Interface Engineering in Organic Field-Effect Transistors

Preface ix Author Biographies xi List of Acronyms and Abbreviations xiii 1 Introduction 1 1.1 Different Interfaces in OFETs 1 1.2 Brief Historic Overview of Interface Engineering in OFETs 3 1.3 Scope of the Book 3 2 Interfacial Modification Methods 7 2.1 Noncovalent Modification Methods 7 2.1.1 Charge Insertion Layer at the Electrode Surface 7 2.1.2 Dielectric Surface Passivation Methods 9 2.2 Covalent Modification Methods 12 2.2.1 SAM Modification of Electrodes 12 2.2.2 SAM Modification of Dielectrics 12 2.2.2.1 SAM/SiO2 Dielectrics 14 2.2.2.2 SAM/High-k Dielectrics 14 2.2.2.3 Self-Assembled Monolayer Field-Effect Transistors (SAMFETs) 28 2.3 Efforts in Developing New Methods 31 3 Semiconductor/Semiconductor Interface 33 3.1 Influence of Additives on a Material’s Nucleation and Morphology 37 3.1.1 Solvent Additives 37 3.1.2 Nucleating Agents 41 3.1.3 Template-Mediated Crystallization 43 3.1.4 Blending with Insulating Polymers 45 3.1.5 Blending with Polymer Elastomer: Nanoconfinement Effect 50 3.2 Enhancing the Performance Through Semiconductor Heterojunctions 55 3.2.1 Planar Bilayer Heterostructures 57 3.2.2 Molecular-Level Heterojunction 61 3.2.3 Supramolecular Arrangement of the Heterojunctions 64 3.3 Integrating Molecular Functionalities into Electrical Circuits 69 3.3.1 Charge-Trapping-Induced Memory Effect 69 3.3.2 Photochromism-Induced Switching Effect 72 4 Semiconductor/Electrode Interface 77 4.1 Work Function Tuning for Better Contact 79 4.1.1 SAM Modification 80 4.1.2 Charge Insertion Layer Modification 84 4.1.3 Polymer-Based Electrodes 89 4.1.4 Carbon Nanomaterial-Based Electrodes 92 4.1.5 Covalent Bond Formation at the Molecular Level 97 4.2 Installing Switching Effects at Semiconductor/Electrode Interface 100 5 Semiconductor/Dielectric Interface 103 5.1 Dielectric Modification to Tune Semiconductor Morphology 105 5.1.1 Dielectric Surface Energy Control 106 5.1.1.1 Modify with SAM 106 5.1.1.2 Surface Modification with Polymers 112 5.1.2 Dielectric Microstructure Design 113 5.1.2.1 Roughness Effect 114 5.1.2.2 Nano-fabrication Created Microstructure 116 5.1.2.3 Self-assembled Morphology of Dielectric 118 5.2 Eliminating Interfacial Traps 120 5.2.1 Dielectric Surface Passivation (Treatment) Methods 121 5.2.1.1 Polymer Encapsulation of Dielectrics 122 5.2.1.2 Gap Dielectrics 124 5.2.2 SAM/SiO2 Dielectrics 126 5.2.2.1 Provide Efficient Insulating Barrier Height 127 5.2.2.2 Control Surface Polarity and Carrier Density 128 5.2.3 SAM/High-k Dielectrics 131 5.2.3.1 Fundamentals of SAM-Modified High-k Dielectrics 132 5.2.3.2 SAM/High-k Hybrid Dielectrics for Flexible Substrate 134 5.2.4 Self-assembled Monolayer Field-Effect Transistors (SAMFETs) 137 5.2.4.1 Molecule Design for SAMFETs 137 5.2.4.2 Morphology Control of SAMFET 139 5.3 Integrating New Functionalities 141 5.3.1 Photoresponsive Dielectrics 142 5.3.2 Other External Stimuli-Responsive Dielectrics 144 5.3.2.1 Pressure Sensor 145 5.3.2.2 Thermal Sensor 147 5.3.2.3 Magnetic Sensor 147 5.3.2.4 Multifunctional Sensor 148 5.3.3 Integrating Memory Effect at the Dielectrics 148 6 Semiconductor/Environment Interface 155 6.1 Device Optimization to Improve Sensing Performance 156 6.1.1 Monolayer Functionalization 156 6.1.2 Bilayer Heterojunction Approach 158 6.1.3 Remote Floating Gate 159 6.2 OECT-Based and EGOFET-Based Sensors 160 7 Interfacing Organic Electronics with Biology 165 7.1 Integration of OFETs/OECTs with Nonelectrogenic Cells 166 7.2 Integration of Flexible Bioelectronics with Electrogenic Cells 170 7.3 Light/Cell/Device Interfaces 174 8 Concluding Remarks and Outlook 179 8.1 New Challenges in Molecular Design 179 8.2 High-Quality OSC Films: Self-Assembly Control 180 8.3 High-Performance Scalable Flexible Optoelectronics 180 8.4 Exploration of Novel Structures: Organic/2D Heterostructures and Vertical Structures 181 8.5 Instability: Stability in Aqueous Media and Thermal Stability in Hygienic Applications 181 8.6 Multifunctional Sensor Systems 183 References 185 Index 251