Download or read book Studies of Electronic Transport in Novel Smectic and Discotic Liquid Crystalline Organic Semiconductors written by Naresh Man Shakya and published by . This book was released on 2010 with total page 242 pages. Available in PDF, EPUB and Kindle. Book excerpt: Organic semiconductors(OSs) have stirred huge commercial interest due to their potential applications in electronic and optoelectronic devices such as field effect transistors, photovoltaic cells, and organic light-emitting diodes. Major benefits of OSs over conventional semiconductors include mechanical flexibility, low temperature processing, very low cost, and ease of fabrication in large area electronic devices on plastic and paper substrates. Liquid crystals (LCs) are particularly interesting classes of OSs, both from the standpoints of fundamental physics and practical applications. Systems we studied include a thiophene-benzene-thiophene-based smectic (1,4-di-(5-n-tridecylthien-2-yl)-benzene). This material exhibited polaron band behavior with very impressive hole transport (> 0.1 cm^2/Vs with the smectic-F phase templating large domains of more ordered phases with very large mobilities. The mobilities are high enough to be of practical interest. Another project involved calamitic LCs with pyridine-thiophene-thiophene-pyridine cores (5, 5'-di-(alkyl-pyridin-yl)-2, 2' bithiophenes). We found both electron and hole mobilities to be strongly electric field dependent but very weakly dependent on temperature. Pyridine-based LCs often exhibit very high order smectic phases and are therefore of interest as OSs. However, the mobilities of these materials were found quite low, even in high-order phases. We were able to describe some part of our data using Basseler's theory of hopping conduction in disordered systems. We also studied charge transport in a triphenylene-based discotic LC (1-nitro-2, 3, 6, 7, 10, 11-hexakis (pentyloxy) triphenylene). This material showed strong temperature and field dependent hole mobilities described by disorder dominated one-dimensional hopping. Since the columnar phase exists over a wide range of temperatures, such photo-conducting materials may be very useful for applications in electronics. Finally, we developed a technique to measure charge carrier mobility in freely suspended films of LCs in high vacuum. Here, the external field can be coupled easily to the molecular order, no electrodes contact the sample, and extremely high voltages can be applied. Also, both hole and electron mobility (which depends on high purity and absence of oxygen), and samples with a very wide range of thickness may be studied.

Download or read book Charge Transport in Liquid Crystalline Smectic and Discotic Organic Semiconductors written by Sanjoy Paul and published by . This book was released on 2016 with total page 205 pages. Available in PDF, EPUB and Kindle. Book excerpt: Organic electronics offer the possibility of producing low cost, flexible, and large area electronics. Organic semiconductors (OSCs) (organic polymers and crystals), used in organic electronics, are promising materials for novel optical and electronic devices such as organic light emitting diodes, organic field effect transistors, organic sensors, and organic photovoltaics (OPVs). OSCs are composed of molecules weakly held together via van der Walls forces rather than covalent bonds as in the case of inorganic semiconductors such as Si. The combined effect of small wave function overlap, spatial and energetic disorder in organic semiconducting materials lead to localization of charge carriers and, in many cases, hopping conduction. OSCs also differ from conventional semiconductors in that charges photogeneration (e.g., in OPVs) proceeds via the production, diffusion, and dissociation of excitons. Liquid crystalline OSCs (LCOSCs) are semiconductors with phases intermediate between the highly ordered crystalline and completely disordered liquid phases. These materials offer many advantages including facile alignment and the opportunity to study the effects of differing intermolecular geometries on transfer integrals, disorder-induced trapping, charge mobilities, and photogeneration efficiency. In this dissertation work, we explored the photogeneration and charge transport mechanisms in a few model smectic and discotic LCs to better understand the governing principles of photogeneration and charge transport using conventional and novel methods based on the pulsed laser time-of-flight charge carrier transport technique. Four major interrelated topics were considered in this research. First, a sample of smectic LC was aligned in order to compare the resulting hole mobility to that of an unaligned sample, with the aim of understanding how the intermolecular alignment over large length scales affects the hopping probability. The role of the polarization of the photogenerating light was also explored in the context of these anisotropic systems. Next, the photogeneration and charge transport was investigated as a function of temperature, electric field, the wavelength and intensity of photogenerating light. Different exciton dissociation interfaces between the electrode and the LC to probe the details of the mechanism of excitonic dissociation (e.g., surface mediated generation vs. exciton-exciton fusion) were explored. Next, we have also developed a new method of spatially resolving the photogeneration and transport mechanisms in inhomogeneous OSCs called "scanning time of flight microscopy (STOFm)" which simultaneously obtains 2d images of transport coefficients and polarized transmittance. The STOFm was extensively used to study charge transport in various structured semiconductors: smectics, discotics, as well as in phase separated LC/polymer structures. Finally, this work involves characterization and analysis of transport in a number of new phenyl-naphthalene LC OSCs.

Download or read book Liquid Crystalline Semiconductors written by Richard J. Bushby and published by Springer Science & Business Media. This book was released on 2012-11-28 with total page 282 pages. Available in PDF, EPUB and Kindle. Book excerpt: This is an exciting stage in the development of organic electronics. It is no longer an area of purely academic interest as increasingly real applications are being developed, some of which are beginning to come on-stream. Areas that have already been commercially developed or which are under intensive development include organic light emitting diodes (for flat panel displays and solid state lighting), organic photovoltaic cells, organic thin film transistors (for smart tags and flat panel displays) and sensors. Within the family of organic electronic materials, liquid crystals are relative newcomers. The first electronically conducting liquid crystals were reported in 1988 but already a substantial literature has developed. The advantage of liquid crystalline semiconductors is that they have the easy processability of amorphous and polymeric semiconductors but they usually have higher charge carrier mobilities. Their mobilities do not reach the levels seen in crystalline organics but they circumvent all of the difficult issues of controlling crystal growth and morphology. Liquid crystals self-organise, they can be aligned by fields and surface forces and, because of their fluid nature, defects in liquid crystal structures readily self-heal. With these matters in mind this is an opportune moment to bring together a volume on the subject of ‘Liquid Crystalline Semiconductors’. The field is already too large to cover in a comprehensive manner so the aim has been to bring together contributions from leading researchers which cover the main areas of the chemistry (synthesis and structure/function relationships), physics (charge transport mechanisms and optical properties) and potential applications in photovoltaics, organic light emitting diodes (OLEDs) and organic field-effect transistors (OFETs). This book will provide a useful introduction to the field for those in both industry and academia and it is hoped that it will help to stimulate future developments.

Download or read book Self Organized Organic Semiconductors written by Quan Li and published by John Wiley & Sons. This book was released on 2011-03-03 with total page 376 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book focuses on the exciting topic on self-organized organic semiconductors – from materials to device applications. It offers up-to-date and accessible coverage of self-organized semiconductors for organic chemistry, polymer science, liquid crystals, materials science, material engineering, electrical engineering, chemical engineering, optics, optic-electronics, nanotechnology and semiconductors. Chapters cover chemistry, physics, processing, and characterization. The applications include photovoltaics, light-emitting diodes (LEDs), and transistors.

Download or read book Crystal Growth and Charge Carrier Transport in Liquid Crystals and Other Novel Organic Semiconductors written by Chandra Prasad Pokhrel and published by . This book was released on 2009 with total page 180 pages. Available in PDF, EPUB and Kindle. Book excerpt: Due to the many advantages of organic semiconductors over their inorganic counterparts, there is a strong and growing interest in their development. However, the large intermolecular spacing and other factors in organics result in a band structure that is narrow and often thermally disrupted, introducing disorder in the system and adversely affecting the conduction of charge. In this dissertation, we concentrate on three factors that influence the motion of charge: disorder, ionic impurities, and molecular design (and, in particular, the presence of pyridine). We discuss charge carrier mobility measurement in different organic semiconductors ranging from relatively ordered liquid crystalline systems to a highly disordered glassy material. Several theoretical approaches are used to analyze the results. For example, in a terpyridine-based high-order smectic liquid crystal we found surprisingly small, Poole-Frenkel mobilities (log(mobility) ̃E1/2) which may naively be described by either the Scher-Montroll (non-Gaussian transport) or Bassler's Gaussian transport model. However, the transient current traces did not comply with the universality and logarithmic slope predictions of the non-Gaussian model, but do follow the predictions of Bassler's model of Gaussian conduction. This various roles of diagonal (site energy) and off-diagonal (transfer integral) disorder are discussed. In the organic glassy material, the energy disorder of the transport sites plays the central role in determining the mobility. Using the spatially correlated disorder model of Kenkre, Dunlap, and coworkers, we are able to extract reasonable materials' parameters such as the Gaussian width of the hopping site energy distribution and the molecular dipole moment. Impurities also play several essential roles in organic semiconductors. Here we concentrate on itinerant ions in liquid crystalline semiconductors. Due to the low viscosity of the liquid crystalline system, mobile ions may influence the effective charge carrier mobility, lowering the device performance and making extraction of the intrinsic mobility difficult. The effect of ions on charge transport, their temporal and spatial distribution, a technique to measure the intrinsic carrier mobility, and the corresponding theory is presented using a sample discotic liquid crystal material (HAT5), a quasi one-dimensional transport medium.

Download or read book Liquid Crystals in Photovoltaics written by Dr. Luz J Martinez-Miranda and published by CRC Press. This book was released on 2021-06-30 with total page 99 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book explores why the properties of liquid crystals make them ideal for use in photovoltaic applications. It achieves this by presenting a description of the properties of liquid crystals and how their electronic properties compare to that of polymers used in organic photovoltaics. It explores how the type of liquid crystal chosen can help in improving the efficiency of the photovoltaics. It compares experimental and theoretical ways in which the efficiency is directly or indirectly estimated between the organic photovoltaics and the organic photovoltaics that contain a liquid crystal. It first introduces liquid crystals and their different varieties, before reviewing their electronic transfer properties and how they can improve efficiency. It is an ideal text for graduate students and young researches considering entering the area of photovoltaics - specifically, organic photovoltaics – who do not yet have knowledge of this field. Introduces the field of liquid crystals and provides basic information to those new to the field, in a concise and visual manner Describes which characteristics of a liquid crystal are most advantageous to use in photovoltaics Provides basic knowledge of photovoltaics for those who do not have previous knowledge of how they behave electronically

Download or read book Liquid Crystals Beyond Displays written by Quan Li and published by John Wiley & Sons. This book was released on 2012-05-29 with total page 598 pages. Available in PDF, EPUB and Kindle. Book excerpt: The chemistry, physics, and applications of liquid crystals beyond LCDs Liquid Crystals (LCs) combine order and mobility on a molecular and supramolecular level. But while these remarkable states of matter are most commonly associated with visual display technologies, they have important applications for a variety of other fields as well. Liquid Crystals Beyond Displays: Chemistry, Physics, and Applications considers these, bringing together cutting-edge research from some of the most promising areas of LC science. Featuring contributions from respected researchers from around the globe, this edited volume emphasizes the chemistry, physics, and applications of LCs in areas such as photovoltaics, light-emitting diodes, filed-effect transistors, lasers, molecular motors, nanophotonics and biosensors. Specific chapters look at magnetic LCs, lyotropic chromonic LCs, LC-based chemical sensors, LCs in metamaterials, and much more. Introducing readers to the fundamentals of LC science through the use of illustrative examples, Liquid Crystals Beyond Displays covers not only the most recent research in the myriad areas in which LCs are being utilized, but also looks ahead, addressing potential future developments. Designed for physicists, chemists, engineers, and biologists working in academia or industry, as well as graduate students specializing in LC technology, this is the first book to consider LC applications across a wide range of fields.

Download or read book Organic Electronics II written by Hagen Klauk and published by John Wiley & Sons. This book was released on 2012-03-26 with total page 443 pages. Available in PDF, EPUB and Kindle. Book excerpt: Like its predecessor this book is devoted to the materials, manufacturing and applications aspects of organic thin-film transistors. Once again authored by the most renowned experts from this fascinating and fast-moving area of research, it offers a joint perspective both broad and in-depth on the latest developments in the areas of materials chemistry, transport physics, materials characterization, manufacturing technology, and circuit integration of organic transistors. With its many figures and detailed index, this book once again also serves as a ready reference.

Download or read book Electronic Processes in Organic Electronics written by Hisao Ishii and published by Springer. This book was released on 2015-01-07 with total page 427 pages. Available in PDF, EPUB and Kindle. Book excerpt: The book covers a variety of studies of organic semiconductors, from fundamental electronic states to device applications, including theoretical studies. Furthermore, innovative experimental techniques, e.g., ultrahigh sensitivity photoelectron spectroscopy, photoelectron yield spectroscopy, spin-resolved scanning tunneling microscopy (STM), and a material processing method with optical-vortex and polarization-vortex lasers, are introduced. As this book is intended to serve as a textbook for a graduate level course or as reference material for researchers in organic electronics and nanoscience from electronic states, fundamental science that is necessary to understand the research is described. It does not duplicate the books already written on organic electronics, but focuses mainly on electronic properties that arise from the nature of organic semiconductors (molecular solids). The new experimental methods introduced in this book are applicable to various materials (e.g., metals, inorganic and organic materials). Thus the book is also useful for experts working in physics, chemistry, and related engineering and industrial fields.

Download or read book The Non Local Density of States of Electronic Excitations in Organic Semiconductors written by Carl. R Poelking and published by Springer. This book was released on 2017-10-24 with total page 142 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book focuses on the microscopic understanding of the function of organic semiconductors. By tracing the link between their morphological structure and electronic properties across multiple scales, it represents an important advance in this direction. Organic semiconductors are materials at the interface between hard and soft matter: they combine structural variability, processibility and mechanical flexibility with the ability to efficiently transport charge and energy. This unique set of properties makes them a promising class of materials for electronic devices, including organic solar cells and light-emitting diodes. Understanding their function at the microscopic scale – the goal of this work – is a prerequisite for the rational design and optimization of the underlying materials. Based on new multiscale simulation protocols, the book studies the complex interplay between molecular architecture, supramolecular organization and electronic structure in order to reveal why some materials perform well – and why others do not. In particular, by examining the long-range effects that interrelate microscopic states and mesoscopic structure in these materials, the book provides qualitative and quantitative insights into e.g. the charge-generation process, which also serve as a basis for new optimization strategies.

Download or read book Structural and Charge Transporting Properties of Pure Liquid Crystalline Organic Semiconductors and Composites for Applications in Organic Electronics written by Kirill Kondratenko and published by . This book was released on 2019 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: This thesis is dedicated to various aspects of liquid crystalline (LC) organic semiconductors (OSCs) in regard to their applications in the field of organic electronics. The first part of this work deals with a well-known LC OSC based on phenyl-naphtalene. Two major ways of performance improvement are proposed and investigated : stabilization of LC structure by in situ photo-polymerization and introduction of electron acceptor doping impurity. In the first case, the influence of polymer network on mesophase order and charge transport is investigated by conventional experimental techniques and Time-Of-Flight (TOF) mobility measurements. Fot the doped materials, ab initio calculations are employed to predict their spectroscopic properties which is exhaustively compared with the experimental data obtained by optical and vibrational spectroscopy. The charge transport is studied by TOF method in the mesophase, while crystalline phase is investigated via conductive atomic force microscopy. A prototype of organic field effect transistor (OFET) is prepared to obtain an estimate of performance for a relevant real-world application. The second part of this work includes design and synthesis of a novel LC semiconductor based on anthracene, additional attention is made to obtain an easy-to-make and low production cost material. Noval molecule is fully characterized : molecular structure is confirmed by relevant techniques ; frontier molecular energy levels are studied by optical spectroscopy and cyclic voltammetry and confronted to values obtaines via ab initio calculations ; mesophase properties are investigated by optical microscopy and scanning calorimetry. charge transporting properties are characterized by means of an OFET device : it is found that new anthracene-molecule exhibits significant improvement of field-effect hole mobility over previously studied phenyl naphtalene derivative. Finally, photoconductive properties of the novel material are addressed in order to investigate its potential applications to organic phototransistors.

Download or read book Electronic Transport Studies on Hybrid Organic inorganic Semiconductor Devices on the Nanoscale written by Simon K. Pfaehler and published by . This book was released on 2019 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Linguistique et documentation written by Maurice Coyaud and published by . This book was released on 1972 with total page 173 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Nanoscience with Liquid Crystals written by Quan Li and published by Springer Science & Business. This book was released on 2014-04-17 with total page 431 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book focuses on the exciting topic of nanoscience with liquid crystals: from self-organized nanostructures to applications. The elegant self-organized liquid crystalline nanostructures, the synergetic characteristics of liquid crystals and nanoparticles, liquid crystalline nanomaterials, synthesis of nanomaterials using liquid crystals as templates, nanoconfinement and nanoparticles of liquid crystals are covered and discussed, and the prospect of fabricating functional materials is highlighted. Contributions, collecting the scattered literature of the field from leading and active players, are compiled to make the book a reference book. Readers will find the book useful and of benefit both as summaries for works in this field and as tutorials and explanations of concepts for those just entering the field. Additionally, the book helps to stimulate future developments.

Download or read book Fluids Colloids and Soft Materials written by Alberto Fernandez-Nieves and published by John Wiley & Sons. This book was released on 2016-05-09 with total page 444 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book presents a compilation of self-contained chapters covering a wide range of topics within the broad field of soft condensed matter. Each chapter starts with basic definitions to bring the reader up-to-date on the topic at hand, describing how to use fluid flows to generate soft materials of high value either for applications or for basic research. Coverage includes topics related to colloidal suspensions and soft materials and how they differ in behavior, along with a roadmap for researchers on how to use soft materials to study relevant physics questions related to geometrical frustration.

Download or read book SPSJ Annual Meeting written by Kōbunshi Gakkai (Japan) and published by . This book was released on 2001 with total page 802 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Book of Abstracts written by and published by . This book was released on 2000 with total page 776 pages. Available in PDF, EPUB and Kindle. Book excerpt: