能量转换与存储原理教学资料multijunction-cell

MultijunctionInorganicSolarCells,Efficiencylimits,Belowbandgapphotonsnotabsorbed,Thermalizationofexcessenergy,Sourcesofenergyloss,CB,VB,IncreasingVOCanddecreasingJSC,Triple-junctioncells,Appl.Phys.Lett.90,183516(2007)EmcoreCorporation,May(2006),WorldRecord:40.7%under240suns!,1.7-1.9eV1.3-1.4eV0.67eV,Thecellsareinseries;currentispassedthroughdeviceThecurrentislimitedbythelayersthatproducestheleastcurrent.ThevoltagesofthecellsaddThehigherbandgapmustseethelightfirst.,CurrentMatching,IndividuallyOptimizedCells,Current-matchedcellsforMJSC,Synopsys,Inc.,February2009,CurrentMatching,Currentlimitedbylowest-currentsubcellTotalVOCisequaltosumofsubcellVOCs,TunnelJunctions,Common3-cellstructure,10-nm-thicklayersofveryhighlydopedsemiconductoroneachsideallowscarrierstotunnelfromconductionbandofn+materialtovalencebandofp+material,/papers/sds/image90.gif,Efficiencyforvarioustopandmiddlecellswhenthesubstrateisgermanium,Baur,C.et.al.,JournalofSolarEnergyEngineering,2007,Latticematching,OnecantunethebandgapoftheIII-VmaterialsbyvaryingtheelementalcompositionToavoiddefects(dislocations),onemustmatchthelatticeconstantsofeachlayer.Forthisreason,itisnotyetpossibletomakeanefficientcellwiththeidealbandgapsshownonthepreviousslide.,C.Bauret.al,Trans.OftheASME,2007,LatticeMatching,LatticeMatchedPreventformationofdislocations,MetamorphicBufferLayerDislocationsterminateinbuffer,Substrate,LMAbsorber,TJ,Absorber,TJ,etc.,BufferLayer,Absorber,TJ,Withmetamorphicmaterials,latticematchingdoesnothavetobeperfect.,Structureof40.7%worldrecordcell,TunnelJunction,R.R.Kinget.al,Appl.Phys.Lett.90,2007,R.R.Kinget.al,Appl.Phys.Lett.90,2007,Latticematchedvs.Mismatched,Thesecellsarehighlyoptimized!,Latticematchedvs.mismatched,40.7%forMMand40.1%forLMat240,135suns(respectively)Latticemismatched(metamorphic)cellstructureArealdefectdensityis8106cm-2Highervoltageuppersub-celluseslargerpartofsolarspectrumMorefreedomtochooseupperandmiddlecellmaterials,R.R.Kinget.al,Appl.Phys.Lett.90,2007,Future-morejunctions,GaInNAsintroducedfor6-junctioncellBandgap1.0eV,latticematchedwithGe.,G.Strobl,etal,IEEE4thworldconf.2,2006,AVeryDifferentApproach,AlanBarnettetal.PROGRESSINPHOTOVOLTAICS:RESEARCHANDAPPLICATIONS,Prog.Photovolt:Res.Appl.2009;17:7583,Thetwosetsofsetsdonothavetobelatticematchedtoeachotherorcurrentmatched.,Summary,HighestefficiencySpace&terrestrialconcentratorCurrentandlatticematchingFutureresearchNewsemiconductorswithidealbandgapsMorejunctionsImprovedtunneljunctions,King,R.NaturePhotonics2,284-