59Battery Handbook Chapter 35-第8页
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59Battery Handbook Chapter 35-8
34.36CHAPTERTHIRTY-FOUR；34.4.2PolymerElectrolyte；Thepolymerelectrolytelit；Figure34.9showsaschemati；Theearlybatteriesusedpol；Thesolidpolymerelectroly；34.4.3LithiumBatteriesUs；Inthel
34.36CHAPTERTHIRTY-FOUR34.4.2PolymerElectrolyteCellsThepolymerelectrolytelithiumbatteriescontainallsolid-statecomponents:lithiumastheanodematerial,athinpolymer?lmasasolidelectrolyteandseparator,andatransitionmetalchalcogenideoroxide,orasulfur-basedpolymerasthecathodematerial.Thesefeaturesofferthepotentialforimprovedsafetybecauseofthereducedactivityoflithiumwiththesolidelectrolyte,?exibilityindesignasthecellcanbefabricatedinvarioussizesandshapes,andhighenergydensity.Figure34.9showsaschematiccrosssectionofasolidpolymerelectrolytecell.Thecathodeandelectrolytearecoatedontoacurrentcollectortoformathinsheet,calledthecathodelaminate.Thelithiummetalfoilisappliedtothecathodelaminatetoformalayeredstructure,withthesolidpolymerseparatingthelithiumfromthecathode.Thesecellsaredesignedinextremelythincomponentswithhighsurfaceareastominimizetheinternalresistanceandcompensateforthelowerconductivityofthepolymerelectrolyte.Thethick-nessdependsonthespeci?ccelldesignandrequiredcapacity.Athickerlaminatedeliversahighercapacityperunitareaofelectrode,butwithloweref?ciencyatthehighercurrentdrains.43Theearlybatteriesusedpolyethyleneoxide(PEO)-basedelectrolytescontainingalithiumsalt,whichhaveanappreciableconductivityatabout100?Cbutlowconductivityatroomtemperature.Laternewpolymericelectrolytematerials,suchasPEOcopolymers,PEOblends,plasticizedPEOelectrolytes,andgelledelectrolytes,withbetterconductivityweredeveloped.SomeofthecathodematerialsinvestigatedforthesebatteriesareTiS2,VOx,V2O5,LixCoO2andsulfur-basedpolymers.Thesolidpolymerelectrolyte(SPE)batteryhasbeenconsideredforawiderangeofapplications,fromsmallportableelectronicsuptoandincludingelectricvehicles.34.4.3LithiumBatteriesUsingPEO-basedElectrolytesInthelate1970s,polymerelectrolytematerialswereproposedforuseinsolid-statebatterydesigns.44Aconsiderabledevelopmentefforthasresultedinanumberofreviewarti-cles45C47describingthestatusofsuchbatteriesinsomedetail.Theuniqueaspectofthesebatteriesisthattheelectrolyteisasolid?exible?lmcomprisedofapolymermatrixandanionicsaltcomplexedintothematrix.Thin-?lmsolid-polymerelectrolytebatteriesofferthepossibilityofanintrinsicallysafebatterydesignincombinationwithgoodhigh-ratecapa-bility.Polyethyleneoxidewasthe?rstmaterialutilizedasthematrixmaterial.Initially,itwasnecessarytooperatethecellsatelevatedtemperatures(100?C)toobtainadequateconduc-tivities(10?3S/cm),butavarietyofpolymericelectrolytesthatmaybeusefulatnormalambienttemperaturesweresubsequentlydeveloped.Thispolymerelectrolytebatteryisbasedonthin-?lmcomponentsthatincorporatelargeareaelectrolyteandelectrodelayers.Agen-eralcellcanbeschematizedas:Lix?A?/Li?ion-conductor/Liz?B?whereLix?A?isametalliclithiumanodeoralow-voltagelithium-intercalationanode(neg-ativeelectrode),theLi?ionconductorisalithiumsalt-polymercomplex,andLiz?B?isahigh-voltagelithium-intercalationcathode(positiveelectrode).Usually,thepolymercom-ponentoftheelectrolytelayerisalsothebinderfortheelectrodelayers.Inaddition,theRECHARGEABLELITHIUMBATTERIES(AMBIENTTEMPERATURE)34.37polymercomponentmaybegelledbytheadditionoflowmolecularweight(liquid)solventstoenhanceitsionicconductivity.Suchabatterysystemshowstwomajoradvantageswithrespecttostandardbatteriesthatuseinertporousseparators:1.Theelectrodeandelectrolytelayersarelaminated(usuallybyheatingandpressingthelayers),thusallowingvariousbatteryshapeswithoutlossofcontact.2.Evenifalowmolecularweight(liquid)plasticizerisaddedtoobtainhighconductivityatambientandsub-ambienttemperatures,thereisnofreeliquidpresentinthebatterythuspreventinganyleakageproblems.ExamplesofthebatterysystemsunderdevelopmentoravailableonthemarketplaceareindicatedinTable34.16.Theycanbeconvenientlyclassi?edintothreecategories:1.Positiveandnegativeintercalationelectrodes(lithium-ion)withagelledpolymerelectro-lyte(PEO-based).2.Positiveandnegativeintercalationelectrodes(lithium-ion)withaporouspolymersepa-ratorlayer?lledwithaliquidelectrolyte(PVDF-based).3.Positiveintercalationelectrode-lithiumanode(lithium-metal)withadrypolymerelectro-lytelayer.The?rstandthesecondcategories,thelatterofwhich(PVDF-basedsystems)doesnotproperlybelongtotheclassofpolymerelectrolytebatteries,arecoveredinChap.35.Inthischapter,theattentionisfocusedonthelithiummetal,drypolymerelectrolytesystems.Thesearchforhighenergydensitybatteries,especiallyforelectricvehicleapplications,hasledtotheconsiderationoftheuseoflithiummetalanodes.Nootheranodecanattainthesameelectrochemicalperformanceintermsofspeci?cenergyasmetalliclithium.How-ever,safetyissuesaswellaspoorcyclelifeperformancehavepreventedthecommercialsuccessoflithium-metalbatterieswiththeexceptionofprimarybatteries.Atthepresenttime,therearethreemajorprogramsaimedatthedevelopmentoflithium-anode,dry-polymerelectrolytebatteriesforelectricvehicles(Table34.17).WithintheseR&Dprograms,sub-stantialsuccesseshavebeenobtainedintermsofcyclabilityofthelithium-polymerelectro-lyteinterface51aswellasthewholebatterysystem.50However,Argotech’sbatteryNPS-24V80(Table34.18)appearstobetheonlysystemclosetocommercialization.Thisbattery,designedfortelecommunicationapplications(especiallyforoutsideplants),isafall-outoftheEVbatterymoduledevelopedwithintheUSABCprogram.Figure34.21illustratestheinternaldesignofthelithiumpolymercell.Thecellismadebylaminating?vethinlayersincludinganinsulatinglayer,alithiumfoilanode,asolidpolymericelectrolyte,atransitionmetaloxidecathode(VOx)andacurrentcollector.Theunitcellismadebywindingthelaminated?lmintoajellyroll(asinFig.34.21)ora?atroll(preferredformultiplecellbatteryassembly)structure.Thesecellsarethenassembledinseriesandinparallelarrangementstoformmodulesofdifferentsizesandshapesfornumerousapplications.Asanexample,Fig.34.22illustratesthedesignofalithium-polymerbatterymoduleforelectricvehicleapplications.Unitlaminatedcellsarepackagedintoastackof?atcellstocreateamodule.Thecellscanbeconnectedinparalleland/orseriesarrayswithinasinglecontainertobuildthedesiredmodulecapacityandvoltage.Thepack-agingalsoprovidesthemechanical,electrical,andthermalcontrolsrequiredforoperation.Eachmoduleisafullyfunctionalbatterysystem,includingintelligentcontrolandmonitoringelectronicsthatinterfacewiththebatterypackcontroller.RECHARGEABLELITHIUMBATTERIES(AMBIENTTEMPERATURE)34.39TABLE34.17MajorLithiumMetalAnode,DryPolymerElectrolyte(PEO-based),BatteryTechnologyDevelopmentProjects(fromRef.50)SponsorUSABC(USA)Bollore′Tech.EDF(France)MICA-MURST(Italy)ProjectleadersIREQ-3M-ANLCEREMENEACathodeVOxVOx,LiyMnOxVOx,LiyMnOxApplicationEVEVEVStatus2.4kWhprototypesPrototypesScaling-upto1kWhprototypesTABLE34.18Speci?cationsofArgo-Tech’sBatteriesfromRef.49NPS-24V80NominalvoltageRatedcapacityRatedenergyMaximumdischargecurrentFloatvoltageEnergydensitySpeci?cenergyLengthWidthHeightVolumeWeightAmbientoperatingtemperatureStoragetemperatureFloatlifeat40?CCyclelifeat60?C(80%DOD)24V/Module2.65V/Cell80Ah(@C/8)1.9kWh(@C/8)20A27.9V/Module3.1V/Cell110WhL?197Whkg?mm251mm17.4dm319.9kg?40to65?C?40to65?COver10years200cyclesEVmodule20V119Ah(@C/3)2.4kWh@C/3)365AN/A220WhL?1155Whkg?1Applicationspeci?cApplicationspeci?cApplicationspeci?cca.11dm315.7kgN/AN/AN/A600cyclesFIGURE34.21Laminatedlithium-polymerelectrolytecellassembly.(FromtheProceedingsofEVS16,reprintedbypermissionofthepublisher,EVAAP.)34.40CHAPTERTHIRTY-FOURFIGURE34.22DesignofaLithiumPolymerBattery(LPB)moduleforEVapplications.Themoduleincludesanenclosurewhichprovidesmechanicalsupportandthermalinsulationalongwithcontrolhardwareandvehicleinterfaces.(FromtheProceedingsofEVS16,reprintedbypermissionofthepublisher,EVAAP.)Thespeci?cationgivenforthestationaryapplicationNPS-24V80batteryaregiveninTable34.18andcomparedwiththeparentEV-module.AtypicaldischargecurveisdepictedinFigure34.23.Thebatteryisabletodeliver80Ahcapacityata10Adischargerateina60?Ctemperatureenvironment.Theexcellentperformanceathighambienttemperatureisoneofthemajoradvantagesofthissystem.Theunitcellsoperateat40to60?C,anddonotcontainanyliquid:Thebatteryisdesignedtohavenodegradationinnon-ventilatedandwarmenvironments(forexample:telecommunicationcenters).Itcontainsnoliquid,thusitishermeticallysealed,anddry-outduringoperationandliquidleakageareimpossible,andthereforenomaintenanceisrequired.Inaddition,thebatteryshowsverygoodsafetychar-acteristics.Overchargingtestsshowednogasgeneration.53Oncemore,noliquidleakageispossibleevenwhenthemoduleisaccidentallycrushed.Finallyandmostimportant,waterimmersiontestsonentirecrushedcellsshowedonlyaveryslowreaction.包含各类专业文献、专业论文、生活休闲娱乐、高等教育、文学作品欣赏、行业资料、59Battery 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CONTENTS；1.1；1.2；1.3；1.4OrganicLight-Emitting；1.4.1Dual-FunctionPolyme；1.4.2PolymerLight-Emitti；1.4.3PLEDwithStableCatho；1.4.4PLEDandPLECinSurfac；1.4.5OptocouplersMadewit；1.5Flat-P
1CONTENTS1.11.21.31.4OrganicLight-EmittingDevicesandTheirApplicationsforFlat-PanelDisplaysGangYuandJianWangIntroduction................................................................................................................ConjugatedPolymersinPLEDs.................................................................................PLEDStructures,Processes,andPerformance...........................................................NovelDevicesandNovelFunctionsinThin-FilmPolymerDevices..........................1.4.1Dual-FunctionPolymerDeviceandDisplayMatrices....................................1.4.2PolymerLight-EmittingElectrochemicalCells................................................1.4.3PLEDwithStableCathodeElectrode..............................................................1.4.4PLEDandPLECinSurfaceCellConfiguration.............................................1.4.5OptocouplersMadewithSemiconductingPolymers........................................1.5Flat-PanelDisplaysMadewithSolution-ProcessibleOrganicSemiconductors.........1.5.1SMOLEDsandPLEDsasEmitterElementsinFlat-PanelDisplays..............1.5.2PMOLEDDisplaysversusAMOLEDDisplays..............................................1.5.3MonochromeAMPLEDsMadewithSolution-ProcessiblePolymers.............1.5.4Full-ColorAMPLEDModules........................................................................1.5.5PerformanceSimulationforFull-ColorAMOLEDs.......................................1.5.6AMOLEDforGraphicandMotionPictureApplications...............................1.6SummaryandRemarks..............................................................................................Acknowledgment.................................................................................................................References...........................................................................................................................1.1INTRODUCTIONTheelectroluminescence(EL)phenomenonwasfirstdiscoveredinapieceofcarborundum(SiC)crystalbyH.J.Roundin1907[1].Commercialresearchintolight-emittingdiodes(LEDs)technologystartedinearly1962,whenNickHolonyakJr.createdthefirstinorganicLED[2,3].Workongalliumarsenidephosphide(GaAsP)ledtotheintroductionofthefirstcommerciallymass-produced655nmredLEDsin1968byHewlett-PackardandMonsanto.In1950s,BernanosefirstobservedELinorganicmaterialbyapplyingahigh-voltagealternatingcurrent(AC)fieldtocrystallinethinfilmsofacridineorangeandquinacrine[4,5].Thedirectcurrent(DC)drivenELcellusingsinglecrystalsofanthracenewasfirstdemonstratedbyPopeandhiscoworkersfollowingthediscoveryofLEDsmadewithIIICVcompoundsemiconductors[6].In1975,thefirstorganicelectroluminescence(OEL)devicesmadewithapolymerpolyvinylcarbazole(PVK)weredemonstrated[7].InearlyattemptstodeveloporganicELdevices,thedrivingvoltagewasontheorderof100Voraboveinordertoachieveasignificantlightoutput[8C10].Vincettetal.achievedanoperatingvoltagebelow30Vbyusingathermallydepositedthinfilmofanthracene[11].TheresearchfocusedmainlyintheacademicfielduntilDr.C.W.TangandhiscoworkersatKodakChemicalshowedforthefirsttimeefficientorganiclight-emittingdevicesinmultilayerconfigurationwithsignificantperformanceimprovement[12].Nowadays,smallmoleculeorganiclight-emittingdiodes(SMOLEDs)madebymeansofathermaldepositionprocesshavebeenusedforcom-mercial display products. Pioneer Corporation has commercialized OEL display panels forconsumerelectronicsapplications,suchascaraudiosystems,CD=MP3players,A=Vreceivers,etc.,since1999.OneoftherecentproductsfromPioneerElectronicsisanin-carCDplayerfeaturingablueOELdisplaymadeinpassivematrix(PM)configuration[13].KodakCompanyandSanyoElectricCompanyLimiteddemonstratedthefirstfull-color2.4-in.activematrix(AM)SMOLEDdisplaysin1999.Theirjointmanufacturingventure,SKDisplayCorporation,producedtheworld’sfirstAMSMOLEDdisplaysforaKodakdigitalcamera(ModelLS633)[14].Recently,SonyCorporationannouncedmassproductionofSMOLEDdisplaysforitsCLIEPEG-VZ90personalentertainmenthand-helddevices,startinginSeptember2004[15].Anothertypeoforganicsemiconductor,conjugatedpolymer,wasdiscoveredin1977byAlanJ.Heeger,AlanG.MacDiarmid,andHidekiShirakawa[16,17].Inadditiontothefocusonitsnovelphysicalandchemicalpropertiesinheavilydopedstates,greatattentionwaspaidtoitsintrinsicpropertiesintheundopedsemiconductingphase,itsnonlinearopticalproper-tiesunderphotoexcitation[18,19]anditsinterfacialbehaviorswithmetalcontacts.SchottkydiodesmadewithpolyacetylenefilmweredemonstratedinmetalCsemiconductorpolymerCmetalconfigurations[20,21].Theiroptoelectricandelectro-opticalpropertieswerestudied.Althoughsignificantphotosensitivitywasdemonstrated,theelectroluminescentpropertyofthissystemwasintrinsicallyweakduetoitselectronicstructure.Extensivestudiesofconjugatedpolymersintheearlyandmiddle1980sfocusedonsearchinganddevelopingnewmaterialswithsolutionprocessibility.Apopular,well-studiedsystemwasapolythiophenederivative,ofwhich poly(3-alkyl)thiophene (P3AT) was one (Figure 1.1). Solution-processed metal =P3AT =metalthin-filmdevicesweredemonstratedattheUniversityofCaliforniaatSantaBarbarain1987[22].Followingthefirstdemonstrationoflight-emittingdevicewithunsubstitutedpoly( p-phenylenevinylene) (PPV) (Figure 1.1) by R.H. Friend’s group at Cambridge University,[23]ahighefficientpolymerlight-emittingdiode(PLED)devicewasmadewithasolution-processiblepolymer,poly[2-methoxy-5-(2’-ethyl-hexyloxy)-1,4-phenylenevinylene](MEH-PPV)(Figure 1.1), by Heeger’s group in Santa Barbara, California [24]. As discussed in laterchapters,thecurrentcommercializedsolublePPVderivativesarebasedonasynthesisapproachoriginallydevelopedbyFredWudl’sgroupinSantaBarbarain]andlatermodifiedbyUNIAXCorporationinthemid-1990sandAventisResearch&Technolo-giesGmbH(nowCovionOrganicSemiconductorsGmbH)inthelate1990s.SolublePPVderivativessynthesizedfollowingthisapproachnotonlyhavehighmolecularweights,butalsoshowexcellentsolubilityincommonorganicsolvents.Mostimportantly,thesematerialshaveintrinsicallylowchargedimpurity(typicallybelow1014percm3)andhighphotolumi-nescentefficiency(typicallyintherangeof20C60%)[25C28].PLEDsmadewithsuchPPVfilmsshowhighelectroluminescentefficiency,lowoperationvoltage,andlongdevicelifetime[29C31].DisplaysmadewithPPVemitterswerefirstcommercializedin2002byPhilips(Norelcoelectricrazor:Spectra8894XL).AlthoughtheenergygapinaPPVderivativecanbeincreasedbyreducingconjugationandplanarizationbetweenthephenylgroupandthevinylgroup(asobservedinPPVswithphenylgroupsattachingat2or5positionsorbothsites)[27,32,33],itisnotlargeenoughtoproducesaturatedbluecolorneededforfull-colordisplays.ConjugatedpolymerswithopticalPolyacetylene(PA)Polythiophene(PT)nPoly para-phenylenevinylene(PPV)nnOR1RPoly(3-alkyl)thiophene(P3AT)(R-methyl, butyl, etc.)Polypyrrole(PPy)Poly(2,5-dialkoxy)paraphenylenevinylene(e.g., MEH-PPV)R2OnnNnPoly para-phenylene(PPP)R2nPolyisothianaphthene(PITN)nLadder-typepolyparaphenylene(LPPP)R1R1Poly ethylenedioxythiophene(PEDOT)Polyparaphenylenesulphide(PPS)R2SnnAlkoxy-substitutedpoly para-phenylene vinylene(MEH-PPV)Polyheptadiyne(PHT)nnOPoly(3-hexyl) thiophene(P3HT)SnPolyaniline (PANI)NN..nnPolyfluorene (PFO) RRFIGURE1.1Molecularstructuresofpopularconjugatedpolymers.energygaps(&2.9eV)areneededforPLEDswithblueemission.Significanteffortshavebeenmadeonsearchinganddevelopingwideenergygappolymers(suchaspoly(p-phenyl)andtheirfunctionalderivatives)[34C46].Inadditiontoitsuseasmakingblueemitters,thesamebuildingblockscanalsobeutilizedformakingredandgreenemitters(asthehost)bycopolymerizingthemwithaproperemittergroup(astheguest)[47C49].Thered,green,andbluematerialsetsdevelopedbyseveralcompanies(includingCovionandDowChemical)areallsolubleincommonorganicsolventswithhighoptoelectricperformanceandgoodfilm-formingproperties[49,50].PLED-baseddisplaysareattractiveduetotheirprocessingadvantagesindevicemanufac-ture.Theorganicmaterialsusedaresolubleincommonorganicsolventsorinwater.Large-sized,uniform,andpinhole-freethinfilmscanbecastfromsolutionsatroomtemperaturebymeansofspincoatingorothercoatingtechniquescommonlyseeninprintingandpaintingindustries.Becauseofthelargeelongationatrupturecharacteristicofpolymers,theyareflexibleandcanbeeasilyfabricatedontorigidorflexiblesubstratesinflatorcurvedshapes.Solutionprocessingisalsopromisingforformingpatternedcolorpixelsinfull-colordisplays.DifferentELpolymerscanbedepositedontopredefinedlocationsbymeansofaprintingtechnique,suchasinkjetprinting[51,52],screenprinting[53,54],orphotolithographicpatterning[55].Full-colorPLEDdisplaysmadewithaninkjetprocessorlaser-inducedthermaltransferprocesshavedemon-stratedexcellentimagequalities[56,57].Section 1.2 gives a brief review of conjugated polymers in semiconducting and metallicphases. Section 1.3 discusses device architectures and their corresponding processes. Section1.4 introduces some novel devices and their functions in thin-film polymer devices. Section 1.5isdevotedtotechnicalmeritsofSMOLEDsandPLEDsusedasemitterelementsinflat-paneldisplays.1.2CONJUGATEDPOLYMERSINPLEDSConjugatedpolymersrepresentanovelclassofsemiconductorsthatcombinetheopticalandtheelectronicpropertiesofsemiconductorswiththeprocessingadvantagesandmechanicalpropertiesofpolymers.Themolecularstructuresofseveralpopularconjugatedpolymersareshown in Figure 1.1. Before the revolutionary discovery of conjugated polymers, polymerscienceandtechnologyhadfocusedonsaturatedpolymers,i.e.,conventionallynonconduc-tivepolymers(atermformacromoleculeswithrepeatstructuralunits).Insaturatedpolymers,thevalenceelectronsofthecarbonatomsinthemainchainarehybridizedinsp3configur-ation,andeachcarbonatomisbondedtofourotheratoms.Asaresult,theelectronicorbitalsarefullysaturated.Duetotheirelectronicstructures,saturatedpolymershavewideenergygapsandareelectricallyinsulating.Thefundamentaldifferencebetweenthesaturatedpolymersandtheconjugatedpolymersis the electronic configuration. Figure 1.2 compares the molecular and the electronic struc-turesofsaturated(nonconjugated)polyethyleneandconjugatedpolyacetylene.Inaconju-gatedpolymer,thecarbonorbitalsareinthesp2pzconfiguration,whichleadstooneunpairedelectron(thepelectron)percarbonatom.Aseachcarbonatomiscovalentlybondedtoonlythreeotheratoms,andpzorbitalsofsuccessivecarbonatomsalongthebackboneoverlap,thedelocalizedpbandsarethereforeformed.Asaresult,conjugatedpolymersexhibitsemicon-ductingormetallicproperties,dependingonwhetherthebandsarefilledorpartiallyfilled.Thenumberofpbandsisdeterminedbythenumberofatomswithintherepeatunit.InthecaseofPPV,astherepeatunitcontainseightcarbons,thepbandissplitintoeightsub-bands.Eachsub-bandcanholdonlytwoelectronsperatom,sothefourpsub-bandswiththelowestenergyarefilled,andthefourp*sub-bandswiththehighestenergyareempty.HCCCH(a)sp3 hybridization: tetrahedral symmetryHHHHHCHCHHHCHPolyethyleneHHCCCCCHHHHHPolyacetyleneH2(b)sppz hybridization: hexagonal + π bondFIGURE1.2Electronicandmolecularstructuresof(a)polyethyleneand(b)polyacetylene.The energy difference between the highest occupied p sub-band and the lowest unoccupied p*sub-band defines the p--- p energy gap Eg.One of the advantages of organic semiconductors is that their mechanical and processingproperties can be modified, retaining their electric and optical properties. For example, PPV$2.5 eV. It is insoluble in any organic solvent after conversionis a semiconductor with Egfrom its precursor to a conjugated form [23,58]. However, by attaching alkyl groups to the 2,5positions of its benzyl group, alkyl-PPV derivatives are formed. The alkyl-PPV derivativespossess similar energy band gap and luminescent emission profile as those of PPV, but aresoluble in most nonpolar organic solvents (such as xylene or toluene) and processible inconjugated form [59]. Another advantage of organic semiconductors is that the energy bandgap of a given system can be tuned, retaining its processing capability. For example, byreplacingthealkylgroupsofPPVderivativeswithalkoxygroupsonthe2and5positions(forexample, MEH-PPV, Figure 1.1), the energy band gap can be reduced from 2.5 to 2.1 eV.Figure 1.3 shows the absorption and electroluminescent spectra for a series of PPV deriva-tives.Theenergygapsareintherangeof2.5to1.9eV,providingaspreadof0.6eV.Theseengineeringflexibilitiesareespeciallypromisingforoptoelectricandelectro-opticdeviceapplications.Alongwiththechangeoftheenergybandgap,luminescentprofileandemissioncoloralsochange,asshowninFigure1.3b.Photonicdevicesareoftenclassifiedintothreecategories:lightsources(LEDs,diodelasers,etc.),photodetectors(photoconductors,photodiodes,etc.),andenergyconversiondevices(photovoltaicdevices,solarcells,etc.)[60].Mostofthephotonicphenomenaknowninconventionalinorganicsemiconductorshavebeenobservedinthesesemiconductorpolymers[29,61],includingluminescenceandphotosensitivity.Photoluminescence(PL)de-scribesthephenomenonoflightgenerationunderopticalradiation.Anincomingphotonwithenergylargerthanthebandgapexcitedanelectronfromthefilledpbandtotheunoccupiedp*bandtoformanelectronCholepair(exciton),whichsubsequentlyrecombinestoemitaphoton.Insemiconductorpolymersusedforlightemissionapplications,thephotoluminescentquantumefficiencyistypicallyinthe10C60%range.Photoconductivity包含各类专业文献、高等教育、幼儿教育、小学教育、各类资格考试、应用写作文书、中学教育、文学作品欣赏、DK等内容。　
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