Costa Light-Emitting Electrochemical Cells

Concepts, Advances and Challenges
1. Auflage 2017
ISBN: 978-3-319-58613-7
Verlag: Springer Nature Switzerland
Format: PDF
Kopierschutz: 1 - PDF Watermark

E-Book, Englisch, 371 Seiten

This book presents the recent achievements towards the next generation of Light-emitting electrochemical cells (LEC). Its first part focus on the definition, history and mechanism of LEC, going then to concepts and challenges and, finally, giving the reader examples of current application of new electroluminescent materials. The chapters are written by different international groups working on LEC.

Dr. Rubén D. Costa holds an independent junior group leader position at the Department of Physical Chemistry I, University of Erlangen-Nuremberg, Germany. His research group focuses on sustainable hybrid lighting technologies based on low-cost and environmentally friendly approaches to fulfill the 'Green Photonics' requirements.

Autoren/Hrsg.

Costa, Rubén D.

Inhaltsverzeichnis

1;Foreword;5
1.1;Light-Emitting Electrochemical Cells: organic semiconductor devices augmented by ions;5
2;Preface;8
3;Contents;10
4;Introduction to the Light-Emitting Electrochemical Cell Technology;12
5;1 Light-Emitting Electrochemical Cells: Mechanisms and Formal Description;13
5.1;Abstract;13
5.2;1.1 Purpose and Aims;14
5.3;1.2 Overview;14
5.3.1;1.2.1 Background;14
5.3.2;1.2.2 Figures of Merit and Device Architectures;17
5.3.3;1.2.3 Suggested Operational Mechanisms for LECs;20
5.3.3.1;1.2.3.1 Electrochemical Doping Model (ECDM);20
5.3.3.2;1.2.3.2 Electrodynamic Model (EDM);20
5.3.3.3;1.2.3.3 Preferential Electrochemical Doping Model (PECDM);21
5.3.4;1.2.4 Current Understanding of Operational Mechanism of LECs;22
5.3.5;1.2.5 Basic Equations to Describe LEC Operation;22
5.3.5.1;1.2.5.1 Drift and Diffusion for Ionic and Electronic Charges;23
5.3.5.2;1.2.5.2 Poisson’s Equation;23
5.3.5.3;1.2.5.3 Binding Energy for Anion/Cation and Ion/Electronic Charge Pairs;23
5.3.5.4;1.2.5.4 Electron–Hole Recombination;24
5.3.5.5;1.2.5.5 Continuity Equations;25
5.3.5.6;1.2.5.6 Boundary Conditions;25
5.4;1.3 Transient Phenomena;26
5.4.1;1.3.1 Turn-on and the Role of Ion Motion;26
5.4.1.1;1.3.1.1 Studies in Planar LECs;27
5.4.1.2;1.3.1.2 Studies in Stacked LECs;31
5.4.2;1.3.2 Polarization Reversal and Hysteresis;32
5.4.3;1.3.3 Degradation, Side Reactions, and Electrochemical Stability;34
5.5;1.4 Steady-State Phenomena;38
5.5.1;1.4.1 Potential and Ion Distribution;38
5.5.1.1;1.4.1.1 EDM;38
5.5.1.2;1.4.1.2 ECDM;39
5.5.1.3;1.4.1.3 PECDM;41
5.5.2;1.4.2 Position and Width of the Recombination Zone;42
5.5.2.1;1.4.2.1 Studies in Planar LECs;42
5.5.2.2;1.4.2.2 Electrical Impedance Spectroscopy;43
5.5.2.3;1.4.2.3 Studies in Stacked LECs;43
5.5.3;1.4.3 Current-Voltage Characteristic;45
5.5.4;1.4.4 Luminescence Quenching and Reabsorption;47
5.5.5;1.4.5 Color Tuning and Cavity Effects;49
5.5.6;1.4.6 Efficiency: Values and Limits;50
5.6;1.5 Conclusion and Outlook;51
5.7;References;51
6;Definition and Role of the Ionic Additives;56
7;2 Optical-Beam-Induced-Current Imaging of Planar Polymer Light-Emitting Electrochemical Cells;57
7.1;Abstract;57
7.2;2.1 Polymer Light-Emitting Electrochemical Cells;57
7.2.1;2.1.1 Background;57
7.2.2;2.1.2 Frozen-Junction LECs;59
7.2.3;2.1.3 Extremely Large Planar LECs;62
7.3;2.2 Scanning Optical Imaging of Planar LECs;65
7.3.1;2.2.1 The Optical-Beam-Induced Current (OBIC) Technique;65
7.3.2;2.2.2 OBIC Scanning of Planar LECs with a Micromanipulated Cryogenic Probe Station;69
7.3.3;2.2.3 Concerted OBIC and Scanning PL Imaging of Planar LECs with a Fluorescence Microscope;70
7.4;2.3 OBIC and Scanning PL Probing of a Frozen Planar p-i-n Junction;72
7.4.1;2.3.1 Introduction;72
7.4.2;2.3.2 Experimental Details;72
7.4.3;2.3.3 Resolving the Depletion Width of a Planar p-i-n Junction;73
7.5;2.4 High-Resolution OBIC and Scanning PL Imaging of a Frozen Planar Polymer p-n Junction;75
7.5.1;2.4.1 Introduction;75
7.5.2;2.4.2 Experimental Details;75
7.5.3;2.4.3 Results and Discussion;76
7.6;2.5 Conclusion and Outlook;80
7.7;Acknowledgements;80
7.8;References;81
8;3 Optical Engineering of Light-Emitting Electrochemical Cells Including Microcavity Effect and Outcoupling Extraction Technologies;84
8.1;Abstract;84
8.2;3.1 Introduction;85
8.2.1;3.1.1 Microcavity Effect in Organic Thin-Film Devices;85
8.2.2;3.1.2 Optical Modes in Organic Thin-Film Devices;85
8.2.3;3.1.3 Organization of This Chapter;86
8.3;3.2 Tailoring Output EL Spectrum of LECs by Employing Microcavity Effect;86
8.3.1;3.2.1 Suppression of Blue-Green Emission to Achieve Purer White EL;86
8.3.2;3.2.2 Non-doped White LECs Based on a Single Emissive Material;88
8.3.3;3.2.3 Non-doped Near-Infrared LECs Based on Interferometric Spectral Tailoring;90
8.4;3.3 Outcoupling Extraction Technologies to Enhance Device Efficiencies of LECs;92
8.4.1;3.3.1 Enhancing Light Extraction by Employing Microlens Array;92
8.4.2;3.3.2 Recycling the Trapped EL by Employing Red Color Conversion Layers;93
8.4.3;3.3.3 Recycling the Trapped EL by Employing Waveguide Coupling;95
8.5;3.4 Conclusion and Outlook;97
8.6;Acknowledgements;98
8.7;References;98
9;4 The Use of Additives in Ionic Transition Metal Complex Light-Emitting Electrochemical Cells;100
9.1;Abstract;100
9.2;4.1 Polymer Additives to Decrease Self-quenching for Improved Efficiency;100
9.2.1;4.1.1 Layer-by-Layer Techniques;101
9.2.2;4.1.2 Blended Inert Polymers;102
9.3;4.2 Host/Guest LECs to Control Color and Improve Efficiency;104
9.4;4.3 Ionic Additives for Improved Ion Redistribution and LEC Performance;108
9.4.1;4.3.1 Electric Double Layer Formation and Charge Injection;108
9.4.2;4.3.2 Electrolyte—Salt Combinations;108
9.4.3;4.3.3 Ionic Liquids;109
9.4.3.1;4.3.3.1 Ionic Liquids Shown to Decrease Turn-on Time;109
9.4.3.2;4.3.3.2 High Ionic Conductivity Ionic Liquids Yield High Peak Luminance;110
9.4.3.3;4.3.3.3 Ionic Liquids in LECs Under AC and Pulsed Operation;112
9.4.4;4.3.4 Lithium Salt Additives;112
9.4.4.1;4.3.4.1 Lithium Additives Improve ITMC-Based LECs;114
9.4.4.2;4.3.4.2 Scanning Probe Study of Lithium Salt Additives;117
9.4.4.3;4.3.4.3 Optimal Lithium Salt Concentration;119
9.4.4.4;4.3.4.4 Electrochemical Impedance Spectroscopy of LECs with Lithium Salt Additive;121
9.4.4.5;4.3.4.5 Counterion Dependence of Lithium Salts;123
9.5;4.4 Outlook;123
9.6;Acknowledgements;124
9.7;References;124
10;5 Improving Charge Carrier Balance by Incorporating Additives in the Active Layer;127
10.1;Abstract;127
10.2;5.1 Introduction;127
10.2.1;5.1.1 Characteristics of Light-Emitting Electrochemical Cells (LECs);127
10.2.2;5.1.2 Charge Carrier Balance in LECs;130
10.2.3;5.1.3 Organization of this Chapter;131
10.3;5.2 Optical Technique to Probe Charge Carrier Balance in LECs;131
10.4;5.3 Incorporating Carrier Trappers in LECs;133
10.5;5.4 Incorporating Salts in LECs;137
10.6;5.5 Incorporating Carrier Transport Materials in LECs;139
10.7;5.6 Conclusion and Outlook;141
10.8;Acknowledgements;142
10.9;References;142
11;6 Morphology Engineering and Industrial Relevant Device Processing of Light-Emitting Electrochemical Cells;144
11.1;Abstract;144
11.2;6.1 Introduction;144
11.3;6.2 Film Morphology and Polymer Solid Electrolytes;147
11.3.1;6.2.1 Introduction;147
11.3.2;6.2.2 LEC Active Layer Morphology: PSE Phase Separation;148
11.3.3;6.2.3 Effect of the PSE Molecular Weight on the Film Morphology;148
11.3.4;6.2.4 Effect of the PSE Monomer Ratio on the Film Morphology;153
11.4;6.3 LEC Fabrication by Scalable Methods;156
11.4.1;6.3.1 Introduction;156
11.4.2;6.3.2 Gravure Printing;157
11.4.2.1;6.3.2.1 Gravure-Printed Polymer-Based LECs;158
11.4.2.2;6.3.2.2 Gravure-Printed Small Molecule-Based LECs;160
11.4.3;6.3.3 Inkjet Printing;161
11.4.4;6.3.4 Slot-Die Coating;161
11.4.5;6.3.5 Spray Coating;164
11.5;6.4 Conclusion;166
11.6;Acknowledgements;166
11.7;References;166
12;Traditional and New Electroluminescent Materials;169
13;7 Development of Cyclometallated Iridium(III) Complexes for Light-Emitting Electrochemical Cells;170
13.1;Abstract;170
13.2;7.1 Introduction;170
13.3;7.2 Synthetic Approaches to [Ir(C^N)2(N^N)]+ Complexes;173
13.3.1;7.2.1 Use of [Ir2(C^N)4(?-Cl)2] Dimers;173
13.3.2;7.2.2 Solvento Complexes;175
13.4;7.3 Development of Ligand Types in [Ir(C^N)2(N^N)]+ Emitters;176
13.4.1;7.3.1 Archetype [Ir(ppy)2(bpy)]+ and [Ir(ppy)2(phen)]+ Complexes;176
13.4.2;7.3.2 Functionalizing N^N Ligands in [Ir(ppy)2(bpy)]+ and [Ir(ppy)2(phen)]+ with Bulky Substituents;178
13.4.3;7.3.3 Cyclometallating Ligands with Nitrogen-Rich Heterocycles;180
13.4.4;7.3.4 N^N Ligands with Nitrogen-Rich Heterocycles;182
13.4.5;7.3.5 Designing N^N Ligands for Red-Emitting Iridium(III) Complexes;184
13.5;7.4 Increasing Stability Through Intramolecular ?-Stacking in [Ir(C^N)2(N^N)]+ Luminophores;187
13.6;7.5 Effects on LEC Stability of Introducing Fluoro-Substituents into Cyclometallating Ligands;192
13.7;7.6 Fluorine-Free, Blue-Shifted Emitters;195
13.8;7.7 Replacing the N^N Ligand in [Ir(C^N)2(N^N)]+ Emitters by N-Heterocyclic Carbenes;196
13.9;7.8 Effects of Incorporating Peripheral, Charged Domains in Ir-iTMCs and the Design of Anionic Ir-iTMCs;199
13.10;7.9 Conclusions;202
13.11;Acknowledgements;202
13.12;References;202
14;8 Recent Advances on Blue-Emitting Iridium(III) Complexes for Light-Emitting Electrochemical Cells;206
14.1;Abstract;206
14.2;8.1 Introduction;207
14.3;8.2 Blue-Emitting Iridium(III) Complexes for LECs;207
14.3.1;8.2.1 Modification on [Ir(ppy)2(bpy)]+;208
14.3.2;8.2.2 Using Ancillary Ligands Beyond the bpy Skeleton;212
14.3.3;8.2.3 Using Ancillary Ligands with Strong Ligand Field Strength;218
14.3.4;8.2.4 Using Cyclometalating Ligands Beyond the ppy Skeleton;222
14.4;8.3 Conclusion and Outlook;228
14.4.1;8.3.1 Current Status;228
14.4.2;8.3.2 Challenges and the Future;235
14.5;Acknowledgements;236
14.6;References;236
15;9 Thermally Activated Delayed Fluorescence Emitters in Light-Emitting Electrochemical Cells;239
15.1;Abstract;239
15.2;9.1 Introduction;239
15.3;9.2 Photoluminescence Mechanism: Fluorescence, Phosphorescence, and TADF;241
15.4;9.3 SM-Based LECs;242
15.4.1;9.3.1 State-of-the-Art of Blue-Emitting SM-Based LEC without TADF Mechanism;242
15.4.2;9.3.2 SM-Based LEC with TADF Mechanism;250
15.4.2.1;9.3.2.1 Designing TADF SMs;250
15.4.2.1.1;Application of TADF in Working Devices;250
15.4.2.2;9.3.2.2 Critical Outlook;254
15.5;9.4 Copper(I) Complexes Based LECs with TADF Mechanism;256
15.5.1;9.4.1 Designing TADF Copper(I) Complexes;256
15.5.1.1;9.4.1.1 LEC Performance;256
15.5.2;9.4.2 Critical Outlook;265
15.6;9.5 Conclusions;266
15.7;Acknowledgements;266
15.8;References;266
16;10 White Emission from Exciplex-Based Polymer Light-Emitting Electrochemical Cells;269
16.1;Abstract;269
16.2;10.1 Introduction;270
16.2.1;10.1.1 Energy, Electricity, and Lighting;270
16.2.2;10.1.2 Polymer White Light-Emitting Electrochemical Cells;271
16.2.2.1;10.1.2.1 Definition;271
16.2.2.2;10.1.2.2 Strategies for Obtaining White Emission from Polymer-Based Light-Emitting Electrochemical Cells;272
16.3;10.2 White Light-Emitting Electrochemical Cells Based on Exciplex Emission;275
16.3.1;10.2.1 Basic Concepts and Strategies;275
16.3.2;10.2.2 Optical Properties of Exciplexes Formed Between PFD and Amine Molecules;277
16.3.3;10.2.3 Characteristics of White-Emitting PLECs Based on Exciplex Emission;281
16.3.4;10.2.4 Strategy for Realizing Highly Efficient Exciplex-Based White-Emitting PLECs;282
16.4;10.3 Exciplex-Based LECs Made with Small-Molecule Compounds;284
16.5;10.4 Perspectives and Future Opportunities;286
16.6;References;287
17;11 Luminescent Cationic Copper(I) Complexes: Synthesis, Photophysical Properties and Application in Light-Emitting Electrochemical Cells;289
17.1;Abstract;289
17.2;11.1 Introduction;290
17.3;11.2 Complexes of General Formula [Cu(N^N)2][X];291
17.4;11.3 Complexes of General Formula [Cu(P^P)(N^N)][X];294
17.4.1;11.3.1 [Cu(P^P)(N^N)][X] Complexes Coordinated to 1,10-Phenanthroline;294
17.4.2;11.3.2 [Cu(P^P)(N^N)][X] Complexes Coordinated to 2,2-Bypiridine;298
17.4.3;11.3.3 [Cu(P^P)(N^N)][X] Complexes Coordinated to 2-Pyridyl-Aza-Heterocycles;304
17.4.4;11.3.4 LEC Devices Prepared with [Cu(P^P)(N^N)][X] Complexes;307
17.5;11.4 Complexes of General Formula [Cu(P^P)2][X];311
17.6;11.5 Cationic Copper(I) Complexes Coordinated to Tripodal P^P^P or N^N^N Ligand;313
17.7;11.6 Polynuclear Cationic Copper(I) Complexes Based on Diphosphine and Dinitrogen Ligands;314
17.8;11.7 Cationic Copper(I) Complexes Coordinated to P^N Ligand;319
17.9;11.8 Cationic Copper(I) Complexes Coordinated to N-Heterocyclic Carbene Ligand;320
17.10;11.9 Conclusions;325
17.11;Acknowledgements;326
17.12;References;326
18;12 Small Molecule-Based Light-Emitting Electrochemical Cells;330
18.1;Abstract;330
18.2;12.1 Introduction;330
18.3;12.2 General Consideration of SM-LECs: Device Fabrication and Device Architecture;331
18.4;12.3 LEC Materials;332
18.4.1;12.3.1 Neutral SM-Based LECs;333
18.4.2;12.3.2 Ionic SM-Based LECs;337
18.4.3;12.3.3 Dyad-Endorsed LECs;342
18.4.4;12.3.4 Organic–Inorganic Host–Guest Systems Involving SMs in LECs;343
18.5;12.4 Conclusions and Outlook;347
18.6;Acknowledgements;348
18.7;References;348
19;13 Quantum Dot Based Light-Emitting Electrochemical Cells;351
19.1;Abstract;351
19.2;13.1 Introduction to Semiconductor Nanocrystals;352
19.3;13.2 Colloidal QDs;353
19.3.1;13.2.1 Type-I Core-Shell NCs;354
19.3.1.1;13.2.1.1 CdSe-Based QDs—QDs Used in LECs;355
19.4;13.3 Perovskites;355
19.4.1;13.3.1 Perovskite Nanostructures;357
19.4.2;13.3.2 Synthesis of Perovskite NCs;360
19.5;13.4 Applications of NCs into LECs;363
19.5.1;13.4.1 Core-Shell QDs Emitters for LECs;363
19.5.2;13.4.2 Perovskite Emitters for LECs;366
19.6;13.5 Conclusions and Outlook;369
19.7;Acknowledgements;369
19.8;References;369