Sinton-BCT400-BLSI-Bulk-Lifetime-Testing-of-Ingots

BulkLifetimeTestingofIngotsandBricksSintonInstrumentsOutline•Lifetimetheory&background•Eddy-currentmeasurementbackground•EddyCurrentTheory•ComparisontoMicrowavePCD•BCTInstrument•Hardwareoverview•Softwareoverview•InstrumentUse&SEMIPV13•Maintenance&Calibration•Troubleshooting•StandardSettings•P-typeCZ•P-typeMulti•N-typeCZ2LifetimeTheory•Carrierlifetime(τ)is:•Averagetimeforexcesscarriertorecombine•Determinesdiffusionlength•Highlifetimeneededforhighefficiency•Lowlifetimecausedby:•MetallicImpurities:•Fe,Cr,Al,Au,Cu,others•OxygenContamination:•B:Opairs,OxygenPrecipitates•CrystallineDefects:•Dislocations,grainboundaries3DLSolarCellOperation•Cellperformancedependsonlifetime.•Higherefficiencycelldesignleadstohighersensitivitytobulklifetime451015202510100100010000CellEfficiency(%)BulkLifetime(microseconds)PC1DSimulationofIBCCell111315171101001000CellEfficiency(%)BulkLifetime(microseconds)PC1DSimulationStandardProductionCellEddyCurrentLifetimeMeasurement•Eddy-currentsensormeasuresconductance•IR-passfilteredxenonflashlampgeneratescarrierswithwavelengths850nmto1200nm•ResistivityandLifetimearecalibratedmeasurementsofphysicalparameters•Lifetimecalculatedintwomodes:•Quasi-Steady-StatePhotoConductance(QSSPC)•TransientPhotoConductanceDecay(TransientPCD)•SEMIPV13standarddescribesmeasurement5MeasurementTheory-QSS•Quasi-Steady-State(QSSPC):•Flashdecaytime(200Wsmode)is~2.2ms•Suitableforlifetimeslessthan200µs6GnQSSSiflash00.050.10.150.20.250.30.3501020304050600.0E+005.0E-031.0E-021.5E-02PhotoconductanceIlluminationTimeQSSPC•Requiresestimateofphotogeneration(G)insample•GcalculatedfromreferencecellsignalMeasurementTheory-Transient•TransientPCD:•Xenonflashcutofftime~50µs•Suitableforlifetimesgreaterthan100µs7dtndntrans0.000.050.100.150.200.250.300.350.400.450501001502002503003500.0E+001.0E-032.0E-033.0E-034.0E-035.0E-03PhotoconductanceIlluminationTimeTransientPCDflashSiComparingwithothermethodsMethodHowisexcesscarrierdensitysensed?Issues:Pros/ConsRF-QSSPCEddycurrentsensingofPhotoconductanceConversiontoΔnusingknownmobilityfunctionSimplecalibrationthatisvalidforawiderangeofsamples.Real,physicallifetimeresult.Requiresmobilityandphoto-generationcalculationormeasurement.LowresolutionRFTransientEddycurrentsensingofPhoto-conductance.ConversiontoΔnusingknownmobilityfunction.Simplecalibration.Measuresreal,physicallifetime.CanbesubjecttotrappingandDRMartifactsatlowcarrierdensity.µ-PCD/MDPMicrowavereflectanceorabsorptionsensingofphotoconductance.High-resolutionmappingcapability.Non-lineardetectionofphotoconductanceinsomeinjection-levelordopantranges,skin-depthcomparabletosamplethicknessinsomecases.DRMandtrappingartifactsatlowcarrierdensity.Doesnotmeasurephysicalparameter.8MicrowavePCD•MicrowaveSensor:•Shortwavelengthillumination(905nm)•Sensorisnon-linearandnotcalibrated•PV9Standard:•“Therefore,thistestmethoddoesnotpurporttomeasureexcesscarrierlifetime…”(SEMIPV9-1110,)•“…theresultofthistestmethodisnotarealphysicalpropertyofthetestspecimen…”(SEMIPV9-1110,)•“Themethodisnotsuitableformeasurementsinbricksoringotswherethedecaytimeisgreaterthan10µsduetothediffusionofcarriersintothematerialbeyondthemeasurementdepthofthemicrowavesused”(SEMIPV9-1110,)9InvalidMicrowavePCDMeasurement(High-injectionconditions)300micron-thickwafer,2ohm-cmwafer,2.5x1015photon/cm2laserpulseClearly,themicrowavesignalISNOTLINEARINPHOTOCONDUCTIVITYovertherangeofphotoconductivity(15(ohm-cm)-1)producedbya2.5x1015cm-2laserpulse.ThismeasurementresultisNOTvalidas“carrierrecombinationlifetime”forthiswaferwiththislaserpulse.1.253.255.257.259.2511.2513.25051015MicrowaveReflectanceSignal(Volts)Conductivity(Ohm-cm)-12.5x1015photons/cm2=15(ohm-cm)-12ohm-cmIfmicrowavesignalwerelinearinconductivityActualmicrowavesignalbasedonfittodata.12Xerror!ComparisonChartFeature/ParameterEddyCurrentQSSPC,TransientPCDMicrowaveµPCDMeasurementAreaAreaAverage(10-40mm)1mmSensorDepthSensitivity3000µm100-1000µmIlluminationWavelength1000nm(effective)905nm(typical)IlluminationAbsorptionDepth100-5000µm30µmLifetimeMeasurementRange(BulkSamples)0.1µs-15000µs10µsSensorSaturationLifetime(UnpassivatedBulkSamples)10000µs~8µsCalibratedConductanceSensorYesNoReal,PhysicalParameterMeasurementYesNoInjectionDependentLifetimeMeasurementYesNoCalibratedEmitterSaturationCurrent(Joe)MeasurementYesNoExtensiveTechnicalResearchDatabaseforPVindustryYesNoAccurateMeasurementwithoutSurfacePassivationYesNoResultsReproducibleandComparableBetweenUsersYesNoDesignedForPVIndustryYesNo11BCT-400Instrument•HardwareOverview•SoftwareOverview•BestPractice,SEMIPV13,SEMIAUX-017•Maintenance•Troubleshooting12BCT-400MeasurementHead13•GreenLEDindicatesthatinstrumentpowerison•RedLEDindicatesifheaterison(raisesinstrumenttemperaturetostable28C)•Instrumentshouldwarmupfor30minutesbeforeuse•CanbeleftONatalltimes,donotleaveonlargeblockofSi•Flashbulbfitsintoremoteflashhead•Neverhandleflashbulbwithbarehands,seeusermanualforinstructionsonhowtoreplace.FlashPowerSupplyStack&X5D•3pieces,toptobottom:•Qpaq-X•PXC•PR-