OLED设计-FDTD软件

HowtoSimulateandOptimizeOLED/LEDDevicesLumericalSolutions,Inc.OutlineIntroductionMotivationChallengesSimulationmethodologyExampleSimulationtipsQuestionsandAnswersIntroductionWesimulatelightinteractingwithwavelengthscalestructuresMODESolutionsFDTDSolutions12mm20mm6mmIntroductionPlanarlightemittingdiodes(LEDs)andorganicLEDs(OLEDs)donothaveoptimalquantumefficiencybecausemuchofthelightgeneratedinsidethedeviceremainstrappedbytotalinternalreflection(TIR)untilitiseventuallyabsorbed.MicroandnanoscalepatterningcancontributetoincreasingthequantumefficiencyofthesedevicesOneofthekeychallengesiscalculatingtheeffectsofthesepatternsSimulationgivestheopportunitytocheaplyandquicklytestideas,optimizedesignsandsolveproblemsExpensiveandtime-consumingtobuildprototypesDesignoptimizationischallengingandresultsarenotalwaysintuitiveWhysimulateOLEDs/LEDsIntroductionComplicatedsimulationmethodologyComplexdevicegeometrywithmanysmallwavelength-scalefeaturesBroadbandMaterialdispersionSourcemodelingManyeffects•Internalquantumefficiency,lightextraction,electricalLargesimulations,longsimulationtimesTediouspostprocessingSimulationChallengesIsimulate15x15x3um^3LED…PriortoFDTDSolutions,thiswasnotpossible.”H.GREINERH.GREINERPHILIPSPHILIPSIntroductionFiniteDifferenceTimeDomain(FDTD)isastate-of-the-artmethodforsolvingMaxwell’sequationsincomplexgeometriesFewinherentapproximations=accurateAverygeneraltechniquethatcandealwithmanytypesofproblemsArbitrarilycomplexgeometriesOnesimulationgivesbroadbandresultsCanbeusedtostudytheeffectsofmicroandnanoscalepatterninganditsimpactontheefficiencyoftheOLED/LEDdeviceFDTDIntroductionThereare2methodsforincreasingtheoverallefficiencyofLEDs/OLEDsusingpatterning:LightExtractionEfficiency(LEE):IncreasingthepercentageofgeneratedphotonsthatwilleventuallymakeitintothedesiredregioninairInternalQuantumEfficiency(IQE):Increasingthenumberofgeneratedphotons(increasingtheradiativedecayrate)TotalQuantumEfficiency(QE)=IQE*LEEWhatdowewanttodosimulate?IncreasingtheefficiencyFractionofemittedpowerthatcanescapeintoair(orintoadesiredsolidangle)IncreasingthelightextractionefficiencyH.GreinerandJ.PondSimulationofLightExtractionfromOLEDSusingFDTDSolutionsIncreasingtheefficiencyFDTDSolutionscanmodeltheeffectofmicroscopicpatterningCalculatefractionofemittedpowerthatcanescapeanyregioninglassorairIncreasingthelightextractionefficiencynopatterningpatterning://(IQE)Increasingtheinternalquantumefficiency(IQE)IncreasethenumberofgeneratedphotonsRadiativedecayprocessescancompetemoreefficientlywithnon-radiativeprocessesCancalculatethisinFDTDSolutionsbyrelatingthedecayratetothepowerradiatedbyadipolesourceOthereffectsSimulationMethodologySimulationmethodologyDesignparameterizationMaterialpropertiesSimulationregionBoundaryconditions,simulationspanSourcemodelingResultanalysisInternalQuantumEfficiencyExtractionEfficiencyDesignparameterizationParameterizetheOLEDdesignCreatepropertiesappropriateforyourdeviceUsethescriptedparameterizationParameterizationcanincludepositionofsourcesandmonitorsAnygroupcansetpropertiesofthechildrenDesignparameterizationEssentialforReproducibilityEasyparametersweepsOptimizationLumerical’shierarchicalgrouplayoutandscriptbasedparameterizationmakesalmostanythingpossibleItisworththeinitialinvestment!DesignparameterizationMaterialproperties–broadbandsimulationsFiniteDifferenceTimedomain(FDTD)simulationgivesbroadbandresultLED/OLEDdevicesutilizemanydispersivematerialsWell-knownfrequencydomainrelationshipUserscandefinetheirownmodel,orimportfromexperimentaldata(realandimaginaryɛ(ω))FDTDisatimedomaintechnique:relationship?)()()(EDttdtttEtEttD0)()()()()(Materialproperties–broadbandsimulationsCommonsolutionsareLorentzorDrudemodelsOfteninsufficientforrealmaterialsLumerical’sMulti-CoefficientModel(MCM)cansolveformaterialswitharbitrarydispersionsuchasGaAs,Alq3,Al,ITO…etcGaAsAlq3AlITOSourcesLightisgeneratedintheactivelayerofanOLED/LEDastheinjectedcurrentofelectronsandholesrecombinetocreatephotons(spontaneousemission).Eachphotonhasarandomdirection,phaseandpolarization.Inpractice,itispossibletotreatthegeneratedlightclassicallyusingelectromagneticpointdipolesources.Apointdipolesourceissimplyanoscillatingdipolefieldthathasaspecificorientation,phaseandpolarization.Sources-CoherenceFDTDisafundamentallycoherentsimulationmethodTemporalincoherenceThephase,j,ofthelightshiftsrandomlyovertime,onatimescaletcItisnotpracticaltosimulatethestatisticsoftemporalincoherencebecausetcT.ssTttEtEc1115010102))(cos()(tjSources-CoherenceSpatialincoherencecanbesimulatedusingtheergodicprincipleEachensembleconsistsofdipoleswithrandomizedphase,amplitude,position,orientationandpulsetimeAlargenumberofensemblesmustbeaveragedThereisastatisticalerrorassociatedthatdec