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1、为了适应公司新战略的发展，保障停车场安保新项目的正常、顺利开展，特制定安保从业人员的业务技能及个人素质的培训计划材料科学与工程学院英语WhiteOrganicLight-EmittingDiodesFirstgradegraduate,opticalengineering,WangNing(P)Abstract:Asimplifiedwhiteorganiclight-emittingdiodes(WOLEDS)employingap-typeinterlayerisdesigned,simultaneouslyrealizinghighefficiency,highcolorrenderin
2、gindex(CRI),lowefficiencyroll-off,lowvoltageandstablecolor.Asflat-panellightsourcestheyareintrinsicallyglare-freeandgeneratelightoveralargearea.Buttheseimprovementsrequirejointresearcheffortsinchemistryandthematerialssciencestodesignbettermaterialsaswellasinphysicsandengineeringtoinventnewdeviceconc
3、eptsanddesignsuitablefabricationschemes.ThisarticlereviewsitscurrentdevelopmentsinthefieldofWOLEDsandputsaspecialfocusonthefuturetrends.Keywords:WhiteOrganicLight-EmittingDiodes;color-renderingindex；externalquantumefficiency.1IntroductionDeviceefficiencyisthesinglemostimportantparameterdescribingthe
4、performanceofanylightsourceandistypicallymeasuredinlumensperwatt(lmW?1),theintegrallightoutputperconsumedelectricalpower.Thismeasurefortheefficiencyisaphotometricunit,meaningthatitisscaledtothesensitivityofthehumaneye.Itshouldthereforemorepreciselybereferredtoasluminousefficacy,althoughthetermeffici
5、encyiswidelyusedtoday.Anotherfrequentlyusedfigure-of-meritistheexternalquantumefficiency(EQE),theaveragenumberofphotonsemittedperunitchargepassedthroughthedevice.Inorderforlighttobeperceivedaswhitebythehumaneye,theemissionspectrumshouldcloselymatchthespectrumemittedbyanincandescentblackbodywithatemp
6、eraturebetween2500and6500K.1Forinstance,sunlighthasacolortemperatureof5800KandthecolortemperatureoflightemittedbyincandescentlightbulbsrangesfromXXto3000K.TheemissioncolorcanalsobedescribedbytheCIE(CommisionInternationaledelclairage)coordinates.TheCIEcoordinatesdescribehowthehumaneyeperceivestheemis
7、sioncolorofanylightsource(withanarbitraryemissionspectrum)usingapairoftwonumbers(x,y).Figure3showstheCIEcoordinatesofseveralreferencespectraandafewexemplaryWOLEDemissionspectrainaso-calledCIEdiagram.AlsoshownaretheCIEcoordinatesofanincandescentblack-bodyoverarangeoftemperatures(Planckianlocus).TheCI
8、EcoordinatesoftheWOLEDswithparticularlyhighluminousefficacytendtobelocatedonthegreenishsideofthePlanckianlocusbecausethehumaneyeperceivesgreenlightasparticularlybright.However,sincetheemissionfromsuchdevicesischaracterizedbyadisturbinggreenhue,carehastobetakenwhencomparingtheefficacyofWOLEDswithsubs
9、tantiallydifferentCIEcoordinates.Figure3AtypicalCIEdiagramthatisusedtocomparetheemissioncolorofdifferentOLEDs.TheoverallefficiencyofanOLEDisinfluencedbyavarietyoffactors.Whenexpressedastheexternalquantumefficiency(EQE),itisgivenbytheproductofthechargerecombinationefficiency(),theratioofgeneratedsing
10、letandtripletexcitedstates(s/t),theinternalelectroluminescencequantumefficiency(q),andthefractionofphotonsextractedfromthestructure(out).Whileitiswidelyassumedthattherecombinationefficiencyapproachesunityintodaysmostefficientdevicestructures,theotherfactorsoftenintroducesignificantloss.Forinstance,t
11、heoutcouplingeffi-ciency,out,inconventionaldevicesisonlyaround20%2,unlessspeciallight-extractionschemesareapplied.3-6Theelectroluminescencequantumefficiencydependsontheactivematerial,butalsoonitslocalsurroundingsandmightthusbewell-belowunity,evenformaterialswithhighphotoluminescencequantumefficiency
12、.7SimilartoconventionalLEDs,WOLEDsaretypicallydrivenbyaconstantDCcurrentandrequirealowbiasvoltage(27V).WhilethismeansthattheyarenotdirectlycompatiblewiththeACpowergrid,therequiredvoltageconversioncanbeintegratedintothehousingofthedeviceatverymoderatecostandismuchlesschallengingthantheup-conversionre
13、quiredforstartingmostgasdischargesources,includingfluorescentlamps.2HistoryDevelopmentThehistoryoforganiclight-emittingdiodes(OLEDs)thatemitwhitelightstartedsome15yearsagowhenKidoandco-workersreportedthattheyhadsucceededinfabricatingOLEDsgeneratinglightthatcontainedwavelengthsacrosstheentirevisiblep
14、artofthespectrum.8Today,researchersthroughouttheworldinbothindustryandacademiaaredevelopingthesewhiteOLEDs(WOLEDs)forthenextgenerationofsolid-statelightsourcesandveryrecentlythefirstproductshavebecomecommerciallyavailable.Besidestheirmanyotherinterestingproperties,WOLEDsareconceptuallydifferentfromm
15、ostlightsourcesthatarecurrentlyonthemarketinthatthelightisgeneratedandemittedoverasizeablearea,rangingfromsub-squarecentimeterinlabsamplestooverseveralsquaredecimetersincurrentprototypesandpotentiallyuptosquare-meterdimensionsinfutureproducts.Therefore,theseorganiclightsourcesareintrinsicallyglare-f
16、reeandcanprovideveryhomogenousillumination,evenintightspaceswherethisisverychallengingtoachieveusingconventional,point-shapedlightsources.ThisfeatureislikelytoallowWOLEDstoenterthelightingmarketasacomplementingtechnologyintheverynearfuture.Initially,theiruniquepropertiesarelikelytofinduseinexclusivemarketswherethequalityofthelightsourcedominatesoverotherfactorssuchasproductioncost.Exampleswherethisiscurrentlyenvisionedinclud
