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2,7-Difluo-carbazole and 2,4,5,7-tetrafluoro-carbazole were synthesized as new building blocks of wide-energy-gap host material for phosphorescent organic light-emitting diodes (PHOLEDs). These fluorinated positions in the carbazole ring were determined on the basis of density functional theory calculation results. Spectroscopic analyses supported the hypothesis that poly(N-vinyl-2,7-difluoro-carbazole) (2,7-F-PVK) with the fluorinated pendant group possessed a wide energy gap, leading to the exciton energy confinement on the blue phosphorescent dopant as well as nonsubstituted poly(N-vinyl-carbazole) (PVK). 2,7-F-PVK was used in solution-processed blue PHOLED to achieve 27 cd/A at 760 cd/m2, which is 1.8 times higher than that of nonsubstituted PVK. We assumed that the replacement of nonsubstituted PVK with 2,7-F-PVK improved the charge balance in the emission layer, while keeping the exciton confinement effect. The fluorination of the carbazole ring is a useful molecular design strategy for wide-energy-...

A large shift of the localized surface plasmon resonance (LSPR) spectrum of gold nanoparticles was attained by electrochemical oxidation of the nanoparticle surface. This oxidation occurred in the cell, which consisted of a pair of indium tin oxide (ITO) electrodes and water medium between the electrodes. On one side of the ITO electrode, the gold nanoparticles were adsorbed. With the application of a voltage of 5 V to the cell, a spectrum shift as large as 68 nm was obtained. Though the spectrum shift has already been observed by changing liquid crystal (LC) orientation surrounding gold nanoparticles, the size of the shift was not large (11 nm). That was because the variation of the effective refractive index of LC was rather small. Our large shift due to electrochemical oxidation resulted from the large refractive index of Au−O. The electrochemical oxidation was confirmed by XPS analysis of the gold nanoparticles with the LSPR spectrum shift. Other possible mechanisms of the shift such as charge localiz...

A flat panel image sensor with a simple structure, which contains only one a-Si:H TFT and a storage capacitor in each pixel, has been proposed. Instead of utilizing external voltage supply, a feedthrough voltage caused by parasitic capacitance of TFT was applied to extract the photogenerated charges in a-Si:H thin film. Decrease of feedthrough voltage owing to the photoleakage current during the transient time caused by gate pulse distortion was estimated to be less than 10%. A 3.8-inch prototype image sensor was fabricated, and sensor operation with 3-4bit still and motion image was successfully obtained. The possibility of high-aperture-ratio LCD with embedded image sensor has been shown.

We have developed a micro local heating device for bio applications using micro-electro-mechanical systems (MEMS) technology. The device has a two-dimensional microdish array, which contains a series of diodes. The microdish array is fabricated by means of a combination of complementary metal–oxide–semiconductor (CMOS) technology and MEMS post-processing. The microdish array has a miniature cavity for thermal separation from substrate. These microdish arrays can be generated by a large forward current based on Joule heating. In this paper, we describe the direct heating of the whole microdish array and just an arbitrary portion of the microdish consisting of the device by Joule heating. In the localized selective heating, the highest temperature, 62.6 °C, from all the dishes was confirmed. More than twice the heat effect was achieved in heating an arbitrary portion compared with heating the whole microdish.

We have developed an electrochemical reaction display (ECRD) that can be operated in dual reflective and emissive modes in an entire pixel area of a single device. The ECRD utilizes electrochromic (EC) and electrogenerated chemiluminescence (ECL) reactions. These two electrochemical reactions can be controlled independently by adding a luminescent molecule to a liquid electrolyte of an EC cell with three electrodes. In the reflective mode, the ECRD cell exhibits high reflectance (47%) and high contrast ratio (6:1). In the emissive mode, the cell can show luminescent moving images because of the fast response time (10 ms).

Non-piezoelectric inkjet printing methods, namely, ultrasonic inkjet printing and electrostatic inkjet printing have been used for fabricating an all-solution-processed organic thin- film transistor. Silver nanoparticle ink is patterned to form source/drain electrodes using the electrostatic inkjet method and high-viscosity poly(3,4-ethylenedioxythiophene) doped poly (styrene sulfonate) (PEDOT:PSS) was patterned as a gate electrode using ultrasonic inkjet printing. Polymer insulator and polymer semiconductor are spin-coated as a gate dielectric layer and a semiconductor layer, respectively. This is the first fabrication of all-solution-processed organic transistor using non-piezoelectric inkjet printing.

Electrical characteristics of n-type diamond Schottky diodes and metal/diamond interfaces have been systematically investigated for phosphorus (P)-doped homoepitaxial diamond layers. The current-voltage (I-V) characteristics of the Ni/n-type diamond Schottky diode show excellent rectification properties from 297 K to 773 K. The ideality factor and the rectification ratio were 1.0 and ∼10 6 at +10 V at 573 K, respectively. The rectifying properties deteriorated with increasing P concentration in the diamond layers. Temperature-dependent capacitance-frequency (C-f) and conductance-frequency (G-f) measurements on the Schottky diodes have shown that the capacitance is reduced at high frequency due to the inability of deep centers to maintain an equilibrium ionization state under a high-frequency modulation. C- V measurements deduced that the P electrical activity (the ratio of the net donor concentration to the P concentration) was nearly 1 from low concentration (1.6 x 10 16 cm -3 ) to high concentration (2.7 x 10 18 cm -3 ) of P. The Schottky barrier height was found to be almost constant at ∼4.3 eV independent of the metal work function (Ni, Pt, Al and Ti).

The elimination of conventional peripheral LSI (large-scale integration) drivers is considered essential to the development of future low-cost, energy-efficient, lightweight, and thin displays. System-on-glass (SOG) displays are a type of display with various functional circuits integrated on a glass substrate. Low-temperature polycrystalline silicon (LTPS) thin-film transistors (TFTs) make the integration of circuits possible because they can be assembled into complex, high-current driver circuits. Furthermore, LTPS TFTs are attracting attention for driving organic light-emitting devices (OLEDs). This article introduces present and future LTPS TFT technologies for SOG displays.

Excimer laser anneal (ELA) has allowed the production of large-area poly-Si thin-film transistor liquid crystal displays (TFT-LCDs) on a glass substrate. The state of the art of large-area low-temperature TFT-LCDs is reported in this paper. High-performance poly-Si TFTs are expected to achieve various applications such as system-on-glass where various functions are added on to the display. Possible applications and future trends are discussed together with the technologies required to achieve this goal.

A cold cathode fluorescent lamp (CCFL) is a gas discharge light source widely used for liquid crystal display (LCD) backlighting. We proposed applying diamond as a new cathode material to reduce the power consumption of the CCFL. In this work, we show stable and low (less than 50% of metal) cathode-fall voltage for a glass discharge tube.

The characteristics of hydrogenated amorphous silicon (a‐Si:H) thin‐film transistors are investigated as a function of the overlap of the source electrode Lovs on top of the passivation layer. The drain current is reduced by Lovs and the effect is dependent on drain voltage and a‐Si:H layer thickness. The effect is enhanced at high drain voltage and at thin a‐Si:H layer thickness. At high drain voltage, field‐effect mobility and threshold voltage decrease as Lovs increases. Numerical calculation of carrier concentration in a‐Si:H layer showed that the carrier is depleted under Lovs and that the effective channel length is shortened by the size of Lovs. The nonlinear resistance formed by Lovs is discussed in terms of drain voltage and a‐Si:H layer thickness.

Silicon nitride (SiNx) films of various quality were deposited on the back‐side of a‐Si:H thin film transistors (TFTs) as a passivation layer. Although the films were not deposited directly on the channel region, the N/Si ratio of the film affected the TFT performance. It changed the threshold voltage and the subthreshold slope. In the linear region, the effect of the passivation layer was explained by assuming fixed charges in the nitride layer. Furthermore, the current‐voltage characteristics in the saturation region were explained by a parasitic TFT model. It was determined that a nitrogen rich passivation film is preferrable for liquid crystal displays.

Host materials for phosphorescence organic light-emitting diodes (OLEDs) are required to have wide energy gap to prevent back energy transfer and confine triplet exciton on guest molecules. Carbazole (Cz) has been widely used as a building block for host materials because of its relatively high energy gap. We found that the energy gap of Cz can be widened by fluorination at specific positions. A characteristic of the energy gap widening by fluorination is its controllability by the number and position of fluorine substituents. We synthesized 2,7-difluorocarbazole (F-Cz) and estimated the energy gap of Cz and F-Cz from absorption spectra to be 3.59 eV and 3.71 eV, respectively. To confirm the wide-gap effect of F-Cz on OLED device, we synthesized a solution-processable polymer host, poly(N-vinyl-2,7-difluorocarbazole) (F-PVK), which has F-Cz as pendant groups, and compared it with poly(N-vinylcarbazole) (PVK). The OLED devices investigated consisted of an ITO/PEDOT:PSS/EML/CsF/Al multilayered structure. The poly(3,4-ethylenedioxythiophene) poly(styrenesulfonate) (PEDOT:PSS) layer was spin-coated onto an indium tin oxide (ITO) coated glass substrate. Subsequently, the emission layer (EML) composed of PVK or F-PVK, 1,3-bis[(4-tertbutylphenyl)-1,3,4-oxidiazolyl]phenylene (OXD-7), and a blue phosphorescent dopant, iridium(III)bis [(4,6-difluorophenyl)-pyridinato-N,C2'] picolinate (FIrpic) was spin-coated, and the CsF and Al layers were vapor-deposited. The OLED device with F-PVK showed 1.8 times higher maximum current efficiency (27 cd/A) than that with PVK (15 cd/A). The improved efficiency of F-PVK device can be rationalized by the enhanced triplet confinement effect of polymer host composed of fluorinated carbazole.

Fluorinated carbazoles as host materials have been investigated for highly efficient organic light emitting diodes (OLEDs). By molecular orbital calculations, we found that fluorinations at position 2, 4, 5 and 7 of carbazole ring were effective for widening HOMO-LUMO energy gap. The energy gaps of our synthesized 2,7-difluorocarbazole (F2-Cz) and 2,4,5,7-tetrafluorocarbazole (F4-Cz), were estimated to be 3.71 eV and 3.87 eV by the absorption spectra, respectively. These energy gaps were higher than that of the non-substituted carbazole (Cz, 3.59 eV). We synthesized poly(N-vinyl-2,7-difluorocarbazole) (F2-PVK) and poly(N-vinyl-2,4,5,7-tetrafluorocarbazole) (F4-PVK) as solution processable polymer host materials. However, the F4-PVK was found to be an unsolved polymer. The F2-PVK could be compared with non substituted poly(N-vinylcarbazole) (PVK) in OLEDs. The emission layer (EML) contained iridium(III) bis [(4,6-di-fluorophenyl)-pyridinato-N,C2′] picolinate (FIrpic) as a blue phosphorescent dopant, and iridium(III) bis [2-(9,9-dihexylfluorenyl)-1-pyridine] acetylacetonate as a yellow dopant. The white OLED with the F2-PVK showed 1.4 times higher luminous current efficiency (24 cd/A) than the PVK (17 cd/A). These data show that the excitation energy is confined on dopants by using fluorinated polymer host material with higher T1 corresponding to wider HOMO-LUMO energy gap.

Large shift of localized surface plasmon resonance (LSPR) spectrum of gold nanoparticles was attained by electrochemical oxidation of the nanoparticle surface. This oxidation occurred in a cell consisting of a pair of indium tin oxide (ITO) electrodes with water medium between the electrodes. On one side of the ITO electrode, the gold nanoparticles were adsorbed. The LSPR spectrum was moved consecutively to the red by increasing the applied positive voltage. By the application of 5 V to the cell, the spectrum shift as large as 55 nm was obtained. Though the spectrum shift has already been observed by changing liquid crystal (LC) orientation surrounding gold nanoparticles, the amount of the shift was not large (11 nm). That was because the variation of the effective refractive index of LC was rather small. Our large shift due to electrochemical oxidation resulted from the large refractive index of Au-O. The upper limit of the LSPR spectrum shift by our method is estimated to be 138 nm.

This article consists of a collection of slides from the author's conference presentation on micro manipulator arrays for nano-bioelectronic applications. Some of the specific topics discussed include: the special features of a micro manipulator array using a novel MEMS-based structures; the demonstration of direct physical control of the interaction between yeast cells and silica particles in liquid for the first time; the adsorption of the particle to the cell was demonstrated using vibrational energy; and Joule heating energy according to external excitation. These results of these tests show a potential impact in medical fields such as physical antibiotics and cell treatments and next generation bio-electronics schemes.

In this paper we proposed a method by which nanoparticles can be selectively injected based on mechanical vibrations, thermal heating, and electromagnetic waves. We have developed a nanoparticle manipulator using a MEMS based structure. We also demonstrated direct physical control of the interaction between yeast cells and nanoparticles in liquid for the first time. In this research, our aim is to develop human clinical devices designed to obtain personal data in order to select the suitable types of nanoparticles for tailor-made medical treatments. These results can have a potential impact in medical fields such as physical antibiotics and cell treatments

We have made a prototype of flexible display system integrated with bend-input function. It consists of flexible display, flexible backlight unit with bending sensor, and MPU connected to PC. Zooming in/out in Google Earth and paging up/down in PDF files have been successfully done by bending the flexible display.

The gate/source overlap distance (ΔLs) is an important factor in fabricating self-aligned TFT with passivating layer. Six types of TFT were fabricated using thin intrinsic a-Si layers such as 20 nm,50 nm and 100 nm and a n+:a-Si or a n+:μc-Si were used as the contact layer. The least required gate/source overlap distance, ΔLsC is the critical overlap where the TFT performance is not limited by the contact. This ΔLsc was determined experimentally. ΔLsC was found to be significantly affected by the intrinsic a-Si layer thickness and the ΔLsc can be small by depositing a thin intrinsic layer. The intrinsic layer thickness dependence of ΔLsC in the linear region can be explained from a existing model. However, the behavior in the saturation region suggests the need of another model, which will be discussed here. The variation of n'contact layer shown to have a small effect on ΔLsc. In order to determine appropriate ΔLs for self-alignment TFT, the magnitude of field effect mobility, threshold voltage and drain current as well as ΔLscmust be considered.

— A 9-in. full-color polymer-stabilized OCB TFT-LCD with stable bend alignment in the absence of an electric field was developed. The condition of the polymer stabilization, the characteristics of UV-curable monomers, and their influence on the configurations of the polymer network in the cell were studied. Possible models of the configuration were proposed and their relationship to the electro-optical properties was analyzed using a novel simulation method considering the distribution of anchoring effects from both alignment surfaces and the polymer network. It was suggested that a good performance such as high contrast ratio and fast response could be expected in the polymer network originating from newly developed monomers composed of multifunctional LC acrylates due to a relatively weak-anchoring effect and presumably its localization near the alignment surfaces. By using the newly developed monomers under the optimized polymer-stabilizing process, a high contrast ratio of 250:1 and fast response nearly equal to that of a conventional OCB cell were achieved.

Based on molecular orbital calculation, solution processable fluorinated polyvinylcarbazole (poly (N-vinyl 2,7- difluorocarbazole), (F-PVK)) is synthesized as host material for blue electrophosphorescent organic light-emitting diodes (OLEDs). F-PVK successfully confined triplet excitons to the guest phosphorescent material, iridium(III) bis[(4,6- difluorophenyl)-pyridinato-N,C2′]picolinate (FIrpic). To the authors' knowledge, it showed the highest up-to-date solution- processed blue polymer OLED efficiency of 27 cd/A at 760 cd/m2.

To improve the efficiency of bend transition in OCB, its anisotropy was analyzed. The transition antiparallel (opposite) to the rubbing direction was significantly fast and this anisotropy remained at low temperatures. We propose two effects of LC shear flow on the anisotropy. Based on a pixel design that takes the anisotropy into consideration, 40% reduction of the initialization voltage in a 3-inch TFT-LCD has been achieved.

Fabrication of electronic devices by printing technique is attracting interest in the expectation of lowering production cost. There is an ongoing work using various printing methods. This paper outlines some of the important aspect of printing in terms of fabricating thin film transistor (TFT) arrays. Appropriate combination of inkjet head and the ink material must be considered. Non-piezoelectric inkjet printing methods, such as ultrasonic inkjet printing and electrostatic inkjet printing are also introduced for fabricating all-solution-processed organic thin-film transistor.

— An ink-jet-printing method applied to the microdeposition of high-viscosity resin, including optimization of phosphor dispersion for light-emitting-diode (LED) packaging was examined for the first time. An ultrasonic ink-jet-printing method was used, in which ink droplets are ejected by a focused ultrasonic beam from a nozzle-less printhead. To fabricate white LEDs, high-viscosity phosphor-dispersed resin was deposited to form an encapsulant dome. Two types of methods to control phosphor sedimentation for color uniformity were examined; one is heating the lead frame during the resin deposition, and the other is hydrophobic surface treatment of the lead frame base enabling the fabrication of a small encapsulant dome. For light direction control, a silicone micro lens was deposited on an encapsulant dome using the ink-jet method. The results show that ultrasonic ink-jet printing is an applicable technique to optimize and modify on-demand optical characteristics of LED devices.

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A novel formation process for TFT using our proposed novel selective transfer technique, which enables low cost TFT fabrication on a large and flexible substrate, is proposed. This technique is used to fabricate a 3.2-inch LCD Panel using amorphous silicon TFT transferred on glass substrate for the first time.

Resist pattern transformation by backside exposure, which is a key process for a self-alignment technique is investigated. The light intensity and a-Si:H thickness markedly affect the pattern transformation, while the effect of gate insulator thickness is small. Numerical simulations based on Fresnel diffraction showed fairly good agreement with the experimental results.