Handbook of Organic Materials for Optical and (Opto)Electronic Devices

Properties and Applications

Oksana Ostroverkhova

• Publisher: Woodhead Publishing
• Year: 2013
• eBook ISBN: 9780857098764
• Topic: Technology & Engineering
• Subtopic: Physical & Theoretical Chemistry
• Index: Technology & Engineering

Small molecules and conjugated polymers, the two main types of organic materials used for optoelectronic and photonic devices, can be used in a number of applications including organic light-emitting diodes, photovoltaic devices, photorefractive devices and waveguides. Organic materials are attractive due to their low cost, the possibility of their deposition from solution onto large-area substrates, and the ability to tailor their properties. The Handbook of organic materials for optical and (opto)electronic devices provides an overview of the properties of organic optoelectronic and nonlinear optical materials, and explains how these materials can be used across a range of applications.Parts one and two explore the materials used for organic optoelectronics and nonlinear optics, their properties, and methods of their characterization illustrated by physical studies. Part three moves on to discuss the applications of optoelectronic and nonlinear optical organic materials in devices and includes chapters on organic solar cells, electronic memory devices, and electronic chemical sensors, electro-optic devices.The Handbook of organic materials for optical and (opto)electronic devices is a technical resource for physicists, chemists, electrical engineers and materials scientists involved in research and development of organic semiconductor and nonlinear optical materials and devices.- Comprehensively examines the properties of organic optoelectronic and nonlinear optical materials- Discusses their applications in different devices including solar cells, LEDs and electronic memory devices- An essential technical resource for physicists, chemists, electrical engineers and materials scientists

1

Small molecular weight materials for (opto)electronic applications: overview

Y. Shirota, Fukui University of Technology, Japan

H. Kageyama, University of the Ryukyus, Japan

Abstract:

This chapter gives an overview of organic materials, focusing on molecular materials for use in optoelectronic devices such as organic photoreceptors, organic photovoltaic devices (OPVs), and organic light-emitting diodes (OLEDs). A description of the historical development of organic optoelectronics is provided. This is followed by a review of the principles and operation processes involved in such optoelectronic devices and the molecular materials for use in such devices. Finally, device structures and performance are discussed.

Key words

organic optoelectronics

organic light-emitting diode (OLED)

organic photovoltaic device (OPV)

organic semiconductor

molecular material

1.1 Introduction

Electronic, optoelectronic, and photonic devices using inorganic semiconductors, e.g., silicon transistor-based computers, light-emitting diodes (LEDs), devices based on semiconductor lasers, and optical communication devices such as waveguides, have greatly contributed to the arrival of the present information-oriented society. In recent years, new fields of organic electronics, organic optoelectronics, and organic photonics using organic materials have opened up. These newly emerging fields of science and technology are mainly concerned with novel thin-film, flexible devices using organic materials. Devices using organic materials have the following advantages over inorganic semiconductor-based devices; lightweight, flexibility, and potentially low cost. Organic photovoltaic devices (OPVs), organic light-emitting diodes (OLEDs), and organic field-effect transistors (OFETs) have been the central subjects of current research and development in the fields of organic electronics and optoelectronics.

Electrophotography has long been applied to practical copying machines and printers, making significant contributions to the development of information-oriented society. OPVs have been receiving a great deal of attention as promising candidates for next-generation solar cells that contribute to solving the present global issues of the environment and energy. OLEDs have already found successful practical application as portable, flat-panel displays for various purposes and have been expected to be a candidate for next-generation solid-state lighting. OFETs are expected to be key devices for driving various devices in the printed electronics, which aim to fabricate the whole part of thin-film, flexible organic devices by use of printing techniques.

Organic electronics, optoelectronics, and photonics constitute interdisciplinary fields that cover physics, chemistry, biology, and materials science. That is, the science and technology of these fields, which can be termed organic functional materials science or organic device science, include wide areas from the molecular design and synthesis of photo and electroactive organic materials to the elucidation of their physical and chemical properties as well as their structures, fabrication of devices using synthesized organic materials, evaluation of their performance, and creation of new knowledge underlying the operation of organic devices. As photo and elec-troactive organic materials, including both small molecules and polymers, are expected to be key materials for organic electronics, optoelectronics, and photonics, and for 21st-century industries related to information and energy, the creation of new photo and electroactive organic materials is a challenging subject.

This chapter deals with an overview of organic materials, focusing on molecular materials for use in optoelectronic devices such as organic pho-toreceptors in electrophotography, OPVs, and OLEDs. Following the historical development in organic optoelectronics, principles of and operation processes involved in optoelectronic devices, molecular materials for use in such devices, and device structures and performance are discussed. Book and review articles on optoelectronic devices such as electrophotography, OPVs, and OLEDs are available (Mort and Pai, 1976; Borsenberger and Weiss, 1993; Miyata and Nalwa, 1997; Thelakkat, 2002; Forrest, 2004; Sun and Sariciftci, 2005; Kafafi, 2005; Müllen and Scherf, 2006; Shirota and Kageyama, 2007; Roncali et al., 2007; Mishra et al., 2009).

1.2 Historical development in organic (opto)electronics: devices and materials

It was in the 1960s that electrophotographic copying machines using amorphous selenium as a photoreceptor material were put into practical use. In the early 1970s, an organic photoreceptor using a single layer of a poly(VV-vinylcarbazole) (PVCz) / 2,4,7-trinitrofluorenone (TNF) charge-transfer complex was developed (Schaffert, 1971) and used. This can be regarded as the beginning of organic optoelectronics. Photoreceptors with two-layer structures consisting of a charge-carrier generation layer (CGL) and a charge-carrier transport layer (CTL) have soon become the main focus in the development of photoreceptors (Regensburger, 1968; Mort, 1972; Mort and Nielsen, 1972; Melz et al., 1977). The electrophotographic process has later expanded its application to printers for a computer terminal. A number of organic materials have been developed for use in the CGL and CTL in photoreceptors.

Related to applications of organic photoconductors for use in photore-ceptors in electrophotography, photoconductivity of organic materials has been extensively studied (Mort and Pai, 1976; Borsenberger and Weiss, 1993). The electric-field dependence of the photogeneration of charge carriers has been analyzed in terms of the Onsager theory (Onsager, 1938) for anthracene single crystals (Batt et al., 1968; Chance and Braun, 1976; Lyons and Milne, 1976), PVCz (Hughes, 1971; Pfister and Williams, 1974), PVCz/ TNF system (Melz, 1972), phthal...

Table of contents

• Cover image
• Title page
• Table of Contents
• Copyright
• Contributor contact details
• Woodhead Publishing Series in Electronic and Optical Materials
• Preface
• Chapter 1: Small molecular weight materials for (opto)electronic applications: overview
• Chapter 2: Influence of film morphology on optical and electronic properties of organic materials
• Chapter 3: Doping effects on charge transport in organic materials
• Chapter 4: Third-order nonlinear optical properties of π-conjugated polymers with thiophene units and molecular assembly of the polymers
• Chapter 5: Small molecule supramolecular assemblies for thirdorder nonlinear optics
• Chapter 6: Molecular crystals and crystalline thin films for photonics
• Chapter 7: Charge generation and transport in organic materials
• Chapter 8: Optical, photoluminescent and electroluminescent properties of organic materials
• Chapter 9: Nonlinear optical properties of organic materials
• Chapter 10: Ultrafast intrachain exciton dynamics in π-conjugated polymers
• Chapter 11: Ultrafast charge carrier dynamics in organic (opto)electronic materials
• Chapter 12: Short-pulse induced photocurrent and photoluminescence in organic materials
• Chapter 13: Conductivity measurements of organic materials using field-effect transistors (FETs) and space-charge-limited current (SCLC) technique
• Chapter 14: Charge transport features in disordered organic materials measured by time-of-fl ight (TOF), xerographic discharge (XTOF) and charge extraction by linearly increasing voltage (CELIV) techniques
• Chapter 15: Surface enhanced Raman scattering (SERS) characterization of metal–organic interactions
• Chapter 16: Second harmonic generation (SHG) as a characterization technique and phenomological probe for organic materials
• Chapter 17: Organic solar cells (OSCs)
• Chapter 18: Organic light-emitting diodes (OLEDs)
• Chapter 19: Organic spintronics
• Chapter 20: Organic semiconductors (OSCs) for electronic chemical sensors
• Chapter 21: Organic bioelectronics
• Chapter 22: Organic electronic memory devices
• Chapter 23: Unconventional molecular scale logic devices
• Chapter 24: Photorefractive (PR) polymers and their recent applications
• Chapter 25: Organic waveguides, ultra-low loss demultiplexers and electro-optic (EO) polymer devices
• Index