisanau-thorandco-authorofmorethan200scientificpublications;contributedtothreescientificbooks,andtogetherwithProf.R.E.I.Schropphewroteabookonthin-filmsiliconsolarcellsthatwaspublishedinUSAbyKluwerAcademicPublishers.***
ThisworkwaspresentedatInternationalConferenceEn-ergetika2010,May18-20,2010,Vysok´eTatry-Tatransk´eMatliare,Slovakia.
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