Hidekazu Yoshizawa

Bio: Hidekazu Yoshizawa is an academic researcher from Massachusetts Institute of Technology. The author has contributed to research in topics: Electronic paper. The author has an hindex of 2, co-authored 2 publications receiving 1336 citations.

An electrophoretic ink for all-printed reflective electronic displays

Abstract: It has for many years been an ambition of researchers in display media to create a flexible low-cost system that is the electronic analogue of paper. In this context, microparticle-based displays1,2,3,4,5 have long intrigued researchers. Switchable contrast in such displays is achieved by the electromigration of highly scattering or absorbing microparticles (in the size range 0.1–5 μm), quite distinct from the molecular-scale properties that govern the behaviour of the more familiar liquid-crystal displays6. Microparticle-based displays possess intrinsic bistability, exhibit extremely low power d.c. field addressing and have demonstrated high contrast and reflectivity. These features, combined with a near-lambertian viewing characteristic, result in an ‘ink on paper’ look7. But such displays have to date suffered from short lifetimes and difficulty in manufacture. Here we report the synthesis of an electrophoretic ink based on the microencapsulation of an electrophoretic dispersion8. The use of a microencapsulated electrophoretic medium solves the lifetime issues and permits the fabrication of a bistable electronic display solely by means of printing. This system may satisfy the practical requirements of electronic paper.

Heterogeneous display elements and methods for their fabrication

Abstract: Optically heterogeneous display elements utilize fused pigment particles, which may be manufactured with polymer shells having desired charge, photoresponse, or density characteristics. The particles may be microencapsulated prior to formation of the display element, so that the element is formed internally within the container in which it is permanently housed. The element may function as a bichromal display, a light valve, or a programmable magnetic element.

Organic Thin Film Transistors for Large Area Electronics

Abstract: Organic thin-film transistors (OTFTs) have lived to see great improvements in recent years. This review presents new insight into conduction mechanisms and performance characteristics, as well as opportunities for modeling properties of OTFTs. The shifted focus in research from novel chemical structures to fabrication technologies that optimize morphology and structural order is underscored by chapters on vacuum-deposited and solution-processed organic semiconducting films. Finally, progress in the growing field of the n-type OTFTs is discussed in ample detail. The Figure, showing a pentacene film edge on SiO2, illustrates the morphology issue.

Semiconducting π-conjugated systems in field-effect transistors: a material odyssey of organic electronics.

Abstract: Since the discovery of highly conducting polyacetylene by Shirakawa, MacDiarmid, and Heeger in 1977, π-conjugated systems have attracted much attention as futuristic materials for the development and production of the next generation of electronics, that is, organic electronics. Conceptually, organic electronics are quite different from conventional inorganic solid state electronics because the structural versatility of organic semiconductors allows for the incorporation of functionality by molecular design. This versatility leads to a new era in the design of electronic devices. To date, the great number of π-conjugated semiconducting materials that have either been discovered or synthesized generate an exciting library of π-conjugated systems for use in organic electronics. 11 However, some key challenges for further advancement remain: the low mobility and stability of organic semiconductors, the lack of knowledge regarding structure property relationships for understanding the fundamental chemical aspects behind the structural design, and realization of desired properties. Organic field-effect transistors (OFETs) are a kind of device consisting of an organic semiconducting layer, a gate insulator layer, and three terminals (drain, source, and gate electrodes). OFETs are not only essential building blocks for the next generation of cheap and flexible organic circuits, but they also provide an important insight into the charge transport of πconjugated systems. Therefore, they act as strong tools for the exploration of the structure property relationships of πconjugated systems, such as parameters of field-effect mobility (μ, the drift velocity of carriers under unit electric field), current on/off ratio (the ratio of the maximum on-state current to the minimum off-state current), and threshold voltage (the minimum gate voltage that is required to turn on the transistor). 17 Since the discovery of OFETs in the 1980s, they have attracted much attention. Research onOFETs includes the discovery, design, and synthesis of π-conjugated systems for OFETs, device optimization, development of applications in radio frequency identification (RFID) tags, flexible displays, electronic papers, sensors, and so forth. It is beyond the scope of this review to cover all aspects of π-conjugated systems; hence, our focus will be on the performance analysis of π-conjugated systems in OFETs. This should make it possible to extract information regarding the fundamental merit of semiconducting π-conjugated materials and capture what is needed for newmaterials and what is the synthesis orientation of newπ-conjugated systems. In fact, for a new science with many practical applications, the field of organic electronics is progressing extremely rapidly. For example, using “organic field effect transistor” or “organic field effect transistors” as the query keywords to search the Web of Science citation database, it is possible to show the distribution of papers over recent years as shown in Figure 1A. It is very clear

Flexible active-matrix displays and shift registers based on solution-processed organic transistors.

Abstract: At present, flexible displays are an important focus of research1,2,3 Further development of large, flexible displays requires a cost-effective manufacturing process for the active-matrix backplane, which contains one transistor per pixel One way to further reduce costs is to integrate (part of) the display drive circuitry, such as row shift registers, directly on the display substrate Here, we demonstrate flexible active-matrix monochrome electrophoretic displays based on solution-processed organic transistors on 25-μm-thick polyimide substrates The displays can be bent to a radius of 1 cm without significant loss in performance Using the same process flow we prepared row shift registers With 1,888 transistors, these are the largest organic integrated circuits reported to date More importantly, the operating frequency of 5 kHz is sufficiently high to allow integration with the display operating at video speed This work therefore represents a major step towards 'system-on-plastic'

Organic thin-film transistors: a review of recent advances

Abstract: In this paper we review recent progress in materials, fabrication processes, device designs, and applications related to organic thin-film transistors (OTFTs), with an emphasis on papers published during the last three years. Some earlier papers that played an important role in shaping the OTFT field are included, and a number of previously published review papers that cover that early period more completely are referenced. We also review in more detail related work that originated at IBM during the last four years and has led to the fabrication of high-performance organic transistors on flexible, transparent plastic substrates requiring low operating voltages.