Suguru Mototani

Performance of Organic Field-Effect Transistors with Poly(3-hexylthiophene) as the Semiconductor Layer and Poly(4-vinylphenol) Thin Film Untreated and Treated by Hexamethyldisilazane as the Gate Insulator

The relationship between the carrier mobility and the structure/morphology of polymer semiconductor molecules on a substrate remains a very important issue in organic electronics. In this paper, the relationship between the crystallinity of drop-cast regioregular poly(3-hexylthiophene-2,5-diyl) (RR-P3HT) thin films and polymer substrates was discussed by using heat-crosslinkable poly(4-vinylphenol) (PVP) as the gate insulator in organic field-effect transistors (OFETs). The effect of a self-assembled monolayer (SAM) of 1,1,1,3,3,3-hexamethyldisilazane (HMDS) on crosslinked PVP was also examined and the performance of the OFET was investigated. Results show that not only the orientation and crystallinity of the polymer semiconductor are very important in determining the OFET performance, but also the gate dielectric properties, surface roughness, and the interface properties between the gate and semiconductor layers are important factors.

Third-Harmonic Generation of Regioregular Poly(3-hexylthiophene) Thin Films Prepared Using Two Solution Methods

In this paper, we report on the third-order nonlinear optical properties of poly(3-hexylthiophene) (P3HT) thin films prepared using solution methods. The third-order optical susceptibilities χ(3)(-3ω;ω,ω,ω) of P3HT thin films spin-coated and drop-cast on quartz glass substrates were estimated from optical third harmonics measured using the Maker-fringe method. The orientation, alignment, and crystallinity of the P3HT thin films obtained were evaluated using atomic force microscopy (AFM), X-ray diffraction (XRD) analysis, and UV–visible absorption spectra. The maximum nonlinear optical susceptibility χ(3) (NLOS), as estimated from the drop-cast film, was 1.55×10-8 esu, which was higher than that of a spin-coated film by one order. The enhancement of χ(3) is associated with the orientation and crystallinity of the P3HT molecule on the substrate.

Optical bistability of terthiophene/polymethylmethacrylate composite film

In our previous data, following organic gas treatment in 1,2-Dichloroethane vapor, the third order nonlinear susceptibility of a tertiary-butyl vanadylphthalocyanine ((t-Bu)1.45VOPc)/polymethylmethacrylate (PMMA) composite film was observed to increase markedly, because the phase morphology of the composite film changed from Phase I to II. Therefore, the third order nonlinear optical property of the quasi-waveguide, comprised of composite film, was stronger than that before organic gas treatment. When irradiating the quasi-waveguide treated organic gas for 25 hrs with input laser power intensity, the output power had optical bistability. The optical bistability also displayed excellent stability and effective reproducibility. However, in terms of the input laser power intensity dependences of optical bistability, the switching on-off position shifted with the increase in input laser power intensity. In this study, we adopted a terthiophene(3T)/PMMA and poly(3-hexylthiophene)[P3HT]/PMMA composite films, possessing strong third-order optical nonlinearity, to decrease the change in the on-off position depending on the input laser power intensity. The optical bistability of the optical devices, fabricated using a prism, 3T/PMMA or P3HT/PMMA composite films were investigated. The shift in the on-off position in optical bistability characteristics caused by the refractive index change in the thermal effect was improved by the use of the terthiophene (3T)/PMMA or P3HT/PMMA composite films.

Extraction of human action elements with transition network of partial time series data modeled by Hidden Markov Model

The authors have researched on a method of human action modeling to realize systems such as to support human human operations or watch persons to prevent various kinds of accidents. In order to recognize or support various kinds of human actions, a certain human action model is necessary in these systems. Therefore, we have proposed a modeling method of human actions, which is extracted statistically from enormous data acquired from various kinds of sensors by long-term observation of human actions and situations around persons. However, human action elements composing a model should have been extracted heuristically by a designer. In this paper, an extraction method of human action elements is proposed in order to extract frequent human action elements automatically from acquired data. In the proposed method, a series of acquired time series data is divided into short partial ones, which are modeled by Hidden Markov Models(HMM). Then, the transition network of generated HMMs is constructed based on the likelihood between the original data and each HMM. In the obtained network, a transition sequence with the only one edge is regarded as a frequent human action element. Extraction results with artificial and actual human action data are shown in this paper in order to verify the usefulness of the proposed method.

An impedance voltage compensation and vibration voltage suppression control by using inexact differential in a single-phase PWM inverter

We propose an impedance voltage drop compensation method and a vibration voltage suppression control method by using feed-forward control. The filter L voltage is estimated from an inverter output current and the filter C current is estimated from by using inexact differential calculation, respectively. The design method for the proposed control is shown. In the case of linear-load and non-linear-load, we examine the proposed method by simulations and experiments.

A DC voltage estimation at the maximum power point of a series parallel connection PV system with partial shade

This paper describes a DC voltage estimation at the maximum power point of a series parallel connection photovoltaic (PV) system with partial shade. The PV system converts sunlight into electric power. The IV (current-voltage) curve of the solar cell describes its energy conversion capability at the existing conditions of light level. The PV (power-voltage) curve which determines the maximum output power is computed from the IV curve. It is necessary to operate the solar cell at the voltage which provides the maximum power. The maximum power point tracking (MPPT) control using hill-climbing method is widely used. However, the output power from the PV system is reduced if weather condition changes and the area of the receiving portion of the PV panel decreases. In these cases, IV characteristics of the PV panel also changes. There is a possibility that the maximum power point cannot be captured by the conventional MPPT control in case that the maximum power would be two or more. We propose a method for the estimation of the DC voltage at the maximum power point by using the equivalent circuit of the solar cell.

Levitation energy of piezoelectric actuator using a levitation mechanism

In this research, we focused on the energy consumed in the levitation mechanism used in an inchworm-type microactuator when the mechanism is levitated. We use a power meter for the measurement of the energy required for levitation. We estimate the levitation height by comparing the levitation height measured by a displacement sensor and the power consumption measured by a power meter. The levitation height measured with the displacement sensor shows the similar trend obtained with the power used in the levitation mechanism. We are studying a piezoelectric actuator used in a levitation mechanism. The levitation mechanism levitates using a squeeze effect caused by the vertical vibration of the piezoelectric element. Frictional force control is realized by using levitation mechanisms, and the microactuator moves by the principle of inchworm. We usually measure the displacement of the levitation mechanisms by the use of a displacement sensor. However, the measurement of the vertical direction is difficult because there are a number of limitations. Therefore, a measurement method without displacement sensors in the vertical direction is required. The estimation method proposed in this paper can extend the working range of the microactuators. The energy consumed in the microactuator includes the information of the actuator. We measure the energy and the state simultaneously, and levitation height used for levitation is estimated. The measured and estimated levitation height as a function of the operation frequency is also discussed.

Novel nonlinear optical material with poly(3-hexylthiophene) thin film prepared on quartz glass surface modified by self-assembled monolayer

The third-order nonlinear optical properties of regioregular poly(3-hexylthiophene) (RR-P3HT) thin films prepared on fused glass substrate were evaluated. The surface modification by hexamethyldisilazane (HMDS) and octadecyltrichlorosilane (ODTS) was performed on the glass substrate to form self-assembled monolayer (SAM) layers. The formation of SAM layers on the glass substrate increase the contact angle of the solution and the optical property of the RR-P3HT thin films is enhanced due to the excellent orientation and alignment of the thin film. The π-conjugated macromolecule thin films can be prepared by spin-coating and drop-casting methods and the structure and orientation alignment of thin films can be controlled by the solution processing and deposition techniques. The nonlinear optical property, third-harmonic generation of RR-P3HT thin films has been evaluated by Maker-fringe method. The third-order nonlinear optical susceptibilities χ(3) (-3ω; ω, ω, ω) of drop-cast RR-P3HT thin films on quartz glass substrate were estimated from optical third-harmonics (TH) intensity measurement. An Nd:YAG laser with a wavelength of 1064 nm, pulse width of 5 ns and a repetition frequency of 10 Hz was used to evaluate the TH intensity. The effect of surface modification of quartz glass substrate by HMDS and ODTS on the RR-P3HT film structure was also investigated. The orientation alignment and crystallinity of the RR-P3HT thin films were evaluated using X-ray diffraction (XRD) and UV-vis absorption spectra. The UV-vis and XRD profile reveals the better orientation and crystallinity of the RR-P3HT thin film after surface modification by HMDS and ODTS. Moreover the incident angle dependences of third harmonic (TH) intensity was measured and the TH intensity of RR-P3HT thin film prepared on glass substrate with SAM layer was found to higher than that of non-treated substrate. The SAM layers significantly enhances the optical property of the material and the third-order nonlinear optical susceptibility (χ(3)) of RR-P3HT thin films on quartz glass surface modified by ODTS is 1.90 × 10-8 esu. The third-order nonlinear optical susceptibility (χ(3)) of RR-P3HT thin film was found to higher than poly(p-phenylenevinylene) (PPV).

Optical bistability of waveguide consisting of poly(3-hexylthiophene)/polymethylmethacrylate composite film

In the optical materials, the remarkable change of refractive index due to optical intensity is important for making photo-devices such as optical switching, memory and logic circuits. The optical waveguide consisted of poly (3-hexylthiophene)/polymethylmethacrylate (P3HT/PMMA) composite film and a prism was fabricated to find out its optical bistable characteristics. The refractive index of P3HT/PMMA composite film measured by ellipsometry was 1.48. Moreover, the refractive indexes of the atmosphere and the prism were 1.00 and 1.52 respectively. Therefore, the fabricated waveguide satisfied the condition of the quasi-waveguide. For improving the nonlinear optical characteristic of the composite film, P3HT/PMMA composite film was exposed to organic gas for 25 hrs. As the laser light source, Nd:YAG laser (wavelength: 1064 nm, pulse width: 5 ns, repetition frequency: 10 Hz) was adopted for optical bistability and third-harmonic intensity measurement. The input light intensity dependences of the optical bistable characteristics of the quasi-waveguide consisting of the P3HT/PMMA composite thin film, which was exposed to organic gas for 25 hrs were investigated. The measured optical bistability displaced excellent stability and hysteresis characteristics. It suggests that the composite film exposed to organic gas has larger grain size, better molecular orientation, homogeneous bulk and smooth surface than that of before organic gas treatment.

Thickness dependence of morphology and third-order nonlinear optical characteristics of metal-phthalocyanine thin films prepared with different thicknesses on KBr substrate

The third-order nonlinearity of nonlinear optical materials is of great importance in achieving all-optical switching. However, the relationship between the morphology and third-order nonlinear optical characteristics of metal-phthalocyanine thin film is unclear. In this paper, the thickness dependence of the morphologies and the nonlinear optical properties of titanylphthalocyanine (TiOPc) and vanadyl-phthalocyanine (VOPc) thin films prepared on a KBr substrate are investigated by using UV/Vis spectra, X-ray diffraction (XRD), and third-order harmonics (TH) and second-order harmonics (SH) detected using the Maker fringe method. TiOPc and VOPc thin films having different thicknesses were prepared on a KBr substrate using a molecular beam epitaxy (MBE) method. From the Vis/UV spectra of VOPc thin films fabricated on KBr substrate, the VOPc thin film epitaxially grows until the thickness of 90nm and VOPc thin films that are thicker than 90 nm change to a pseudomorphic layer. In the incident angle dependence of TH intensity, the maximum TH intensity of the pseudomorphic layers is not proportional to the square of film thickness. This indicates that defects inside the pseudomorphic layers are closely related to the maximum TH intensity not being proportional to the square of film thickness. These defects may be due to the misfit between the VOPc and TiOPc molecules and the KBr substrate. On the other hand, within the thickness of the TiOPc thin films fabricated on KBr substrate, the TiOPc thin films mainly grow with epitaxy. However, the maximum TH intensity measured with the TiOPc thin film is lower than that of the VOPc thin film. This is related to the molecular packing density of VOPc thin film being larger than that of TiOPc thin film.