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In this study, we investigated the optimum thicknesses of organic light-emitting diode (OLED) layers using a high-reflectivity metal, Al, coupled with high-work-function alloys, e.g., AuSn, AuGe, and AuGeNi, as anodes, and LiF/Al/Ag multilayers as cathodes. The work function of a double-metal-layer, Al/AuGeNi (60/2 nm), was measured to be 4.7 eV, which is higher than that of a single Al layer of 4.2 eV. A high-work-function anode increased the number of holes injected from the anode into a hole transport layer and hence increased luminescence efficiency. After the optimization of each organic layer thickness, the device produced a maximum luminance of 2930 cd/m2 and a maximum luminance yield of 1.4 cd/A, which are the significant improvements of the performance characteristics of 537 cd/m2 and 0.28 cd/A obtained before the optimization of organic thickness, when the single Al layer was used as an anode, the device only exhibited a luminescence of 190 cd/m2 and a short lifetime.

Organic small molecule and polymer materials are being considered as solar cell material in place of silicon wafer. Organic solar cells are now a popular subject in international research. This study uses ZnPc and C60 as respectively the donor material and acceptor material of Organic Solar Cells (OSC) and examines the efiects of difierent blocking layers and structures (P-N junction and P-I-N structure) on open-circuit voltage (VOC), short-circuit current (ISC), flll factor (FF) and e-ciency of solar cell. It is found under the same thickness of 15nm, the short-circuit current generated by the BCP and BAlq3 blocking layers is respectively 1.36 and 1.19mA/cm 2 . This is because the BCP has higher energy gap and Highest Occupied Molecular Orbital (HOMO) than BAlq3, which enables BCP to block excitons and holes better. When the P-I-N structure is ZnPc(30nm)/C60(40nm) and ZnPc(30nm)/ZnPc:C60(20nm)/C60(40nm), the short-circuit current produced could be increased to 2.67mA/cm 2 respectively. This is because the intrinsic layer increases the contact area of P-N junction, enabling more excitons to dissociate into free charges. DOI: 10.2529/PIERS061010102724

This study employed poly(3,4-ethylenedioxy-thiophene):poly(styrenesulfonate) (PEDOT:PSS), 4,4'-bis[N-(1-naphthyl)-N-phenylamino]-biphenyl (α-NPD) and α-NPD/Teflon as buffer layers between the organic layer and indium tin oxide (ITO) of a flexible organic light-emitting diode (FOLED) to enhance the luminance efficiency of the device. PEDOT:PSS and α-NPD were spin-coated onto the ITO substrate, but α-NPD was first dissolved in chloroform. With the deposition of PEDOT:PSS of 40 nm thickness, the surface roughness of ITO decreased from 2.768 to 1.415 nm, whereas the luminance yield increased from 2.0 to 4.0 cd/A; the maximum luminance was 1500 cd/m2 at 44 mA/cm2. With the deposition of α-NPD of optimum thickness as buffer layer, the device had a luminance yield of 5.2 cd/A and a maximum luminance of 1220 cd/m2 at 25 mA/cm2. When the α-NPD buffer layer was further coated with a thin layer of Teflon by evaporation, i.e., α-NPD/Teflon (55/1 nm), the luminance yield of the device increased to 6.5 cd/A.

Red dopants were doped in different emitters, blue and green, respectively, to fabricate white organic light emitting diodes on flexible substrates. The competitive emission between blue and red emitters with various doped-zones was studied. When the DCJT doped zone was located far away from the hole-injection layer, both the blue and red color can be emitted. An appropriate red-dopant position in the device enhanced the green emission from 8-hydroxyquinoline aluminum (Alq3) which was combined with the red and blue emission to generate a white light. Finally, a white emission with the CIE value, (0.30, 0.32), independent of the applied voltage, was obtained with the optimum doped width and location.

The intrinsic and effective microwave surface impedances for a thin type-II superconducting film in the low and parallel DC magnetic field are calculated. We consider the case where the thickness of superconducting thin-film, d , is less than the penetration depth, λ L , and a row of vortices is present in the center plane of film. Firstly, we investigate the intrinsic surface impedance of a thin-film as a function of static field, film thickness, and radiation frequency as well. The contribution of the moving vortex chain to the intrinsic surface impedance will be numerically demonstrated. Next, we shall consider the resonant layered structure such as a superconducting thin-film deposited on a dielectric substrate and the resonant behavior in the effective surface resistance will then be examined in detail. The effect of vortex chain on the resonant phenomenon will be discussed and elucidated.

Light emitting diode (LED) has more advantages compared with a traditional incandescent light bulb and a fluorescent lamp, such as small size, low quantity of heat, long life, low power consumption, fast response, plain packaging and ease of develop ment of a frivolous short product. A methodology is proposed to improve the uniformity of the LED illumination system. As a light source in a backlight unit (BLU), the requirement for optical characteristics of a LED is different from highly directional conventional ones. New diffused-type LEDs need to be developed to fulfill the requirement of the BLU industry. A non-spherical lens is designed to optimize uniformity, and a great improvement in uniformity from 28.4 to 64% is demonstrated. In the future, it may used in an LED display to improve the unevenness of illumination.

We microwave characteristics of a multilayer structure made of a type-II superconducting thin film and a dielectric substrate together with a superconducting ground plane is studied theoretically by using the model of the self-consistent treatment of vortex dynamics. The dependence of reflection coefficient on the temperature and static magnetic field is reduced owing to the existence of the superconducting ground plane, especially at temperatures near T/sub c/ and at higher fields. Comparison of the interesting oscillation phenomenon in the associated effective surface resistance between the Meissner state (b=0) and mixed state (b/spl ne/0) is made. We find that the superconducting ground plane not only strongly narrows down the resonant peak shape but also enhances the peak height. Finally, a similar layered structure made of a superconducting thin film on a dielectric substrate shielded by a buffer layer is also considered. We specifically demonstrate that the buffer layer has essentially no substantial influence on microwave reflectance, transmittance, and complex surface impedance. The role played by the buffer layer is in great contrast to that in a planar transmission line.

In this research, the optimization of device structures of blue fluorescent organic light emitting diode (OLED) with WBH-301 doped with WBD-701 was fabricated. By adjusting the thickness of each layer in OLED structure as well as total thickness of device, the position of recombination zone was controlled and located in the central region of emitting layer (EML) that significantly increases device efficiency. The device showed the current efficiency of 8.7 cd/A at current density 50 mA/cm2 and with Commission Internationale de L’Eclairage (CIE) coordinates (x = 0.17, y = 0.34). This efficiency enhancement is important for understanding and further improving high-performance fluorescent OLEDs.

The use of numerical simulation method to study the current–voltage (I–V) of organic light emitting diode (OLED) has always been an effective method to upgrade the luminous efficiency of OLED. As the I–V theoretical simulation equations are based on injected carrier passing through Schottky barrier, and considering that carrier capturing defect and carrier mobility rate might be generated within the inner organic layer of Pool–Frenkel model, the study had made a comparison between the I–V theoretical model with a double-layer device and the experimental data, and proposed the best parameters for the theoretical model after careful adjustment and comparison to establish an optimal simulated numerical model with a double-layer OLED current–voltage. Finally, a study was made on the carrier capturing defect and mobility rate affected by electric field and temperature.

Using the Oliker's ellipses technology, this study designs a low-beam reflector for LED-based headlamps LED-based headlamp that fulfills the ECE regulation R112. The proposed LED-based headlamps provides a high optical efficiency of 89.13%.

An unexpected enhancement in the variation of the diffraction intensity due to a predominant three-wave coherent interaction is observed in a four-beam X-ray diffraction. This intensity anomaly is found to result from the modification of mode excitation and the competition between coherent and incoherent interactions in the diffraction process. This finding opens up a new way of solving the phase problem.

The organic light emitting diodes (OLEDs) [1] is a new-generation flat panel display with the advantages of self-luminescence, wide viewing angle (> 160°), prompt response time (~1 μs), low operating voltage (3~10 V), high luminance efficiency, high color purity, and easy to be made on various substrates. Therefore, it’s an important topic that how to improve the luminance efficiency, lifetime and the adhesion characters of ITO/organic interface of flexible OLEDs. Zugang Liu et al. reported that the NPB (HTL) is suitable in contact with the emission layer and when they form an energy ladder structure, the driving voltage decreased and the electroluminescent output increased [2]. Thus it can be seen, the hole transport layer [3-6] is very important to balance the injection of hole and electron, to increase the luminance efficiency and lifetime. In recent years, the hole buffer layer of device typically employs LiF [7], CuPc [8], Pani:PSS [9-10] or PEDOT:PSS [9-11] to improve the hole injection efficiency. In addition, a flexible substrate (PET, metal foil, etc.) surface is not completely smooth and will usually have spikes. After the organic thin film evaporates onto the ITO substrate surface the spikes will still exist. When the device is operated under high voltage or high current density, a heavy amount of electric current will concentrate at the spikes and damage the device by causing the device to short circuit, creating Joule heat. The luminance efficiency of the device will therefore be reduced producing shorter device lifetime. Thus, the PEDOT:PSS fabrication process uses spin-coating to obtain a thin film with a smoother surface than that produced by thermal deposition. Spin-coating enhances the organic material adhesion in subsequent processes, thereby directly affecting the performance of flexible OLED. For the above reason, this research dissolved hole transport material N,N’-diphenyl-N,N’-bis(1-naphthyl)1,1’biphenyl-4,4’’diamine (α-NPD), N,N’Bis(naphthalenel-yl) -N,N’-bis(phenyl)-benzidine (NPB) or α-NPD:NPB in tetrahydrfuran (THF) solvent and spin-coated the buffer layer onto ITO surface of flexible OLEDs. Phosphorescent dye gains energy from the radiative recombination of both singlet and triplet excitons [12], improving the internal quantum efficiency of fluorescent OLEDs (FOLEDs) typically 25% at maximum to nearly 100% [13]. Enhancing the luminance 8

The derivative of C60, i.e., PCBM, and P3HT (3-hexylthiophene) were dissolved in chloroform:dichlorobenzene mixed solvent, then spin-coated as the active layer for organic solar cells (OSC). The experimental parameters were studied carefully to obtain the optimum power conversion efficiency (PCE), including the solvent mixing ratio, spin-coating speed, annealing conditions for the active layer, etc. The OSC devices were packaged with glass and a newly developed UV-glue to improve the lifetime and PCE. Dichlorobenzene solvent has great effect upon the PCE. Changing the spin-coating speed and increasing the number of steps increased the PCE apparently to 1.4%.

In this study, we dissolved hole transport layer (HTL) material NPB in THF (tetrahydrofuran) solvant, and spin-coated the N,N'-Bis(naphthalene-l-yl)-N,N'-bis(phenyl)-benzidine (NPB) solution on the surface of Indium Tin Oxide (ITO) anode to enhance the luminance efficiency and lifetime of flexible phosphorescent organic light emitting diodes (POLEDs), where the 2,2',2''-(1,3,5-Benzinetriyl)-tris(1-phenyl-1-H-benzimidazole) (TPBi) was employed as hole blocking layer (HBL) and its thickness was optimized. Such an improvement in the device performance was attributed to the improved hole-electron balance. Finally, we employed 2,9-Dime-thyl-4,7-dphenyl-1,10-phenanhroline (BCP) or TPBi as hole blocking layer. The maximum luminance efficiency reaching 24.4 cd/A can be obtained.

In this work, we propose a radio frequency identification (RFID) transponder operating in the UHF range. The RFID transponder encompasses the RF front-end circuit and signal processing unit. Of which, the RF front-end circuit consists of the voltage multiplier, voltage regulator, bias circuit, power on reset (POR), clock generator and ASK modulator/demodulator. This work proposes a ring oscillation scheme for the clock generator in the RF front-end circuit, which is capable of generating the two clock signals it requires without the use of the capacitor, resistor and inductor. Such scheme not only reduces the area it may require for the three kinds of passive components, it also reduces the power consumption. By using the TSMC 0.35-mum CMOS technology, the proposed RFID transponder with an area of 0.31 mm2 is implemented based on the ISO 18000-6 standard where the clock generator consumes only 0.4 muW.

An integrated intelligent home video management system was proposed in this paper. Five different types of multimedia representative features were computed as the basis of the home video management system. With the aid of some machine learning techniques, such as SVM, neural network, adaboost algorithm, and the K-means clustering algorithm, we develop six main applications based on this system. These applications include detection of abnormal camera operation, shot boundary detection, fast-pan detection, face shot identification, key-frame extraction, and variable length video abstraction. Our system can help inexpert digital camcorder users manage their home video effectively in a smart way.

This paper presents a video object segmentation scheme based on global motion estimation and compensation. For video sequences with or without camera motion, we propose a unified approach to extract the moving object models. This approach combines both the spatial information from current frame and the temporal information derived from global motion compensated frame. Experimental results demonstrate the validity and performance of our work.

Solution-based processing was applied to fabricate green phosphorescent organic light-emitting diodes (OLEDs). EPH31 was used as a phosphorescent host, doped with guest dopant green phosphorescent Ir(ppy)3, and dissolved in chlorobenzene solvent to form the emitting layer. Device structural parameters were controlled by changing the spin coating speed of the emitting layer and hole injection layer [poly(3,4-ethylene dioxythiophene):poly(styrene sulfonate), PDOT:PSS] to adjust the thickness of the electron transport layer [tris(8-hydroxyquinolinato)aluminum, Alq3]. In addition, the differences in using CsF and LiF materials as the electron injection layer were investigated. A maximum current efficiency of 13.6 cd·A-1 was obtained at a high emitting layer spin coating speed. Despite the close resemblance in both the luminance intensity and current efficiency when using CsF and LiF as the electron injection layer, CsF devices had a low driving voltage. Smooth and stable films resulting from the spin coated hole injection layer, along with the control of the thickness of the electron transport layer (Alq3) and electron injection layer (CsF), effectively improved the performance of green OLEDs. The emitting layer host material (CBP) and three guest dopants [Firpic, Ir(ppy)3, and Ir(piq)2] were dissolved in toluene solvent during solution preparation to fabricate white OLEDs. The properties of the resulting solution-processed white PHOLEDs are a current efficiency of 2.4 cd·A-1 at 20 mA·cm-2 and CIE coordinates of (0.33, 0.33) at 9 V. Results of these experiments demonstrate that solution processing can be used as an alternative to and in conjunction with thermal evaporation.

This study is carried out to discuss how to reduce the driving voltage of blue phosphorescent organic light-emitting diodes (PHOLEDs) by using a thin double-emission layer. A hole transport-type host (TCTA) is inserted between the hole transport layer (TAPC) and the emitting layer (EML), constituting a buffer layer between them with the aim of improving charge carrier balance. Furthermore, in this study, we also utilize the interface between double light-emitting layers of devices by codoping them with a red phosphorescent dopant [Os(bpftz)2(PPh2Me)2]. An Os complex with a high-lying highest occupied molecular orbital (HOMO) energy level (trapping holes) is codoped at the interface between emitting layers and an exciton-formation zone is expanded to obtain a white PHOLED with high efficiency. From the results, the optimal structure of the white device exhibits a yield of 35 cd A-1, a power efficiency of 22 lm W-1, and CIE coordinates of (0.33,0.38) at a luminance of 1000 cd m-2. Furthermore, the power efficiency can be improved to 30 lm W-1 by attaching the outcoupling enhancement film.

The derivatives of C60, [6,6]-phenyl C61-butyric acid methyl ester (PCBM), and 3-hexylthiophene (P3HT) were dissolved in o-dichlorobenzene (DCB) solvent, and then spin-coated as an active layer for polymer solar cells. The experimental parameters including the spin-coating speed and drying conditions for the active layer, were studied carefully to obtain the optimum power conversion efficiency (PCE). In the active layer drying procedure, the DCB solvent saturated/unsaturated vapor pressure was adjusted by controlling the amount of solvent at a half-open capacity. The DCB solution was used to enhance the self-organization of the active layer of P3HT and to reduce the number of pure PCBM clusters. In the DCB optimum solution, the PCE of a polymer solar cell can be increased from 1.36 to 1.79%. The structure corresponds to a nano-to-micron scale ordering in the unsaturation-treatment films. In the optimum unsaturation procedure, the PCE of a polymer solar cell can be increased from 1.79 to 2.53%. Using two steps with optimum rotation speeds in the active layer spin-coating, the surface uniformity can be improved, with the PCE increased from 2.53 to 3.13%.

In this study N,N'-bis(naphthalen-1-yl)-N,N'-bis(phenyl)-benzidine (NPB) was dissolved in tetrahydrofuran (THF) solvent, and the resulting solution was spin-coated onto an indium tin oxide (ITO)-coated plastic substrate to form the first hole transport layer (HTL). A second hole transport layer of NPB was then deposited by thermal evaporation on the first HTL to produce a flexible organic light-emitting diode (OLED) with a double HTL structure. The luminance efficiency of a device with a double HTL structure is thereby improved. Utilizing spin-coated (NPB+THF)/evaporated NPB as the double HTL structure, the efficiency can reach 3.86 cd/A, and the lifetime is extended by 14.4% compared with that of the conventional single thermally evaporated HTL.

Polymeric solar cells (PSCs) with a derivative of C60 [[6,6]-phenyl C61-butyric acid methyl ester (PCBM)], and 3-hexylthiophene (P3HT) as active layers have been fabricated. The PSC devices were also packaged with glass and novel UV glues to improve their lifetimes and power conversion efficiencies (PCEs). After encapsulation with UV glue I, II, and III, the PCEs of PSCs reached 4, 4.82, and 6%, respectively, and their half-lifetimes increased to 16–18, 26–28, and 90 h, respectively, while the PCEs and half-lifetimes of PSCs without encapsulation were 3.76% and 2.5 h, respectively.

This paper reports on the separately-doped structures of organic light-emitting diodes (OLED) in which red dye 4-(dicyanomethylene)-2-methyl-6-(1,1,7,7-tetramethyljulolidyl-9-enyl)-4H-pyran (DCJT) was doped into the host emitting layer of tris(8-hydroxyquinoline)aluminum (Alq3) by means of ultrathin separate doping (like quantum wells). The parameters in the ultrathin layer, including its width, position, number and spacing between separately doped layers, were changed to study their effects on electroluminescence (EL) characteristics. Thin doped layers increase the luminance efficiency. When the ultrathin separately doped layers were in the vicinity of the NPB/Alq3 interface, where N,N'-diphenyl-N,N'-bis(1-naphthyl)-(1,1'-biphenyl)-4,4'-diamine (NPB) is used as a hole transport layer, luminance efficiency also increased. The highest luminance efficiency reaching 4 cd/A was achieved using a double ultrathin separately doped structure with optimum doping thickness and 2 nm of space between the two layers. The study also found that double ultrathin separately doped structures achieved better EL intensity than single or triple ultrathin separately doped structures.