In electrical engineering and electronics of the 21^st century, it has been believed that the role of organic molecular materials is extremely important, in addition to organic dielectrics and semiconductor materials. Therefore it is extremely important and necessary to comprehend precisely the research trend of the Asian countries where become conspicuous remarkably, not to mention Europe and America, and the studies progress rapidly under the interdisciplinary and international cooperation. From such a point of view, being based on the culture peculiar to the location, we have investigated and discussed the characteristics of the study based on application to the next-generation electronics of organic dielectrics, conductive electrical and electronic materials in Asian countries such as China, Korea, India etc. Furthermore, as the engineering system which is necessary to inflect properties and characteristics to have of a structure comprised of organic dielectrics, semiconductors, conductive materials and organic molecular devices in the field of electrical and electronic engineering, to plan development to “engineering of organic-molecular devices” is our goal. The field of organic electronics promises exciting new technologies based on inexpensive and mechanically flexible electronic devices and is now seeing beginning of commercial success.

Liquid crystals can be used as a quality organic semiconductor material, because their intrinsic charge carrier transport is electronic. They show high solubility in organic solvents and easy control of molecular orientation, which helps to fabricate uniform films with good surface morphology. We have developed a novel liquid crystalline organic-semiconductor, 2-decyl-7-phenyl-benzothienobenzothiophene (Ph-BTBT-10), which exhibits highly ordered liquid crystal phase of Smectic E (SmE) phase, from 142℃ to 210℃. Uniform and flat polycrystalline thin films can be easily fabricated by spin-coating technique at a liquid crystalline temperature and cooling down to room temperature. The bottom-gate top-contact type field effect transistors (FETs) with the polycrystalline thin films exhibited high FET mobility of 16.6 cm²/Vs in the average of 12 devices and 22.4 cm²/Vs in the maximum. The FETs exhibited thermal durability up to 200℃ thanks to solid-like nature of the SmE phase.

A novel optical second harmonic generation (SHG) technique that can visualize carrier dynamics in organic materials has been developed on the basis of dielectrics physics approach. Nonlinear polarization induced in organic layers due to the presence of static electric field originated from mobile carriers is directly probed by laser irradiation along with the carrier motion. The visualized carrier dynamics is available for distinguishing carrier species, i.e., electrons and holes, and very helpful to analyze and model carrier behaviors in a variety of organic materials, and also in organic devices such as Organic transistors, Organic electroluminescence devices, Organic solar cells, Organic memory devices and so forth. On comparing with Time of Flight method, the principle of the SHG technique is discussed with some experimental examples.

The concept of using a heterostructure with bilayer oriented conjugated polymer films in organic photodetectors (OPDs) is introduced to provide a useful approach to detect two different wavelengths. The characteristics of the inverted-OPDs based on oriented bilayer fluorene-type polymers of ITO/perylene derivative/ poly(9,9-dioctylfluorene-alt-benzothiadiazole)(F8BT)/poly(9,9-dioctylfluorene)(F8)/MoOx/Ag are investigated. The thickness of an F8BT layer is optimized for polarization-sensitive photodetection. When polarized ultraviolet (blue) light is used, the photocurrent ratio of the parallel to the perpendicular condition reachs a maximum of 1.8 (1.5). We demonstrate the possibility of producing two wavelength polarization-sensitive organic photodetectors. This work is anticipated to be useful for the development of polarization-sensitive OPDs.

In this work, inverted organic thin film solar cells on grating-structured electrode were fabricated by a nanoimprinting technique. First, a TiO₂ layer was deposited on an ITO/glass slide substrate. Then, the blend of poly(3-hexylthiophene-2,5-diyl) (P3HT) and phenyl-C61-butyric acid methyl ester (PCBM) with mass ratio of 1:0.8 dissolved in 1,2-dichlorobenzene was spin-coated on the TiO₂ layer. The grating pattern was created on the P3HT:PCBM layer by nanoimprinting technique using PDMS stamp. PDMS grating pattern template was created also by nanoimprinting using DVD-R grating template with the grating pitch of 740 nm. Poly(3,4ethylenedioxythiophene):poly(styrene sulfonate) (PEDOS:PSS) was then spin-coated on the patterned PHT:PCBM layer. Finally, Au was deposited on the PEDOT:PSS as a top electrode by vacuum evaporation technique. The fabricated device showed higher short-circuit photo-current as compared to standard flat solar cells. Transmitted-surface plasmon resonance (T-SPR) measurements showed that the surface plasmon excitation is one of the factors for an enhancement of the device performance. Furthermore, polarized UV-vis. absorption measurements exhibited that the P3HT molecules aligned in vertical direction (in-plane) to the grating groove direction after the nanoimprinting.

We have discussed about a novel technique of developing a nanostructured polypyrrole biosensor for measurement of very low concentrations of hydrogen peroxide in liquid media. The proposed fabrication method is very effective in growing a nanostructured conductive polymer layer on a planar conductive substrate. In addition enzyme loading was done under a high electric field of 1 kV/m. The developed sensor provides a linear range of 0-200 µmol/l of hydrogen peroxide and a measurement sensitivity of 6.5 Acm^-2 (mol/l)^-1.

Novel nematic liquid crystal (NLC) / nanofibers (NFs) composite device and its optical and electrical characteristics are presented. Parallel NLC/NFs composite devices are constructed by using indium tin oxide (ITO) glass with aligned PVA NFs on its surface. Those composite devices are then observed under cross-nicol condition to confirm the orientation of NLC molecules. Measurement of dielectric constant is carried out to estimate their electrical characteristics. Experiment result shows that the LC molecules are oriented along the direction of NFs and novel composite devices have shorter response time than those of pure NLC device. Further investigation on the decay waveform shows that, NLC/NFs composite has a decay time constant of dozens ms, much shorter than those of pure NLC.

An electric charge trapped in polymeric insulating material makes an ultra high electric field of 500 to 2000 kV/mm within 10 angstrom near trapped charge, that the electric field intensities have been calculated by the classical theory of Coulomb' law. This paper discusses the both of Fermi level and electrical potential distribution near trapped charge area by using the classical theory (Coulomb' law) and the quantum theory (electron wave function). It is found that the quantum theory is dominant within about 7.7 angstrom near trapped charge. Both of the classical and quantum theory should be considered a region 7.7 to 25 angstrom and there is ultra high electric field of 500 kV/mm to 2000 kV/mm in this region.

This paper presents an experimental study on temporal change of conduction current and space charge accumulation in a low density polyethylene (LDPE) under stepwisely increasing DC voltage. Steady currents under various applied fields from 0.1 to 1.9 MV/cm are simultaneously measured with the observation of space charge distributions in a 150-µm-thick LDPE between semiconductive (SC) rubber (anode) and evaporated-Al (cathode) system or evaporated-Al (anode) and evaporated-Al (cathode) system. It is known the relationship between the conduction current and applied voltage for solid dielectrics is classified in two models, ohmic-model (electrode limited model) and space-charge-limited current (SCLC) model (bulk-limited model). In general, the conduction model for solid dielectrics shifts from ohmic-model to SCLC-model with the increase in voltage. We confirm that the current characteristic of LDPE with Al(+)/Al(-) shifts from ohmic to SCLC at the critical applied field of 0.6 MV/cm. The current characteristics of LDPE with SC(+)/Al(-) under low applied fields below 0.4 MV/cm well agree with SCLC model because positive space charges injected from the SC anode are distributed in the bulk of LDPE. On the other hand, the current characteristics under higher applied fields indicate that the conduction mechanism is based on ohmic-model though a large number of positive space charges are accumulated in LDPE. The reason will be discussed on the bases of the simultaneous measurements of the external currents and the space charge distributions.

Dielectric properties were measured of epoxy composites filled with ZnO micro fillers in the range of 1 mHz-1 MHz of frequency at room temperature. In order to observe loss peaks in the composite samples, obtained data were transformed to “electric modulus”. We found two main dielectric relaxation peaks, which were fitted with Havriliak-Negami equations. Fine structure of the samples was investigated and the dispersion of the micro fillers in epoxy resin was found. The difference in 2nd relaxations for the samples might express the dispersion of micro fillers.

To investigate optimal concentration of O₃ and process time for sterilization of conidiospore of Colletotrichum sp., we examined sterilization by using CT (product of concentration and process time) as a sterilization index. The results showed that the usual CT was not be useful for interpreting sterilization.