Organic Light-Emitting Transistors Towards the Next Generation Display Technology

Provides an overview of the developments and applications of Organic Light Emitting Transistors (OLETs) science and technology

This book discusses the scientific fundamentals and key technological features of Organic Light Emitting Transistors (OLETs) by putting them in the context of organic electronics and photonics. The characteristics of OLETs are benchmarked to those of OLEDs for applications in Flat Panel Displays and sensing technology. The authors provide a comparative analysis between OLED and OLET devices in order to highlight the fundamental differences in terms of device architecture and working principles, and to point out the enabling nature of OLETs for truly flexible displays. The book then explores the principles of OLET devices, their basic optoelectronic characteristics, the properties of currently available materials, processing and fabrication techniques, and the different approaches adopted to structure the active channel and to control organic and hybrid interfaces.

• Examines the photonic properties of OLETs, focusing on the external quantum efficiency, the brightness, the light outcoupling, and emission directionality
• Analyzes the charge transport and photophysical properties of OLET, emphasizing the excitonic properties and spatial emitting characteristics
• Reviews the key building blocks of the OLET devices and their role in determining the device’s performance
• Discusses the challenges in OLET design, namely color gamut, power efficiency, and reliability
• Presents key applications of OLET devices and their potential impact on display technology and sensing

Michele Muccini is Director of CNR-ISMN and President of the public-private Industrial Consortium MIST E-R. He is co-founder of E.T.C. S.r.l., a start-up company of the SAES Group focussed on the development of organic light emitting technologies. Muccini is inventor of the OLET, the organic electroluminescent transistor and of the OCST, an organic sensor for the stimulation and recording of neural networks. He is author of about 160 scientific publications in international journals and inventor of 20 international patents related to OLET technology.

Stefano Toffanin is a permanent researcher and leader of a group of 10 people focused on the development of flexible organic photonics and electronics at CNR-ISMN in Bologna. His main research interest is the spectroscopic investigation of light-emitting and charge-transport organic systems for use in organic nanostructured opto-electronic devices by means of non-conventional ultrafast optical probes. His current focus is on organic multifunctional flexible platforms for smart applications in nanophotonics and biodiagnostics. He is author of more than 40 papers and 4 international patents.

1 Introduction 1

2 Organic Light‐Emitting Diodes 5

2.1 Oled Device Structure and Working Principles 5

2.2 Applications of Oled Technology 20

2.3 Diode Versus Transistor Architecture for Light Emission 31

2.4 Conclusions 38

References 38

3 Organic Light‐Emitting Transistors: Concept, Structure, and Optoelectronic Characteristics 45

3.1 Working Principles of Olets 46

3.2 Device Structures 57

3.3 Thin‐Film Olets 61

3.3.1 Single‐Layer Olets 61

3.3.2 Multilayer Olets 68

3.4 Single‐Crystal Olet 73

3.5 Conclusions 82

References 82

4 Key Building Blocks of Olets 87

4.1 Dielectric Layer 87

4.2 Emissive Ambipolar Semiconductors 103

4.3 Charge‐Injecting Electrodes 129

4.4 Conclusions 146

References 146

5 Charge‐Transport and Photophysical Processes in Olets 153

5.1 Charge Transport in Olets 153

5.2 Fundamental Excitonic Processes and Modeling of Olets 170

5.3 Excitonic Recombination and Emitting Area in Olets 180

5.4 Conclusions 195

References 196

6 Photonic Properties of Olets 201

6.1 External Quantum Efficiency 201

6.2 Brightness 212

6.3 Light Outcoupling and Emission Directionality 220

6.4 A Possible Route for Organic Injection Lasing 230

6.5 Conclusions 236

References 236

7 Applications Of Organic Light‐Emitting Transistors 243

7.1 Olet Display Technology 244

7.2 Olet‐Based Sensing 254

7.3 Open Issues and Next Development Targets 265

7.3.1 Color Gamut 265

7.3.2 Power Efficiency 267

7.3.3 Lifetime 268

7.4 Conclusions 271

References 271

8 Conclusions 277

Index 279

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