Semiconducting Polymers

Transcription

1 Georges Hadziioannou, Paul F. van Hütten (Eds.) Semiconducting Polymers Chemistry, Physics and Engineering WILEY-VCH Weinheim New York Chichester Brisbane Singapore Toronto

2 Contents 1 Poly(arylene vinylene)s - Synthesis and Applications in Semiconductor Devices 1 Michael M. Murray and Andrew B. Holmes 1.1 Introduction Poly(l,4-phenylene vinylene) and its Derivatives The Basic Polymer LED Device Architecture Substituted Poly(phenylene vinylene)s Poly(anthrylenevinylene)s Step-Growth Routes to PPV Derivatives PPV Copolymers Refining the Properties of PPV - Multilayer Devices Multilayer Devices: The Incorporation of Charge-Transporting Layers Electron-Deficient Polymers - Luminescent Transport Layers Other Electron-Deficient PPV Derivatives Electron-Deficient Aromatic Systems Full Color Displays - The Search for Blue Emitters Isolated Chromophores - Towards Blue Emission Comb Polymers with Chromophores on the Side-Chain Chiral PPV - Polarized Emission Poly(thienylene vinylene)s - A Stable Class of Low-Band-Gap Materials Organic Field Effect Transistors (FETs) Synthesis Aldol Route Ring-Substituted PTV Derivatives Vinylene-Substituted PTV Derivatives - Tuning the Gap Conclusions and Outlook 31 Acknowledgements 32 References 32

3 X Contents 2 Oligo- and Poly(phenylene)s 37 Ullrich Scherf and Klaus Müllen 2.1 Introduction Polymers Oxidative Condensation of Benzene Derivatives Transition Metal-Mediated Couplings Other Routes to Poly(p-phenylene)s Oligomers Dendritic and Hyperbranched Poly(phenylene)s Hyperbranched Poly(phenylene) Derivatives Ohgo(phenylene)s Composed of Orthogonally Arranged Arms Dendritic Poly(phenylene)s and Giant Polyaromatic Hydrocarbons (PAHs) Conclusion 60 References 61 3 Disorder and Solitons in Гга/is-Polyacetylene 63 Jasper Knoester and Maxim Mostovoy 3.1 Introduction The Peierls Instability and Solitons Disorder: The Fluctuating Gap Model Disorder-Induced Kinks Concluding Remarks 82 Acknowledgements 83 References 84 4 Gas Phase to Solid State Evolution of the Electronic and Optical Properties of Conjugated Chains: A Theoretical Investigation 87 Jerome Cornil, Donizetti A. dos Santos, David Beljonne, Zhigang Shuai, and Jean-Luc Bredas 4.1 Introduction Theoretical Methodology Wavefunction Analysis of the Excited States in PPV Oligomers Interchain Interactions Absorption Properties of Highly Symmetrical Complexes Photoluminescence Properties of Highly Symmetrical Complexes The Influence of the Number and Relative Orientations of the Interacting Molecules Clusters of Sexithienyl Molecules Conclusions and Outlook 111 Acknowledgements 111 References 112

4 Contents Electronic Structure of Surfaces and Interfaces in Conjugated Polymers 115 Michael Lögdlund and William R. Salaneck 1 Introduction Photoelectron Spectroscopy X-Ray Photoelectron Spectroscopy Ultraviolet Photoelectron Spectroscopy Theoretical Approaches Materials Electronic Structure of /rans-polyacetylene Charge Storage States in Conjugated Polymers Polymer Surfaces and Interfaces Poly(p-phenylenevinylene) Interface Formation Between Aluminum and PPV Interface Formation Between Calcium and PPV Polythiophene Interface Formation Between Aluminum and Polythiophene Interface Formation Between Copper and Polythiophene Polyaniline Polyaniline on Indium Tin-Oxide Summary 144 Acknowledgements 145 References 146 Electronic Structure and Energy Transfer in Solid o-sexithienyl 149 Carlo Taliani, Fabio Biscarini, and Michele Muccini 1 Introduction Experimental Excited Electronic States in Isolated T Single-Crystal Electronic Structure Davydov Splitting Herzberg-Teller Vibronic Coupling Thin Films Growth in High Vacuum 164' 5.2 Thin-Film Morphology Scaling Behavior of Surface Roughness Disorder Effect on Energy Transfer Single-Crystal Fluorescence Thin-Film Fluorescence Morphology-Dependent Polarization of Fluorescence and Electroluminescence Morphology-Dependent Energy Transfer Conclusions 185 Acknowledgements 186 References 187

5 XII Contents 7 Spectroscopy of Photoexcitations in Conjugated Polymers 189 Paul A. Lane, Sergey V. Frolov, and Zev V. Vardeny 7.1 Introduction Experimental Techniques CW Photomodulation Spectroscopy Optically Detected Magnetic Resonance Transient Photomodulation Spectroscopy Non-Linear Optical Spectroscopy Poly(para-phenylene vinylene) Absorption and Photoluminescence Transient Photomodulation Non-Linear Spectroscopy (TPA and EA) CW Photomodulation Polythiophene Linear and Non-Linear Absorption Transient Photomodulation CW Photomodulation Fullerene-Doped DOO-PPV Transient Photomodulation Summary 232 References Photophysics of Methyl-Substituted Poly(para-Phenylene)-Type Ladder Polymers 235 Guiglielmo Lanzani, Sandro De Silvestri, Giulio Cerullo, Salvatore Stagira, Mauro Nisoli, Willi Graupner, Günther Leising, Ulrich Scherf, and Klaus Müllen 8.1 Introduction An Overview of Previous Results Optical Properties Experimental Conventional Pump-Probe Field-Assisted Pump-Probe The Primary Photoexcitations in m-lppp Overview of the Experimental Results A Model for m-lppp Electronic Structure High Excitation Density Scenario The Emission Process in m-lppp Charge Photogeneration in m-lppp Conclusions 256 References 257

6 9 Solid-State Aspects of Conjugated Semiconductors 259 Wilhelm Graupner, Stefan Tasch, and Günther Leising 9.1 Introduction Materials Functionalities in Devices Order in Conjugated Semiconductors Excited-State Spectroscopy Excited States Neutral Photoexcitations Charged Photoexcitations Electroluminescence Devices and Models EL Devices from Conjugated Polymers with a High Defect Concentration EL Devices from Conjugated Polymers with a Low Defect Concentration Electroluminescence from an Electrochemical Cell Carrier Injection and Charge Transport Thermal Emission Field-Induced Injection Charge Recombination and Efficiency Highly Excited Conjugated Films Conclusions 303 Acknowledgements 303 References basing in Conjugated Polymers 309 Uli Lemmer, Andreas Haugeneder, Christian Kallinger, and Jochen Feldmann 10.1 Introduction Stimulated Emission in Organic Materials Gain Narrowing in Conjugated Polymer Thin Films Lasing in Conjugated Polymers Outlook 325 Acknowledgements 320 Appendix I 327 Appendix II 328 References Physics of Polymer Light-Emitting Diodes 333 /. H. Campbell and D. L. Smith 11.1 Introduction Thin Films of Electroluminescent Polymers Electronic Energy Structure Optical Properties Electrical Transport Properties 338

7 XIV Contents 11.3 Device Electronic Structure Internal Photoemission Measurements of Schottky Energy Barriers Built-in Potentials in Device Structures Single-Layer Devices Single-Carrier Structures Two-Carrier Structures Multi-Layer Devices Blocking Layers Transport Layers Two-Carrier Multi-Layer Devices Conclusion 362 References Charge Transport in Random Organic Semiconductors 365 Heinz Bässler 12.1 Introduction Charge Carrier Injection Concepts Comparison with Experiment Space Charge Limited (SCL) Currents The Concept Experimental Results Charge Carrier Transport Concepts Transport in the Presence of Extrinsic Traps Charge Carrier Transport in Conjugated Polymers Time-of-Flight Studies Transient Absorption of Radical Cations Some Remarks Concerning the Nature of Charge-Carrying Moieties 406 Acknowledgements 407 References The Chemistry, Physics and Engineering of Organic Light-Emitting Diodes 411 John Campbell Scott and George G. Malliaras 13.1 Introduction Materials Conjugated Polymers Small Molecules Molecularly Doped Polymers and Polymer Blends Self-Assembled Layers, Langmuir-Blodgett Layers, and Liquid Crystals Electrodes and Interface Modification 421

8 Contents XV Anodes Cathodes Electrode Modification Barrier Layers Transparent Cathodes Device Structures Characterization Device Characteristics Figures-of-Merit Built-in Potential Barrier Heights Charge Transport Photoluminescence Device Physics The Elementary Processes Single-Layer Devices Analytic Theory Numerical Simulations Experimental Studies Multilayer Devices Electrochemical Cells Microcavities Degradation Application of OLEDs in Flat-Panel Displays Display Engineering Units and Conversions Pixels, Patterning, and Drivers Color Encapsulation Outlook 456 Acknowledgements 457 References Physics of Organic Field-Effect Transistors 463 Gilles Horowitz 14.1 Introduction Basic Principles Junctions Metal-Semiconductor (MS) Junction Formation of the Junction The Junction at Equilibrium (Zero Bias) Current-Voltage Characteristic Metal-Insulator-Semiconductor (MIS) Junction Field-Effect Transistors Metal-Insulator-Semiconductor FET (MISFET) Principle of Operation 472

9 XVI Contents Current-Voltage Characteristic Metal-Semiconductor FET (MESFET) Thin-Film Transistor (TFT) Accumulation Mode, Linear Regime Depletion Mode Accumulation Mode, Saturation Regime Mobility Threshold Charge Transport in Organic Materials Localized Versus Delocalized States Hopping Hopping Rate Polarons Polarons in Conjugated Polymers Transport Mechanism of Polarons Multiple Trapping and Release Field-Dependent Mobility Fabrication Techniques Deposition of the Semiconductor Electropolymerization Solution-Processed Deposition Vacuum Evaporation Langmuir-Blodgett All-Organic Devices Materials Oligothiophenes Other Small Molecules Phthalocyanines Pentacene n-type Semiconductors Polymers Models Temperature and Gate Bias Dependence Trap-Limited Transport Polaron and Hopping Models Current-Voltage Characteristics Short-Channel Effects On-Off Current Ratio Concluding Remarks 510 References Conjugated Polymer Based Plastic Solar Cells 515 Christoph J. Brabec and N. Serdar Sariciftci 15.1 Introduction Conjugated Polymers as Photoexcited Donors Optical Properties Linear Optical Properties 518

10 Contents XVII Photoinduced Absorption 521 Quenching of the Intersystem Crossing to the Triplet State 521 Photoinduced IRÄV Studies 522 Time-Resolved Photoinduced Studies Sensitization of Photoconductivity Magnetic Properties Light-Induced Electron Spin Resonance (LESR) Pure Conjugated Polymer Photovoltaic Devices Definitions Basic Transport Properties Metal/Conjugated Polymer Contacts Spectral Response Conjugated Polymer Bilayer Devices Conjugated Polymer/C 60 Heterojunction Photodiodes Conjugated Polymer Bulk Heterojunction Diodes Conjugated Polymer/C 60 Bulk Heterojunction Photodiodes Conjugated Polymer/Conjugated Polymer Bulk Heterojunction Photodiodes Flexible, Large Area, Plastic Solar Cells Stability of Plastic Solar Cells The Guest-Host Approach: Blending with Conventional Polymers Outlook and Strategies 555 Acknowledgements 556 References A Model Oligomer Approach to Semiconducting Polymers 561 Paul van Hütten and Georges Hadziioannou 16.1 Introduction Background The Copolymer Approach to Controlled Light Emission in Polymers Oligomers as Model Compounds for Structure-Property Studies Synthesis and Solution Properties of OPVs Synthesis Introduction General Strategy Synthesis of Model Compounds Three-ring OVPs Synthesis of U-OPV Synthesis of oct-opv5 and Ooct-OPV Synthesis of Cyano-Substituted OPV3s and OPV5s Optical Properties in Solution Comparison of Copolymers and Related Oligomers Three-Ring Chromophores 569

11 XVIII Contents Five-Ring Chromophores Substitution Effects in OPV5s About the Geometry of the Excited State OPVs in the Condensed State Single Crystals Introduction Crystal Structures of Five-Ring OPVs Ooct-OPV Ooct-OPV5-CN' Ooct-OPV5-CN" Crystal Structures of Three-Ring OPVs Ooct-OPV Ome-OPV Ooct-OPV3-CN' Ooct-OPV3-CN" Oct-OPV Oct-OPV3-CN" Optical Properties of Single Crystals Thermal Properties: Liquid-Crystalline Phases Thin Films Introduction Thin-Film Structure Ooct-OPV5 589 Optical Microscopy 589 X-Ray Diffraction (XRD) 589 Atomic Force Microscopy (AFM) Ooct-OPV5-CN' Ooct-OPV5-CN" Ooct-OPV Optical Properties Five-Ring OPVs Ooct-OPV Light Emission Applications of OPVs Introduction Light-Emitting Diodes Single-Layer Devices Influence of Morphology on Device Performance Double-Layer Devices Stimulated Emission Single Crystals Vacuum-Deposited Films Summary and Outlook 608 Acknowledgements 610 References 610 Index 615