Table Of ContentHighlyEfficientOLEDs
Highly Efficient OLEDs
MaterialsBasedonThermallyActivatedDelayedFluorescence
EditedbyHartmutYersin
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Contents
Preface xv
1 TADFMaterialDesign:PhotophysicalBackgroundandCase
StudiesFocusingonCu(I)andAg(I)Complexes 1
HartmutYersin,RafałCzerwieniec,MarselZ.Shafikov,and
AlfiyaF.Suleymanova
1.1 Introduction 1
1.2 TADF,MolecularParameters,andDiversityofMaterials 4
1.2.1 TADFandPhosphorescence 6
1.2.2 MinimizingΔE(S –T ) 7
1 1
1.2.3 Importanceofk (S –S ) 7
r 1 0
1.3 CaseStudy:TADFofaCu(I)ComplexwithLargeΔE(S –T ) 15
1 1
1.3.1 DFTandTD-DFTCalculations 16
1.3.2 FlatteningDistortionsandNonradiativeDecay 16
1.3.3 TADFProperties 18
1.3.4 RadiativeS →S Rate,Absorption,andStrickler–BergRelation 20
1 0
1.4 CaseStudy:TADFofaCu(I)ComplexwithSmallΔE(S –T ) 22
1 1
1.4.1 DFTandTD-DFTCalculations 22
1.4.2 EmissionSpectraandQuantumYields 23
1.4.3 TheTripletStateT andSpin–OrbitCoupling 23
1
1.4.4 TemperatureDependenceoftheEmissionDecayTimeandTADF 28
1.5 EnergySeparationΔE(S –T )andS →S FluorescenceRate 30
1 1 1 0
1.5.1 ExperimentalCorrelationBetweenΔE(S –T )andk (S →S )for
1 1 r 1 0
Cu(I)Compounds 31
1.5.2 QuantumMechanicalConsiderations 32
1.6 DesignStrategiesforHighlyEfficientAg(I)-BasedTADF
Compounds 34
1.6.1 Ag(phen)(P -nCB):AFirstSteptoAchieveTADF 34
2
1.6.2 EmissionQuenchinginAg(phen)(P -nCB) 36
2
1.6.3 StericalHindrance.TuningoftheEmissionQuantumYieldupto
100% 38
1.6.4 DetailedCharacterizationofAg(dbp)(P -nCB) 40
2
1.7 ConclusionandFuturePerspectives 45
Acknowledgments 46
References 46
vi Contents
2 HighlyEmissived10MetalComplexesasTADFEmitterswith
VersatileStructuresandPhotophysicalProperties 61
KoichiNozakiandMunetakaIwamura
2.1 Introduction 61
2.2 PhosphorescenceandTADFMechanisms 62
2.3 Structure-DependentPhotophysicalPropertiesofFour-Coordinate
[Cu(N^N) ]Complexes 64
2
2.4 FlatteningDistortionDynamicsoftheMLCTExcitedState 76
2.5 GreenandBlueEmitters:[Cu(N^N)(P^P)]and[Cu(N^N)(P^X)] 77
2.6 Three-CoordinateCu(I)Complexes 79
2.7 DinuclearCu(I)Complexes 80
2.8 Ag(I),Au(I),Pt(0),andPd(0)Complexes 84
2.9 Summary 85
References 86
3 LuminescentDinuclearCopper(I)ComplexeswithShort
IntramolecularCu–CuDistances 93
AkiraTsuboyama
3.1 Introduction 93
3.2 OverviewofLuminescentDinuclearCopper(I)Complexes 94
3.2.1 Structure 94
3.2.2 LuminescenceProperties 99
3.3 StructuralandPhotophysicalStudiesoftheDinuclearCopper(I)
Complexes:[Cu(μ-C∧N)] (C∧N=2-(bis(trimethylsilyl)methyl)
2
pyridineDerivatives) 100
3.3.1 Outline 100
3.3.2 X-rayCrystallographicStudy 101
3.3.3 PhotophysicalProperties 102
3.3.3.1 AbsorptionSpectrum 102
3.3.3.2 DFTCalculation 103
3.3.3.3 EmissionProperties 104
3.3.3.4 EmissionDecayKineticAnalysis 105
3.3.4 OLEDDevice 110
3.3.5 Experimental 111
3.3.5.1 Synthesis 111
3.3.5.2 Measurement,Calculation,andDevice 111
3.3.5.3 X-rayStructureAnalysis 112
3.3.5.4 DFTCalculation 112
3.3.5.5 OLEDDevice 112
3.4 Conclusion 112
Acknowledgment 113
References 114
Contents vii
4 MolecularDesignandSynthesisofMetalComplexesas
EmittersforTADF-TypeOLEDs 119
MasahisaOsawaandMikioHoshino
4.1 Introduction 119
4.2 Cu(I)ComplexesforOLEDs 122
4.2.1 EnergyLevelsofMolecularOrbitalsinTetrahedralGeometries 122
4.2.2 LigandVariation 123
4.3 MononuclearCu(I)ComplexesforOLEDs 126
4.3.1 Bis(diimine)Type 131
4.3.2 [Cu(NN)(PP)]+ComplexeswithphenorbipyDerivativesas
Ligands 131
4.3.3 [Cu(NN)(PP)]+ComplexeswithNNLigandsOtherThanphenorbipy
Derivatives 134
4.3.4 TetrahedralCu(I)ComplexeswiththeLUMOonthePPLigand 142
4.3.5 Charge-NeutralThree-CoordinateCu(I)Complexes 146
4.4 DinuclearCu(I)ComplexesforOLEDs 155
4.4.1 DinuclearCu(I)ComplexesPossessing{Cu (𝜇-X) }Cores 155
2 2
4.4.2 OtherDinuclearCu(I)Complexes 157
4.5 AnotherGroupofMetalComplexesExhibitingTADF 157
4.6 Conclusion 160
Acknowledgments 160
Appendix 161
4.A.1 SchematicStructuresof1–86 161
4.A.2 AbbreviationsandMolecularStructuresofMaterialsforOLEDs 168
References 171
5 Ionic[Cu(NN)(PP)]+TAD9727FComplexeswithPyridine-based
DiimineChelatingLigandsandTheirUseinOLEDs 177
RongminYuandCan-ZhongLu
5.1 Introduction 177
5.2 TheInfluenceofMolecularandElectronicStructureonEmissive
PropertiesofCu(I)Complexes 178
5.3 HeterolepticDiimine/Diphosphine[Cu(NN)(PP)]+Complexeswith
Pyridine-BasedLigand 181
5.3.1 [Cu(NN)(PP)]+Complexeswith2,2′-bipyridyl-basedLigands 181
5.3.1.1 [Cu(NN)(PP)]+Complexeswith2-(2′-pyridyl)benzimidazoleand
2-(2′-pyridyl)imidazole-basedLigands 182
5.3.2 [Cu(NN)(PP)]+Complexeswith5-(2-pyridyl)tetrazole-based
Ligands 185
5.3.3 [Cu(NN)(PP)]+Complexeswith3-(2′-pyridyl)-1,2,4-triazole-based
Ligands 187
5.3.4 [Cu(NN)(PP)]Complexeswith2-(2-pyridyl)-pyrrolide-based
Ligands 188
viii Contents
5.3.5 [Cu(NN)(PP)]+Complexeswith1-(2-pyridyl)-pyrazole-based
Ligands 189
5.3.6 [Cu(NN)(PP)]+ComplexeswithCarbazolyl-modified
1-(2-pyridyl)-pyrazole-basedLigands 191
5.3.7 [Cu(NN)(PP)]+Complexeswith1-phenyl-3-(2-pyridyl)pyrazole-based
Ligands 192
5.3.8 [Cu(NN)(PP)]+Complexeswith3-phenyl-5-(2-pyridyl)-1H-1,2,4-
triazole-basedLigands 193
5.4 ConclusionandPerspective 194
References 195
6 EfficiencyEnhancementofOrganicLight-EmittingDiodes
ExhibitingDelayedFluorescenceandNonisotropicEmitter
Orientation 199
TobiasD.SchmidtandWolfgangBrütting
6.1 Introduction 199
6.2 OLEDBasics 200
6.2.1 WorkingPrinciple 200
6.2.2 ElectroluminescenceQuantumEfficiency 202
6.2.3 DelayedFluorescence 203
6.2.4 NonisotropicEmitterOrientation 204
6.2.5 OpticalModeling 205
6.3 ComprehensiveEfficiencyAnalysisofOLEDs 206
6.4 CaseStudies 209
6.4.1 TreatingtheOLEDasaBlackBox 209
6.4.2 HighlyEfficientThermallyActivatedDelayedFluorescence
Device 214
6.4.3 LowEfficiencyRoll-OffTriplet–TripletAnnihilationDevice 218
6.5 Conclusion 222
Acknowledgments 223
References 223
7 TADFKineticsandDataAnalysisinPhotoluminescenceandin
Electroluminescence 229
TiagoPalmeiraandMárioN.Berberan-Santos
7.1 TADFKinetics 229
7.1.1 Introduction 229
7.1.2 ExcitationTypes 231
7.1.3 Photoexcitation 232
7.1.3.1 RateEquations 232
7.1.3.2 FluorescenceandPhosphorescenceDecays 232
7.1.3.3 Steady-stateFluorescenceandPhosphorescenceIntensities 233
7.1.3.4 Excited-stateCycles 235
7.1.3.5 TADFOnsetTemperature 238
7.1.3.6 ConditionsforEfficientTADF 239
Contents ix
7.1.4 ElectricalExcitation 240
7.1.4.1 SteadyState 240
7.1.4.2 ConditionsforEfficientElectroluminescence 241
7.1.5 MoreComplexSchemes 244
7.2 TADFDataAnalysis 245
7.2.1 Introduction 245
7.2.2 Steady-stateData 245
7.2.2.1 DelayedFluorescenceandPhosphorescenceIntensitiesasaFunction
ofTemperature:Rosenberg–ParkerMethod 245
7.2.2.2 PromptandDelayedFluorescenceIntensitiesasaFunctionof
Temperature 245
7.2.2.3 DelayedFluorescenceIntensityasaFunctionofTemperature 249
7.2.3 DecayData 249
7.2.4 CombinedSteady-stateandDecayData 250
7.2.4.1 LinearRelationBetweenDelayedFluorescenceLifetimeandIntensity
Ratio 250
7.2.4.2 LinearizedRelationfortheDeterminationofΔE 250
ST
7.3 Conclusion 252
Acknowledgment 252
References 252
8 IntersystemCrossingProcessesinTADFEmitters 257
ChristelM.Marian,JelenaFöller,MartinKleinschmidt,andMihajloEtinski
8.1 Introduction 257
8.1.1 ElectroluminescentEmitters 257
8.1.2 ThermallyActivatedDelayedFluorescence 258
8.2 IntersystemCrossingRateConstants 259
8.2.1 CondonApproximation 260
8.2.1.1 ElectronicSpin–OrbitCouplingMatrixElements 261
8.2.1.2 OverlapofVibrationalWaveFunctions 262
8.2.2 BeyondtheCondonApproximation 263
8.2.3 ComputationofISCandrISCRateConstants 264
8.2.3.1 ClassicalApproach 265
8.2.3.2 StaticalApproaches 265
8.2.3.3 DynamicalApproaches 265
8.3 ExcitationEnergiesandRadiativeRateConstants 266
8.3.1 Time-DependentDensityFunctionalTheory 266
8.3.2 DFT-BasedMultireferenceConfigurationInteraction 267
8.3.3 FluorescenceandPhosphorescenceRates 268
8.4 CaseStudies 269
8.4.1 Copper(I)Complexes 269
8.4.1.1 Three-CoordinatedCu(I)–NHC–PhenanthrolineComplex 270
8.4.1.2 Four-coordinatedCu(I)–bis-PhenanthrolineComplexes 275
8.4.2 Metal-FreeTADFEmitters 277
8.4.2.1 1,2,3,5-Tetrakis(carbazol-9-yl)-4,6-dicyanobenzene(4CzIPN) 279
x Contents
8.4.2.2 MechanismoftheTriplet-to-SingletUpconversionintheAssistant
DopantsACRXTNandACRSA 282
8.5 OutlookandConcludingRemarks 285
References 286
9 TheRoleofVibronicCouplingforIntersystemCrossingand
ReverseIntersystemCrossingRatesinTADFMolecules 297
ThomasJ.PenfoldandJamieGibson
9.1 Introduction 297
9.1.1 BackgroundtoDelayedFluorescence 300
9.1.2 TheMechanismofrISC 302
9.2 BeyondaStaticDescription 303
9.2.1 ObtainingthePotentialEnergySurfaces 304
9.2.1.1 VibronicCouplingModelHamiltonian 306
9.2.2 SolvingfortheMotionoftheNuclei 309
9.2.2.1 MulticonfigurationalTime-DependentHartreeApproach 310
9.2.2.2 DensityMatrixFormalismofMCTDH:𝜌MCTDH 311
9.3 CaseStudies 312
9.3.1 UltrafastDynamicsofaCu(I)–phenanthrolineComplex 313
9.3.2 TheContributionofVibronicCouplingtotherISCof
PTZ-DBTO2 316
9.4 ConclusionsandOutlook 322
References 323
10 Exciplex:ItsNatureandApplicationtoOLEDs 331
Hwang-BeomKim,DongwookKim,andJang-JooKim
10.1 Introduction 331
10.2 FormationandElectronicStructuresofExciplexes 332
10.3 OpticalPropertiesofExciplexes 336
10.3.1 PhotoluminescenceofExciplexes 336
10.3.2 AbsorptionSpectraofExciplexes 338
10.4 DecayProcessesoftheExciplexinSolution 339
10.4.1 FluorescenceRateConstantfortheExciplexState 340
10.4.2 ContactRadicalIonPair(CRIP)VersusSolvent-separatedRadicalIon
Pair(SSRIP) 342
10.4.3 ChargeSeparationVersusChargeRecombination 343
10.4.4 IntersystemCrossing(ISC)intheExciplex 345
10.5 ExciplexesinOrganicSolidFilms 346
10.5.1 PromptVersusDelayedFluorescence 347
10.5.2 SpectralShiftasaFunctionofTime 350
10.6 OLEDsUsingExciplexes 353
10.6.1 ExciplexesasEmitters 353
10.6.2 ExciplexesasSensitizers 356
10.7 SummaryandOutlook 360
Appendix 360
10.A.1 SmallMolecularPairsofDonorsandAcceptorsForming
Exciplexes 360
Contents xi
10.A.2 SmallMoleculeswithElectron-donatingMoietiesForming
Exciplexes 360
10.A.3 SmallMoleculeswithElectron-acceptingMoietiesForming
Exciplexes 365
10.A.4 SmallMoleculeswithElectron-donatingandElectron-accepting
MoietiesFormingExciplexes 368
References 370
11 ThermallyActivatedDelayedFluorescenceMaterialsBasedon
Donor–AcceptorMolecularSystems 377
YeTao,RunfengChen,HuanhuanLi,ChaoZheng,andWeiHuang
11.1 Introduction 377
11.2 TADFOLEDs 380
11.2.1 DeviceStructuresandOperationMechanismsofTADFOLED 380
11.2.2 TADFMoleculesasEmittersforOLEDs 382
11.2.3 TADFMoleculesasHostMaterialsandSensitizersforOLEDs 382
11.2.4 Host-freeTADFOLEDs 383
11.3 BasicConsiderationsinMolecularDesignofTADFMolecules 384
11.3.1 DesignPrinciplesofDonor–AcceptorMolecularSystemsforTADF
Emission 384
11.3.2 ControlofSinglet–TripletEnergySplitting(ΔE ) 386
ST
11.3.3 ModulationofLuminescentEfficiencyofTADFEmission 389
11.4 TypicalDonor–AcceptorMolecularSystemswithHighTADF
Performance 391
11.4.1 Cyano-basedTADFMolecules 391
11.4.2 NitrogenHeterocycle-basedTADFMolecules 396
11.4.3 DiphenylSulfoxide-basedTADFMolecules 405
11.4.4 X-bridgedDiphenylSulfoxide-basedTADFMolecules 407
11.4.5 DiphenylKetone-basedTADFMolecules 408
11.4.6 X-bridgedDiphenylKetoneTADFMolecules 410
11.5 Organoboron-basedTADFMolecules 411
11.6 TADFPolymers 412
11.7 IntermolecularD–ASystemforTADFEmission 413
11.8 SummaryandOutlook 417
References 417
12 PhotophysicsofThermallyActivatedDelayed
Fluorescence 425
AndrewMonkman
12.1 Introduction 425
12.2 CommentsontheTechniquesUsedinOurStudies 428
12.3 BasicAbsorptionandEmissionProperties 428
12.4 PhosphorescenceandTripletStateMeasurements 438
12.5 CharacteristicsoftheDelayedFluorescence 440
12.5.1 Time-resolvedEmissioninSolution 440
12.5.2 Time-resolvedEmissioninSolidState 446
