Infoscience

Journal article

Variable light biasing method to measure component I–V characteristics of multi-junction solar cells

We presentanewtechniquetomeasurecomponentcurrent–voltage(I–V) curvesofindividual sub-cellsintegratedinamonolithicmulti-junctionsolarcell.Thisnewapproach,comparedtoall previouslyreportedones,iswellsuitedforthin-filmsiliconp–i–nstructureswheretheso-called shiftingapproximation,whichsupposesthatilluminationonlyshiftsthe I–V curve withoutchangingits shape, isnotvalid.Moreover,theproposedmethodisparticularlyresistanttoproblemsrelatedto electricalshunts.Theprincipleofthismethodliesincouplingthelevelofaselectivelightbiaswiththe level ofmeasuredelectricalcurrentinordertofixthevoltageofaselectedsub-cellwhilesweepingover the currentaxis.Whenoneofthesub-cellshasafixedvoltage,itisthenpossibletogetthe I–V characteristicsofthesecondone,shiftedbyafixedvoltagevalue.Thismeasurementprocedureis simple andrequiresnomodeling.Theaccuracyofthemethodisevaluatedbynumericalsimulationsof a thin-filmsiliconp–i–nphotodiode.Ourtechniqueisthensuccessfullyexperimentallytestedona speciallypreparedthree-terminalamorphous/microcrystallinesilicontandemsolarcell.

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