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In this study, the Nd x Fe1− x N y materials are applied for the magnetic core of the series resonance circuit of GaN wireless power transmission (WPT) for the first time. At over 10 MHz, the inductance of the fabricated Nd2Fe17N3 coil is stable at $1.15~\mu \text{H}$ and the effective magnetic permeability of the Nd2Fe17N3 is estimated to be 2.6. At the same inductance, the number of turns of the Nd2Fe17N3 coil can be decreased as compared with that of the air-core coil, and the coil size can be reduced by 0.7 times by using the Nd2Fe17N3 material. At the 13.56 MHz GaN-WPT operation, the successful WPT waveforms can be obtained, and the drastic reduction of the energy loss at the coil is achieved due to the low imaginary part of the magnetic permeability. The Nd-Fe-N materials are considered indispensable to GaN high-frequency switching circuits.

Cooling heat loss is one of the most dominant losses among the various engine losses to be reduced. Although many attempts to reduce it by insulating the combustion chamber wall have been carried out, most of them have not been successful. Charge air heating by the constantly high temperature insulating wall is a significant issue, because it deteriorates charging efficiency, increases the emissions of soot and NOx in diesel engines, and promotes the knock occurrence tendency in gasoline engines. A new concept heat insulation methodology which can reduce cooling heat loss without heating the charging air has been developed. Surface temperature of insulation coating on the combustion chamber wall changes rapidly, according to the quickly changing in-cylinder gas temperature in each engine stroke. During the compression and expansion stroke, the surface temperature of the insulation coating goes up rapidly, and consequently, the heat transfer becomes lower by the reduced temperature difference between the surface and the gas. During the intake stroke, the surface temperature goes down rapidly, and it prevents intake air heating from the wall. To realize the above-mentioned functionality, a thin coating layer with low thermal conductivity and low heat capacity was developed. It was applied on the pistons of diesel engines, and showed improvement in thermal efficiency. It also showed a reduction of unburnt fuel emission in low temperature engine starting condition. The energy balance analysis showed reduction of cooling heat loss and, on the contrary, increase in the brake power and the exhaust loss.

We propose a promising preparation technique to construct optically high-quality Langmuir-Blodgett (LB) films of lead bromide-based layered perovskites having an organic-inorganic quantum-well structure called "squeezed-out technique." Using this technique, we successfully prepared PbBr-based layered perovskite LB films whose average roughness is small enough to apply them for cavity polariton devices. The small roughness reveals that one can prepare microcavities having a high quality factor by using the technique. In addition, optical simulation of a cavity using the LB film demonstrated that the cavity polariton device has a large Rabi splitting of 116 meV, suggesting a stable polariton formation in the cavity even at room temperature.

An accelerated test method for evaluating the long-term lifetime and color shift of white OLED panels based on device-degradation models was proposed. We successfully estimated the lifetime and color shift of white OLED panels at standard drive conditions with a short test period.

The dynamic characteristics of GaN-based vertical-cavity surface-emitting laser (VCSEL) with an AlInN/GaN semiconductor distributed Bragg reflector has been reported for the first time. The max dynamic lasing frequency of 1.1 GHz with a wavelength of 415 nm and a threshold current of 7 mA has been demonstrated. Moreover, at the pulse lasing operation, both the steep lasing waveforms and the tailing spontaneous emission waveforms were observed in driven with the square pulse waveforms. The dynamic lasing frequency driven by the sine waveform seems to be related to this steep lasing waveform at the square pulse operation. During these dynamic measurements, the lasing characteristics of the VCSEL were gradually degraded, and the lasing power is decreased by −7 dB at the same bias condition after several hours.

Non-destructive analyses are conducted on the intrinsic degradation of organic light-emitting diodes (OLEDs). After longterm operation, sum-frequency spectroscopy reveals changes in the molecular orientation. Furthermore, change in the mobility of the OLEDs can be evaluated from impedance spectroscopy. Carrier trap behavior is also investigated via thermally stimulated current spectroscopy.

In this study, the Nd–Fe–N materials are employed as an electromagnetic shield, for the first time, for the resonance coil in the 13.56-MHz-GaN wireless power transmission circuit. The Nd–Fe–N materials are introduced into the air-core resonance coil as the cap of the edges or the core. By using Nd–Fe–N, the radiated emission from the resonance coil is reduced because the electromagnetic field distribution is shrunk due to the effect of not the imaginary part but the real part of the permeability. When the spectrum of the magnetic field of the resonance coil is measured at the frequency from 30 MHz to 800 MHz, the intensity of the higher harmonics radiated emission is restricted by Nd–Fe–N in all of the frequency ranges. In particular, the Nd–Fe–N capped air-core coil shows the superior characteristics in both the shielding effect and the power loss. In addition, by numerical calculation, it is found that the effect of the electromagnetic shield will be enhanced by increasing the real part of the permeability by optimizing the Nd–Fe–N material fabrication.In this study, the Nd–Fe–N materials are employed as an electromagnetic shield, for the first time, for the resonance coil in the 13.56-MHz-GaN wireless power transmission circuit. The Nd–Fe–N materials are introduced into the air-core resonance coil as the cap of the edges or the core. By using Nd–Fe–N, the radiated emission from the resonance coil is reduced because the electromagnetic field distribution is shrunk due to the effect of not the imaginary part but the real part of the permeability. When the spectrum of the magnetic field of the resonance coil is measured at the frequency from 30 MHz to 800 MHz, the intensity of the higher harmonics radiated emission is restricted by Nd–Fe–N in all of the frequency ranges. In particular, the Nd–Fe–N capped air-core coil shows the superior characteristics in both the shielding effect and the power loss. In addition, by numerical calculation, it is found that the effect of the electromagnetic shield will be enhanced by increasing the real part of the permeabi...

Sum frequency generation (SFG) spectroscopy has been used to study the operational degradation of 4, 4′-bis[N-(1-naphthyl)-N-phenylamino]-biphenyl (α-NPD)/tris(8-hydroxylquinoline) aluminum (Alq3) organic light-emitting diodes (OLEDs). A reduction in the SFG peak strengths of Alq3 was found in aged OLEDs, indicating that the permanent dipole orientation in the Alq3 layer was randomized as a result of long-term continuous operation. In contrast, the SFG signals derived from the α-NPD in aged samples were enhanced as compared to those of pristine OLEDs, and it can be attributed to an increase of the internal electric field near the interface by the long-term operation.

Silicon carbide (SiC) and gallium nitride (GaN) devices have been found to withstand high voltages without showing degradation and can be switched at high frequencies, making them attractive for high-power drives. Although Sic/GaN devices can be operated at high temperature and high frequencies, it is important to develop gate-drive circuits to efficiently turn on and off these devices at high speeds. This paper proposes a resonant gate-drive circuit that aims at reducing the power loss associated with high-frequency switching of power insulated gate bipolar transistors/metal–oxide–semiconductor field-effect transistors. The main thrust of the circuit is its application to the motor-drive industry. The proposed circuit is compared with traditional gate-drive circuits from the points of view of power consumption and switching speed. Experimental results are given to illustrate the concept. Test results show that the power consumption using the proposed circuit reduces by a factor of greater than 5 compared with a traditional gate-drive circuit.

Organic light emitting diodes are extremely sensitive to dopant concentrations in emitting layers. We developed a sensor that could simultaneously monitor the composition and thickness of co-deposited films. This sensor enables more precise control of the composition of the emitting layers compared to quartz crystal oscillator thickness monitors.

We previously reported that dipoles on the surface of the gate insulator layer in organic transistors cause time decay of the drain current on time scales of less than 0.1 s from the application of the gate voltage. In this study, we investigated the relationship between the time decay and magnitude of the gate voltage. We found that this time decay can be attributed to threshold voltage shifts unaccompanied by mobility changes. When the insulator surface has dipoles that can move somewhat, the threshold voltage shift has two components: one with a time scale of approximately 0.1 s and the other with a time scale of tens of minutes.

Diode rectifiers with large dc-bus capacitors, used in the front ends of variable-frequency drives (VFDs) and other ac-to-dc converters, draw discontinuous current from the power system, resulting in current distortion and, hence, voltage distortion. Typically, the power system can handle current distortion without showing signs of voltage distortion. However, when the majority of the load on a distribution feeder is made up of VFDs, current distortion becomes an important issue since it can cause voltage distortion. Multipulse techniques to reduce input current harmonics are popular because they do not interfere with the existing power system either from higher conducted electromagnetic interference, when active techniques are used, or from possible resonance, when capacitor-based filters are employed. In this paper, a new 18-pulse topology is proposed that has two six-pulse rectifiers powered via a phase-shifting isolation transformer, while the third six-pulse rectifier is fed directly from the ac source via a matching inductor. This idea relies on harmonic current cancellation strategy rather than flux cancellation method and results in lower overall harmonics. It is also seen to be smaller in size and weight and lower in cost compared to an isolation transformer. Experimental results are given to validate the concept.

Variable-frequency drives (VFDs) with diode front-end rectifiers are typically equipped with a resistor-contactor arrangement to limit the inrush current into the dc-bus capacitors, thereby providing a means for soft charging the dc-bus capacitors. Because of the mechanical nature of the magnetic contactor typically used in VFDs, there exists a concern for fatigue. In addition, during a brownout condition, typically, the contactor remains closed, and when the voltage recovers, the ensuing transient is often large enough to possibly cause unfavorable influence to surrounding components in the VFD. Many researchers and application engineers have thought about this issue, and many are actively seeking nonmechanical solutions in a cost-effective manner. In this paper, a new topology to soft charge the dc-bus capacitor is proposed. Other techniques that have been evaluated are also introduced. The relative advantages and disadvantages are discussed. Experimental tests to show the feasibility of the proposed idea are also provided.

The spectral emission from thermographic phosphors in free flow and its dependence of laser energy per cross section area (laser fluence [J/cm2]) has been investigated. Temperature measurements in gaseous flows using thermographic phosphors require higher laser energy than measurements performed on surfaces, due to lower particle density. A troublesome systematic error associated with high fluences would be introduced if the excitation laser heats the particles. In the presented work, three different types of the thermographic phosphor BaMg2Al10O17:Eu (BAM) are investigated. Spectra of the phosphorescence are achieved for a range of laser fluences. The results show no indications of the laser heating the particles, making further development of phosphor thermography in free-flow applications feasible.

We investigated a field-effect transistor (FET) based on a poly(3-n-hexylthiophene) (P3HT) to determine the influence of moisture on device characteristics and thus gain a deep understanding of the mechanism underlying the susceptibility to air of the operation of FETs of this kind. The fundamental output characteristics, which include effective field-effect modulation and saturation behavior in the output current, remained almost the same for every current–voltage profile in a vacuum, N2 and O2. By contrast, operation in N2 humidified with water resulted in enlarged off-state conduction and deterioration in the saturation behavior, in the same manner as that experienced with exposure to room air. We concluded that atmospheric water had a greater effect on the susceptibility of the device operation to air than O2, whose p-type doping activity as regards P3HT caused only a small increase in the conductivity of the active layer and a slight decrease in the field-effect mobility with exposure at ambient pres...

We have proposed novel photoresponsive green- and blue-emitting organic electroluminescent (EL) devices combining organic EL diodes with titanyl phthalocyanine as a photoconductive layer. By irradiating red and near-infrared (IR) lights to these devices, green and blue emissions were generated, respectively, well below the turn-on voltage. The results indicate that the devices act as an optical switch and up-converter. The EL response time using a laser pulse was about 300 μs. Above the turn-on voltage, enhancement of the EL intensities was observed with the light irradiation with the ratio of up to 10 4 .

Time-resolved electric-field-induced sum-frequency generation (EFI-SFG) spectroscopy was employed to study the charge behavior of multilayer organic light-emitting diodes (OLEDs). Through application of the square wave pulse bias to the OLEDs, compensation for the polarization charges in the electron transport layer and the generation of 4,4'-bis[N-(1-naphthyl-N-phenylamino)-biphenyl] (α-NPD) cations were observed. When the pulse voltage was turned off, the α-NPD cations immediately disappeared, confirming that charge recombination occurs at the interfaces. We therefore concluded that time-resolved EFI-SFG is useful for directly probing the carrier behavior in OLEDs in addition to identifying the origin of the charge carriers present in OLEDs.

A novel polysilane, poly[(p-butoxyphenyl)phenylsilane] (PBPPS) has been synthesized and employed as an emissive layer of an organic electroluminescence (EL) device. PBPPS was spin-coated onto a uniaxially oriented poly(diethylsilane) (PDES) ultrathin film prepared by the friction-transfer method. We observed polarized, near-ultraviolet (UV) EL with its dichroic ratio of 2 from the polysilane-based multilayered EL device. Polarization direction was found to be identical with the drawing direction of the friction-transfer process for the PDES film, indicating that PBPPS in the emissive layer was aligned parallel to the uniaxial orientation of PDES. A depolarized, broad visible band appeared in the EL spectrum, which was absent in photoluminescence of PBPPS or PDES films. Origins of near-UV and visible EL components are discussed.

In order to understand the relationship between the molecular orientation and optical properties of oligophenylenevinylene film, oriented thin films of 1,4-di(p-methoxystyryl)benzene (DSB-1) and 1,4-di(p-methoxystyryl)-2,5-dimethoxybenzene (DSB-2) were fabricated on a potassium bromide (KBr) (001) surface by the vacuum-evaporation method. The structures and optical properties of DSB films have been investigated by transmission electron microscopy (TEM), atomic force microscopy (AFM) and polarized photoluminescence (PL) spectroscopy, respectively. DSB-1 molecules orient obliquely and/or parallel to the substrate surface depending on the substrate temperature. On the other hand, DSB-2 molecules tend to grow epitaxially with the molecular plane parallel to the substrate surface. The anisotropic molecular orientations represent the polarized PL. The epitaxial growth and molecular orientations observed by TEM and AFM at the local and microscopic scale are confirmed by polarized PL measurement on a macroscopic scale. (C) 1999 American Institute of Physics. [S0021-8979(99)01523-6].

A comparison of the transient electroluminescence (EL) between a microcavity organic light-emitting diode (MC-OLED) and a conventional OLED was performed and their carrier dynamics were discussed. We found that the behavior of transient EL in a MC-OLED can be accurately described using rate equations without exciton-carrier interaction for a conventional OLED, suggesting that carrier dynamics is not modified using a MC structure.

Under high current density, lots of organic electroluminescent devices (OELDs) exhibit a substantial decrease in an external quantum coefficient (ηext). Understanding the operating principles of the device is necessary to control the ηext roll off and achieve good performance of OELDs. In this study, we mainly discuss the possible dynamics of charge carrier in our device according to the transient behaviors of electroluminescence (EL) and current after voltage pulse was turn off. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Influence of back-channel electronic state on device characteristics was investigated for pentacene-based thin-film transistors (TFTs), where top surface of the semiconductor layer was covered with an LiF thin film. We observed higher field-effect hole mobility in the TFTs with the LiF-covered back channel than in the corresponding uncovered counterparts. In addition, the LiF-covered TFTs exhibited a decrease in turn-on voltages and an increase in off-state current depending on the thickness of the LiF layer and top- or bottom-contact configuration of the source and drain electrodes. We attributed the electronic effect brought about by the LiF coating to a downward band bending in the back channel originating from a rearrangement of the electronic energy-level alignment at the pentacene/LiF interface. The difference in the device characteristics from those of the uncovered TFTs was successfully explained by such electronic processes in the pentacene layer induced by the downward band bending in the back channel as a pseudo -back gate effect and generation of offsetting holes against the surface electronegativity. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

To fabricate “polarized” electroluminescence (EL) devices as a next generation, the growth mechanism of dye materials on several substrates, KBr, KCl, indium tin oxide (ITO) and quartz plate (fusued silica glass) was characterized by TEM and SEM to control the molecular orientations in films. The qualitative analysis of photo-luminescence (PL) from Tris(8-hydroxyqunoline) aluminum (Alq3) films epitaxially grown on KCl was done to confirm successively the anisotropic emission.

We report the observation of strong coupling between exciton and photon modes in a conjugated polymer-based semiconductor microcavity. Thin films of the σ-conjugated poly[bis(p-butylphenyl)silane] (PBPS) were inserted between metal and dielectric mirrors to form the microcavity structures. Variation of the PBPS film thickness between 80 and 140 nm allowed the cavity photon resonance to be tuned in the vicinity of the free exciton energy. The expected anticrossing behavior, with intensity and linewidth averaging, was observed at room temperature in the cavity reflection spectra and the vacuum Rabi splitting was found to be ⩽430 meV. This large value is consistent with the expectations of transfer matrix reflectivity calculations performed with optical constants data derived from a Kramers–Kronig analysis of the PBPS absorption spectrum. Angle-dependent photoluminescence measurements were performed for the microcavity with a 120 nm thickness PBPS layer. Unlike the emission from a standard, weakly coupled, c...

A photoresponsive organic light-emitting device combining blue-emitting organic electroluminescent (EL) diode with titanyl phthalocyanine as a near-infrared (IR) sensitive layer was fabricated. By irradiating near-IR light to the device, blue emission occurred in the lower drive voltage (between 5 and 12 V). The result indicates that the device acts as a light switch and/or an up-converter from near-IR light (1.6 eV) to blue (2.6 eV). The EL response times of rise and decay using a near-IR light trigger were 260 and 330 μs, respectively. At a higher voltage (above 12 V), enhancement of blue emission was observed with near-IR light irradiation. The ON/OFF ratio reached a maximum of 103.

Gallium Nitride (GaN) and Silicon Carbide (SiC) devices have been found to withstand high voltages without showing degradation [1] and can be switched at high frequencies making them attractive for high power drives. Though GaN/SiC devices can be operated at high temperature and high frequencies, it is important to develop gate drive circuits to turn ON and OFF these devices efficiently at high speeds. This paper proposes a resonant gate drive circuit that aims at reducing the power loss associated with high frequency switching of power IGBT/MOSFETs. The proposed circuit is compared with traditional gate drive circuits from power consumption and switching speed points of view. Experimental results are given to illustrate the concept.

The matrix converter has many advantages in wind power system applications. Matrix converter is compact and highly efficient because it directly converts generated power from AC generator to AC grid without intermediate DC bus while conventional back-to-back converter systems requires many electrolytic capacitors in DC link bus which are bulky and have short life-time. Matrix converter has both motoring and regenerative power flows keeping low harmonics current in grid. It also can provide reactive power to the grid, which is important characteristic for wind farms to stabilize power system during and after grid failure. In this paper, high power matrix converter is introduced for wind power applications. Major technical features and advantages are described. Experimental results with a PM generator show good feasibility for the wind power applications.

We have already reported that low-temperature (about 170 °C) preparation technique of silicon dioxide (SiO2) dielectric thin film that has high resistivity and extremely smooth surface by the photo oxidation process. In this paper, we have developed a low-damage preparation technique to fabricate a SiO2 thin film by the photo-assisted low temperature oxidation process in order to apply this process to the flexible electronics using for convenient plastic films. We have reported that the SiO2 dielectric thin film with a high insulation performance can be prepared by the low temperature processing below 100°C by improving the pre-processing of the photo oxidation of thin film.

Temperature stratification plays an important role in HCCI combustion. The onsets of auto-ignition and combustion duration are sensitive to the temperature field in the engine cylinder. Numerical simulations of HCCI engine combustion are affected by the use of wall boundary conditions, especially the temperature condition at the cylinder and piston walls. This paper reports on numerical studies and experiments of the temperature field in an optical experimental engine in motored run conditions aiming at improved understanding of the evolution of temperature stratification in the cylinder. The simulations were based on Large-Eddy-Simulation approach which resolves the unsteady energetic large eddy and large scale swirl and tumble structures. Two dimensional temperature experiments were carried out using laser induced phosphorescence with thermographic phosphors seeded to the gas in the cylinder. The results revealed different mechanisms for the development of temperature stratification: intake gas and residual gas mixing, heat transfer in the wall boundary layer, compression of the charge, and large scale flow transport. The sensitivity of LES results to different wall boundary conditions and inflow conditions was analyzed. (Less)

Variable Frequency Drives (VFDs) with diode rectifier front end are typically equipped with a resistor-contactor arrangement to limit the inrush current into the dc bus capacitors, thereby providing a means for soft charging the dc bus capacitors. Because of the mechanical nature of the magnetic contactor typically used in VFDs, there exists a concern for fatigue. In addition, during a brown out condition, typically the contactor remains closed and when the voltage recovers, the ensuing transient is often large enough to possibly cause unfavorable influence to surrounding components in the VFD. Many researchers and application engineers have thought about this issue and many are actively seeking non-mechanical solutions in a cost effective manner. In this paper, a new topology to soft charge the dc bus capacitor is proposed. Other techniques that have been evaluated are also introduced. The relative advantages and disadvantages are discussed. Experimental tests to show the feasibility of the proposed idea is also provided.

Diode rectifier with large DC bus capacitors, used in the front ends of Variable Frequency Drives (VFDs), draw discontinuous current from the power system resulting in current distortion and hence voltage distortion. Typically, the power system can handle current distortion without showing signs of voltage distortion. However, when the majority of the load on a distribution feeder is made up of VFDs, current distortion becomes an important issue. Multi-pulse techniques to reduce input harmonics are popular because they do not interfere with the existing power system either from higher conducted EMI when active techniques are used or from possible resonance, when capacitor based filters are employed. In this paper, a new 18-pulse topology is proposed that has two six-pulse rectifiers powered via a phase-shifting isolation transformer, while the third six-pulse rectifier is fed directly from the AC source via a matching-impedance. This idea relies on harmonic current cancellation strategy rather than the flux cancellation method and results in lower overall harmonics. It is also seen to be smaller in size and weight, and lower in cost compared to an isolation transformer. Experimental results are given to validate the concept.

Transient electroluminescence and transient current from organic light-emitting diodes were investigated by driving the device with short voltage-pulses. We discuss the possible operating mechanisms from these transient behaviors after the voltage pulse was turn off.

The spectral imaging for electroluminescence (EL) characterization in the light emitting diode (LED) based on blends of poly[2,7-(9,9-di-n-octylfluorene)] (PFO) and poly[2,7-(9,9-di-n-octylfluorene)-alt-(1,4-phenylene-((4-sec-butylphenyl)amino)-1,4-phenylene) ] (TFB) was performed using the two dimensional imaging micro-spectroscopy system. We found that EL spectral images varied with increasing applied voltages. The origin for such variation of EL spectral images will be discussed in this report.

The spectral imaging for electroluminescence characterization in a blend-polymer LED was performed. Electroluminescence spectral images varied with increasing applied-voltages. Such variation may originate from the transfer of emission site in a blend-polymer layer.

In order to develop a printable organic thin film transistor with high performance, it is required to develop not only printable materials and a printing process but also a suitable device structure for it. We have newly designed an organic field effect transistor with a diagonal configuration of source and drain electrode, named as the Top and bottom contact (TBC) configuration. It has several advantages due to its unique structure. For example, it can be prepared by a simple stacking process without any micro-machining process or related photolithography procedures. This is thus suitable for applying the simple printing technique such as a screen-printing. In the proposed structure, source and drain electrodes are arranged diagonally across the active layer. Therefore, the channel length can be controlled by the deposited active layer thickness. In this study, we have prepared the pentacene transistor with the TBC configuration. By inserting the extra insulator layer, leakage current between the top and bottom electrode was remarkably reduced. The output current density was about two orders larger than the conventional organic transistor with a top contact configuration. These high performances are mainly due to the improvement of the carrier injection efficiency owing to the short channel length (ca.0.5μm).

The strong coupling between exciton and photon modes in a conjugated polymer-based semiconductor microcavity was observed. The σ-conjugated poly(bis(p-butylphenyl)silane) (PBPS) thin films were inserted between metal and dielectric stack mirrors to form the microcavity structure. Change of the PBPS film-thickness (from 80 to 140 nm) allowed the cavity photon resonance to be tuned in the free-exciton transition. The expected anti-crossing behavior was observed at room temperature in the reflection spectra and the vacuum Rabi-splitting energy was found to be about 430 meV. This giant value is almost the same as the expectations of transfer matrix reflectivity calculations performed with optical constants (refractive index: n, extinction coefficient: k) derived from a Kramers-Kronig analysis of the PBPS absorption spectrum. Angle-dependent photoluminescence measurements were performed in each PBPS-based microcavity. In the microcavity with a 120nm-PBPS layer, the polariton emission that displays almost no blueshifts with angle was observed, a desirable feature for potential display applications.

An optical microcavity structure was introduced into organic three‐layer electroluminescent (EL) diodes with a europium complex as an emission layer. The device structure consisted of a dielectric reflector composed of SiO2/TiO2 bilayers, an indium‐tin‐oxide electrode, a hole transport layer, a europium complex as an emission layer, an electron transport layer, and a MgAg electrode. The dielectric reflector and the MgAg metal electrode constituted a planer microcavity. Sharply directed emission from the europium complex was observed when operated under dc drive voltage. Both angular dependences of intensity of emitted light and emission spectra of the EL diodes with the microcavity were compared with those of conventional EL diodes without microcavity.

An electroluminescent diode with a microcavity structure which comprised a reflective Ag anode (36 nm), a hole transport dye layer (250 nm), an emission dye laser (15 nm), an electron transport dye layer (240 nm), and a reflective MgAg cathode was fabricated. A diode without the microcavity structure with a transparent ITO anode was also prepared for reference. The diode with microcavity was driven in the electric excitation mode and emission spectra at fixed detection angles were measured together with the angular dependence of emission intensity at fixed wavelengths. A sharpening of emission spectra and a marked alteration of emission patterns in the diode with microcavity were observed.

Organic thin films composed of π-conjugated molecules have several interesting properties: semiconducting properties, photoluminescence and so on. The π-conjugated molecules are easily excited to their singlet states. The excited molecules are usually created not only by the absorption of UV-light but by the recombination of conducting electrons and holes. If one succeeds in utilizing these fundamental processes, one can propose organic electroluminescent (EL) devices, organic solar cells and so on.

Electric-field-induced doubly resonant sum-frequency generation (EFI-DR-SFG) spectroscopy was used to study the electric field distribution in multilayer organic light-emitting diodes (OLEDs). Remarkable correlations between the DR-SFG signal enhancement and the applied bias voltage were observed. The SFG signals attributed to 4,4′-bis[N-(1-naphthyl-N-phenylamino)-biphenyl] were significantly enhanced by applying a forward voltage, whereas those from Alq3 were increased by applying a reverse voltage. The large enhancement in EFI-DR-SFG intensity enables us to nondestructively probe the local electric field distribution at the buried organic layer within the OLED.

Summary form only given. Multilayer electroluminescent diodes with sharp red emission were fabricated using a new europium complex as an emitter. Microcavity structures were introduced into the EL diodes with sharp red emission. The device structures were composed of pairs of SiO/sub 2//TiO/sub 2/ dielectric reflector, indium-tin-oxide electrode, hole transport layer, europium complex as an emission layer, electron transport layer and MgAg electrode. The dielectric reflector and the MgAg metal electrode constituted a planer microcavity, and sharply directed emission from europium complex was observed when operated under dc drive voltage at room temprature. The relation between emission angle and the size of microcavity was discussed.

Oriented poly(2, 5-dimethoxy-p-phenylenevinylene), MOPPV, thin films were prepared by the Langmuir-Blodgett (LB) technique. In the MOPPV LB films, π-conjugated chains were biaxicially oriented. The π-conjugated chains were oriented along the dipping direction in addition to planar orientation. Further, mean π-conjugation length in the MOPPV LB film was extended in comparison with that in a conventional spin-coated MOPPV film which was obtained from an organic-solvent-soluble precursor polymer. Owing to the orientation of π-conjugated chains, the anisotropy of third-order susceptibility was observed in the MOPPV LB film; χ(3)|| = 4.5 × 10−10 esu χ(3)|| = 1.0 × 10−10 esu at fundamental wavelength of 1064 nm (two photon resonance region), and χ(3)⊥= 3-2 × 10−10 esu and χ(3)|| = 1.8 × 10−10 esu at fundamental wavelength of 1600 nm (three photon resonance region), where χ(3)|| and χ(3)⊥ are third-order susceptibilities parallel and perpendicular to the dipping direction, respectively.

Summary form only given. Control of spontaneous emission in organic elactroluminescant devices by using planar microcavity structures is demonstrated. Multilayer-dye electroluminescent devices which were composed of a hole transport layer, an emission layer and an electron transport layer were used. Semi-transparent metal films or an indium-tin-oxide transparent layer with a dielectric stack mirror as an anode and a highly reflective MgAg arroy film as a cathode costituted the Fabry-Perot cavity with spacings of the order of the wavelength of emission light. Firstly, the changes of emission lifetimes with the change of cavity-sizes, which evidenced the existence of the effect of confined radiation field in microcavities, were demonstrated. Secondly the change of both emission spectra and spacial distribution of emission patterns in electroluminescent devices with microcavity structures were studied. Finally, the realization of strongly-directed emission using the simple Fabry-Perot type electroluminescent devices with Europium-complex as an emission layer was demonstrated.

We developed the novel pressure-annealing method for fabricating printed low-work function metal patterns and printed metal alloy patterns. The printed diode having various rectification properties was successfully produced by using the printed metal alloy electrode pressure-annealed.