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1、phys.stat.sol.(a)204,No.7,2190–2195(2007)/DOI10.1002/pssa.200675436ElectronicactivityofSiCprecipitatesinmulticrystallinesolarsilicon*,112JanBauer,OtwinBreitenstein,andJean-PatriceRakotoniaina1MaxPlanckInstituteofMicrostructurePhysics,Weinberg2,06120Halle,Germany2Q-CellsAG,Guardianstraße16,06766Th
2、alheim,GermanyReceived17September2006,revised23April2007,accepted24April2007Publishedonline3July2007PACS72.80.Jc,73.40.Lq,84.60.JtIntheupperpartofblock-castmulticrystallinesilicononeoftenfindssiliconcarbideandsiliconnitrideprecipitatesandinclusions.Thesecontaminantscancausesevereohmicshuntsinsola
3、rcellsandthusde-creasetheefficiencyofthesolarcellsverystrongly.Itiswellknownthatthesiliconcarbideprecipitatescausetheohmicshunts.However,theelectricalpropertiesofthesiliconcarbidewasunknownsofar.Tostudytheelectricalpropertiesofthesesiliconcarbideparticlesweisolatedthemfromthesiliconbulkma-teriala
4、ndperformeddifferentelectricalmeasurementsonthem.Themeasurementsshowthatthesiliconcarbideprecipitatesarehighlyconductive.Aninvestigationoftheheterojunctionsilicon–siliconcarbidewasalsoperformedandasimulationofthisheterojunctionleadstoanewmodeloftheohmicshuntmechanism.Itisconcludedthattheshuntcurr
5、entflowsinsideofthefilaments.©2007WILEY-VCHVerlagGmbH&Co.KGaA,Weinheim1IntroductionTheefficiencyofmulticrystallinesiliconsolarcellscanbestronglyreducedbymaterial-inducedshunts[1].Theseshuntsarecausedbysiliconcarbide(SiC)precipitates[2],whichweregeneratedduringthecrystallisationofthemulticrystalli
6、nesilicon(mc-Si)ingotattheblock-castingprocess[3].Itiswellknownthatso-calledSiC-filamentscausedangerousohmicshuntsinsolarcells[2].However,theelec-tricalpropertiesandtheelectronicactivityoftheSiCparticles,whichareembeddedinthemc-Si,wereunknownsofar.SincetheSiC-filamentscanhavealengthuptosomemillim
7、eters,theycandamageseveralsolarcellwafers,anditwillbeimportanttoknowmoreabouttheshuntingmechanism.ThispaperconcentratesontheelectricalmeasurementsoftheSiC-filamentsandtheelectronicactivityoftheseprecipitatesinthemc-Sib