Top-gate organic FETs with embedded source-drain electrodes using a printable organic semiconductor, 2, 7-dioctyl  benzothieno [3, 2-b]  benzothiophene (C8-BTBT), have been fabricated. The top-gate C8-BTBT FETs with embedded electrodes show better electrical performance : higher mobilities (4.9cm2/Vs) and lower threshold voltages (0.6V) in comparison with those of the top-gate FETs with a conventional electrode configuration. Such high mobility is comparable to that of microcrystalline silicon FETs.
A single-layer organic photoreceptor for electrophotography with relatively low concentrations of phthalocyanine pigments dispersed in a suitable insulating binder polymer, which shows the induction effect is generally referred to as a high gamma photoreceptor. The surface electrical charge is injected into the photoconductive layer through adsorption of the chemical substance generated on the free surface during the corona discharge. The overcoat layer was validated to be beneficial experimentally as well as theoretically in order to protect the high gamma photoreceptor from the surface charge injection. The photoinduced and dark discharge characteristics of x-type metal-free phthalocyanine pigment with polyester binder polymer overcoated high gamma photoreceptor are clearly explained with theoretical model by considering the structural trap model.
Toner display based on an electrical movement of black and white charged toners has been investigated. Two types of black and white insulating toners charged in the different electric polarity are enclosed between a two transparent electrodes. The particle movement is controlled by the external electric field applied between two transparent electrodes. The black toner is attached on the cathode by an electrostatic force across the insulating layer to display a black image. The black toner can be put back to the counter electrode and white toner is attached on the anode by applying a reverse electric field to display a white image. The black and white solid images are displayed by the switch of polarity of applied voltage in the toner display cell.
VOCs (volatile organic compounds) arising from fusers in printers, solvent inks in inkjet printers, or wet POD systems cause environmental problems at present. Therefore, efficient elimination technologies are in high demand. In this paper, we will present our novel VOC elimination system based upon thermally activated semiconductors (TASC) characterized by compact, lightweight, and low costs. Because of these appealing features, this system can easily be integrated into office printers or wet POD systems. The TASC technology dates back to our accidental finding that the semiconductor exhibits significant oxidative effects when heated at 350-500°C ; whereas quite inactive at room temperature. The present phenomenon has been applied to the complete decomposition of VOCs. The destruction mechanism is composed of the following three steps : 1. oxidation, i.e. creation of radicals, 2. radical splitting, i. e. fragmentation of the giant molecule, and 3. reaction with oxygen, i. e. complete combustion into H2O and CO2.
One of the reason why silicon-based semiconductor technologies were revolutionary is the ease of controlling the properties and functions. Silicon is naturally abundant as well, and there was no maldistribution of the material. Carbon, on the other hand, is much less abundant (1/1000) compared to silicon. However, it is concentrated in specific locations which makes it easy to mine the material. Carbon atoms can be bonded to each other by either sp, sp2, or sp3 bonding, which lead to various structures compared to silicon with basically sp3 bonding. Owing to the variety of bondings, carbon structure can be controlled to a wide range. Especially nanocarbons with dimensionalities have unique properties which have been attracting lots of interest and has become one of the most active field since the end of 20th century. In the present article, we will overview the basics of nanocarbons and its variants such as fullerenes, nanotubes, and graphenes. Finally, the applications, health and safety research mainly focusing on carbon nanotubes, will be discussed.
This article introduces the method to fabricate a transparent graphene conductive film from graphite powder by a solution process. Chemically oxidized graphite powder was dispersed in water, and it was exfoliated by repeated centrifugation and washing processes to obtain a graphene oxide solution. Successively, a graphene oxide film was prepared by coating a transparent substrate with the prepared solution, and it was chemically and thermally deoxidized to produce a transparent graphene conductive film. To date, organic thin film photovoltaic cells with the graphene transparent electrodes have shown the power conversion efficiency as high as 1.2%. Novel application of graphene oxide to hole-transporting layers and organic/inorganic heterojunction solar cells will be also presented. Finally, I will show the application of solution-processed graphene electrodes to organic thin film field-effect transistors.
In this review, we introduce terahertz (THz) emitters and detectors that utilize the hydrodynamic properties of two-dimensional plasmons in graphene and active plasmonic devices that utilize the interband population inversion and stimulated emission of THz photons enabled by the zero bandgap of graphene. Physical properties of two-dimensional plasmons and operation mechanisms of plasmonic emitters and detectors based on hydrodynamic plasma instability and nonlinearity, which have been studied for compound semiconductor heterostructures, are reviewed, and superiorities of graphene as a channel material are mentioned. The interband population inversion and THz stimulated emission specific to graphene are reviewed, and the active plasmonic waveguide as well as the plasmonic laser are introduced.
Various carbon materials have been prepared by pyrolysis of organic and polymer substances under inert gases and atmospheric pressure conditions. Considering shape, structures, and properties of starting organic substances, various functionalized carbon materials can be prepared. Especially, nano-structurization has been a key process for development of high-performance carbon materials for energy-storage and utilization. In this review paper, approaches for preparations of nano-structured carbon materials from conjugated polymers, woody substances, and cyclodextrin microcubes are summarized. Characteristics of nano-structured and microshape-retaining carbons derived from these substances are also summarized with reference to typical porous carbons and hierarchical nano-structred carbons.
Carbon nanotubes (CNT), having high aspect ratio of several tens nanometer in diameter and several millimeter in length, were spun into continuous yarns. Since CNT, which is a covalently bonded crystal of carbon, has quite high tensile strength and modulus with very low weight density of 2g/cm3, it has been expected to be used in structural materials as a light-weight and strong reinforcing material. However mechanical properties of the CNT yarn, in which CNTs are connected by van der Waals force, is far below that of CNT short fiber. The purpose of the present study is to derive high materials properties from CNT into a macroscopic CNT structure of spun yarn. We describe our fabrication method of the CNT yarns and discuss mechanical properties of the yarns.
Nanocarbon, such as carbon nanofibers (CNTs), carbon nanotubes (CNFs) and graphene, is one of the hottest materials in materials science and nanotechnology fields. They are usually synthesized from gas phase at elevated temperatures, so the synthesis is the high temperature process. By contrast, using low energy (at and below keV range) ion beam technique, CNFs of 10∼30nm in diameter and 1∼2μm in length can be grown on any carbon coated substrates without any catalyst and heating. In this report, the morphological feature, formation mechanism and the growth control of the ion-induced CNFs were dealt with. In addition, their applications to probes for atomic force microscopy and transparent flexible displays were proposed. Also, in situ observation of transmission electron microscopy on CNT and graphene formation from ion induced CNFs by solid phase reaction were demonstrated.