This book provides a systematic presentation of the principles and practices behind the synthesis and functionalization of graphene and grapheme oxide (GO), as well as the fabrication techniques for transparent conductors from these materials. Transparent conductors are used in a wide variety of photoelectronic and photovoltaic devices, such as liquid crystal displays (LCDs), solar cells, optical communication devices, and solid-state lighting. Thin films made from indium tin oxide (ITO) have thus far been the dominant source of transparent conductors, and now account for 50% of indium consumption. However, the price of Indium has increased 1000% in the last 10 years. Graphene, a two-dimensional monolayer of sp2-bonded carbon atoms, has attracted significant interest because of its unique transport properties. Because of their high optical transmittance and electrical conductivity, thin film electrodes made from graphene nanosheets have been considered an ideal candidate to replace expensive ITO films. Graphene for Transparent Conductors offers a systematic presentation of the principles, theories and technical practices behind the structure–property relationship of the thin films, which are the key to the successful development of high-performance transparent conductors. At the same time, the unique perspectives provided in the applications of graphene and GO as transparent conductors will serve as a general guide to the design and fabrication of thin film materials for specific applications.
Edited by well-known pioneers in the field, this handbook and ready reference provides a comprehensive overview of transparent conductive materials with a strong application focus. Following an introduction to the materials and recent developments, subsequent chapters discuss the synthesis and characterization as well as the deposition techniques that are commonly used for energy harvesting and light emitting applications. Finally, the book concludes with a look at future technological advances. All-encompassing and up-to-date, this interdisciplinary text runs the gamut from chemistry and materials science to engineering, from academia to industry, and from fundamental challenges to readily available applications.
In this second volume in the first book series on nanocarbons for advanced applications the highly renowned series and volume editor has put together a top author team of internationally acclaimed experts on carbon materials. Divided into three major parts, this reference provides a current overview of the design, synthesis, and characterization of nanocarbons, such as carbon nanotubes, fullerenes, graphenes, and porous carbons for energy conversion applications. It covers such varied topics as electrocatalysts for oxygen reduction reactions in the different types of fuel cells, metal-air batteries and electrode materials for photovoltaic devices, as well as photocatalysts, electrocatalysts and photoelectrocatalysts for water splitting. Throughout, the authors highlight the unique aspects of nanocarbon materials in these fields, with a particular focus on the physico-chemical properties which lead to enhanced device performances.
Due to its unique properties, graphene oxide has become one of the most studied materials of the last decade and a great variety of applications have been reported in areas such as sensors, catalysis and biomedical applications. This comprehensive volume systematically describes the fundamental aspects and applications of graphene oxide. The book is designed as an introduction to the topic, so each chapter begins with a discussion on fundamental concepts, then proceeds to review and summarize recent advances in the field. Divided into two parts, the first part covers fundamental aspects of graphene oxide and includes chapters on formation and chemical structure, characterization methods, reduction methods, rheology and optical properties of graphene oxide solutions. Part Two covers numerous graphene oxide applications including field effect transistors, transparent conductive films, sensors, energy harvesting and storage, membranes, composite materials, catalysis and biomedical applications. In each case the differences and advantages of graphene oxide over its non-oxidised counterpart are discussed. The book concludes with a chapter on the challenges of industrial-scale graphene oxide production. Graphene Oxide: Fundamentals and Applications is a valuable reference for academic researchers, and industry scientists interested in graphene oxide, graphene and other carbon materials.
This book presents fabrication approaches that could be adapted for the high-throughput and low-cost manufacturing of the proposed transparent electrode. It proposes and demonstrates a new type of embedded metal-mesh transparent electrode (EMTE) that offers superior electrical, optical, and mechanical properties. The structure of the EMTE allows thick metal mesh to be used (for high conductivity) without sacrificing surface smoothness. In addition, the embedded structure improves the EMTE’s mechanical stability under high bending stress, as well as its chemical stability in ambient environments. These design aspects are then shown to be suitable for larger electrode areas, narrower metal-mesh line widths, and a wide range of materials, and can easily be adapted to produce flexible and even stretchable devices. In closing, the book explores the practical applications of EMTEs in flexible bifacial dye-sensitized solar cells and transparent thin-film heaters, demonstrating their outstanding performance.
This book discusses the important technological aspects of the growth of GaN single crystals by HVPE, MOCVD, ammonothermal and flux methods for the purpose of free-standing GaN wafer production.
The Organic photovoltaic cell (OPV) is a promising technology because of its potential for low-cost high-throughput roll-to-roll manufacturing. Significant improvements have been achieved in power conversion efficiency (PCE) of OPV cells during last two decades. While recent progress in raising the PCE has been encouraging, the PCE of organic solar cells is still limited and needs to be improved to meet the requirement for commercial applications. Further improvements in both material properties and device architectures are necessary. Photocurrent generation in an OPV cell is fundamentally different from the process that takes place in their inorganic counterparts. A detailed understanding of the operation mechanisms of OPV cells and optimization of the fundamental electronic properties of the system (or material) are critical. In this work, I will first discuss major factors that limit the efficiency of bilayer OPV cells, such as exciton binding energy, exciton diffusion length, charge separation and open-circuit voltage. The exciton binding energy is one of the key parameters that govern the operation of OPV cells, and determines the required energy band offset between donor and acceptor, and thus the achievable open-circuit voltage of the donor-acceptor combination. Exciton diffusion is a main bottleneck limiting photocurrent of a bi-layer OPV cell, which depends on material properties and film morphology. The energy loss between optical excitation and extracted electrical power is mainly due to the energy band offset between donor and acceptor in OPV cells. The PCE limit for single junction OPV cell can be estimated based on the findings. In the second part of this work, I will focus on transparent conductors, which are essential components of thin-film optoelectronic devices. Sputtered Indium-Tin-Oxide (ITO) is currently the most commonly used transparent electrode material, but it has a number of shortcomings. There is a clear need for alternative transparent electrodes whose optical and electrical performance is similar to that of ITO but without its drawbacks. The next generation transparent conductor should also be lightweight, flexible, cheap, environmental attractive, and compatible with large-scale manufacturing methods. I will discuss the possibility of using graphene thin films as a replacement for ITO. Theoretical estimates indicate that graphene thin films are promising transparent electrodes for thin-film optoelectronic devices, with an unmatched combination of sheet resistance and transparency. For the first time, we demonstrated that solution-processed graphene thin films can serve as transparent conductive anodes for both OPV cells and organic light-emitting diodes (OLEDs). The graphene electrodes were deposited on quartz substrates by spin-coating of an aqueous dispersion of functionalized graphene, followed by a vacuum anneal step to reduce the sheet resistance. Small molecular weight organic materials and a metal cathode were directly deposited on the graphene anodes, resulting in devices with a performance comparable to control devices on ITO transparent anodes. Device modeling has been explored to compare the performance between graphene-based device and ITO-based control device. Transfer of graphene films to a foreign flexible substrate was also demonstrated which opens up new opportunities for low-cost flexible organic opto-electronics.
