| POLYMERS Vol.66 No.7 |
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COVER STORY
Polymers Related to Flexible Electronic Devices |
| COVER STORY: Highlight Reviews |
| Polymers in Reflective Displays | Norihisa KOBAYASHI |
| <Abstract> Reflective displays, so-called “e-paper”, have been attracting a lot of interest as next generation displays with low energy consumption and excellent visibility under sunlight condition. A number of mechanisms have been proposed as reflective displays for commercial use. In this article, the microencapsulated electrophoretic display (EPD), which is a leading technology in reflective displays and the electrochromic system (ECD), which is expected to show a full color representation are reviewed particularly in relation to the function of polymers in the devices. Keywords: Reflective Display / e-Paper / Microcapsule / Electrophoretic / Electrochromism / Silver Deposition / Plasmon |
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| Electromechanically Active Polymer Soft Actuators | Hidenori OKUZAKI |
| <Abstract> Polymers that undergo shape and dimensional changes in response to electric stimuli can be applied to flexible robots, soft actuators, and artificial muscles. A variety of electromechanically active polymer (EAP) soft actuators, such as ionic polymers, conductive polymers, carbon nanotubes, super-coiled polymers, dielectric elastomers/gels, liquid crystalline elastomers/gels, piezoelectric polymers, and electrostatic films, has so far been investigated for practical applications. Here we introduce recent trends of research and development and future perspective of the EAP soft actuators. Keywords: Electromechanically Active Polymer / Soft Actuator / Ionic Polymer Metal Composite / Conductive Polymer / Dielectric Elastomer / Super-Coiled Polymer / Compliant Electrode / PEDOT：PSS |
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| Trend of Solution-Processable Organic Semiconductor Development and Applications | Shizuo TOKITO |
| <Abstract> This article reports on the latest trend for small-molecular and polymer semiconductors and their molecular orientations in thin films prepared from solutions as well as electrical characteristics of printed organic thin-film transistors (TFTs). The applications of the printed organic TFT devices to integrated circuits are also described including advanced finely-printing technology. Keywords: Organic Semiconductors / Printed Electronics / TFT / Integrated Circuits |
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| COVER STORY: Topics and Products |
| Device-Less Evaluation of Organic Photovoltaics | Akinori SAEKI |
| <Abstract> An organic photovoltaic (OPV) cell is a flexible, light-weight electric device that consists of earth-abundant non-toxic elements and converts sunlight energy into electricity. A remarkable improvement in power conversion efficiency (PCE) has been achieved through the use of innovative materials and device structures. However, a reliable technique for the rapid screening of the materials and processes is a strong demand towards faster development in this area. This article reviews such a versatile evaluation technique for bulk heterojunction (BHJ) OPVs, which was realized by using time-resolved microwave conductivity (TRMC). A nanosecond monochromatic laser pulse or microsecond white light pulse from a Xe flash-lamp is used as the excitation. This device-less evaluation of OPV allows a rapid screening of processing conditions and materials without requiring tedious fabrication of the actual device. TRMC also demonstrates the feasibility of the quantification of the hole transfer yield from the organic-inorganic perovskite to hole transfer layer and could offer an alternative way to characterize materials for photocatalysts and light-emitting diodes. Keywords: Organic Solar Cell / Conjugated Polymer / Time-Resolved Microwave Conductivity (TRMC) / Charge Carreir Mobility / Peovskite Solar Cell / Hole Transfer Layer |
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| Development of Organic Photovoltaic Cells in TORAY | Daisuke KITAZAWA |
| <Abstract> Organic photovoltaic cells (OPVs) based on a blend film of an electron-donor polymer and an electron acceptor material have attracted much attention because of their potential application in flexible and lightweight solar cells, which could be fabricated by cost-effective production such as roll-to-roll printing. Our current major challenges for commercialization of OPVs are to improve the power conversion efficiency (PCE) and device stabilities. We have been developing high performanece OPVs, which showed high power conversion efficiency of up to 10% under an illumination of AM 1.5 G at 100 mW/cm2 and high stability beyond 1,000 h under light- (successive 1 sun irradiation, room temperature) and thermal (dark, 85℃) test conditions. Keywords: Organic Photovoltaic Cells / Electron Donor Material / Power Conversion Efficiency / Stability |
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| Piezoelectric Chiral Polymer: Film, Fabric, Decorated Braiding Code | Yoshiro TAJITSU |
| <Abstract> We have been jointly developing environmentally conscious polylactic-acid (PLA) piezoelectric materials for a number of years, including a flexible piezoelectric film. Piezoelectricity is the generation of electric charges by certain dielectric materials in response to mechanical stress. Recently, we developed wearable sensors in the shapes of Japanese traditional braided cords, known as kumihimo, using PLA piezoelectric fiber. The new piezoelectric kumihimo wearable sensors use the method of kumihimo’s technical art and can detect user motions such as elongation and contraction, bending and extension, and twisting. The softness and flexibility of kumihimo shapes enable the sensors to be fashioned in a wide variety of thicknesses, lengths and shapes. Other useful features include low noise, high sensitivity and solderless construction enable easy connection to devices with a small connector. Kumihimo knotting and flexibility enable fashionable sensors to be worn as accessories, such as chokers and necklaces that detect human movements including pulse wave, swallowing or coughing. Keywords: Piezoelectricity / Chirality / Poly-Lactic Acid / PLLA / Film / Fabric / Decorated Braiding Code |
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| Polymer Science and I: A Personal Account |
| Under Exploration | Kazuhiro NAKABAYASHI |
| <Abstract> This essay describes the author’s research career in four institutions, involving foreign institutions. Through the research experience under various environments, the author is now seeking original research for the next decade. However, a little more time is necessary to find it. So, it is still under exploration……. |
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| Front-Line Polymer Science |
| Mechanical Properties of Flexible Materials | Atsushi SHISHIDO, Norihisa AKAMATSU |
| <Abstract> In recent years, soft matter has been extensively studied for wide applications: wearable devices, displays, and so on. Soft matter has a special feature in its three-dimensional flexibility, and its detailed deformation behavior is of great importance from the viewpoint of materials design. We introduce recent progress on material deformation analysis methods for flexible electronics. Keywords: Flexible Device / Soft Material / Mechanical Property |
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