Search

Top-emission organic light-emitting diodes (TEOLEDs) that contain semi-transparent metal top cathodes and highly reflective anodes have been actively researched for display applications due to their many advantages such as their high aperture ratio, good color purity, and high efficiency. In this research, the technical design of TEOLEDs used in organic light-emitting diode (OLED) displays is reviewed, covering the optical theory with the microcavity effect, optical losses, and the importance of the Purcell effect in the optical calculation. The key methodologies for addressing the high efficiency and low driving voltage of TEOLEDs are also discussed.

Here, we report efficient and stable indium phosphide (InP) based inverted red quantum dot light-emitting diodes (QLEDs) using a new high mobility and deep HOMO level hole transport layer (HTL) and...

We demonstrate a dimethyl ketone treatment for structural modification of cross-linked poly(4-vinylphenol) (c-PVP) gate insulator in pentacene thin-film transistors (TFTs). Here, the dimethyl keton...

Long-term stability of the solid electrolyte interphase (SEI) and cathode-electrolyte interface (CEI) layers formed on anodes and cathodes is imperative to mitigate the interfacial degradation of electrodes and enhance the cycle life of lithium-ion batteries (LIBs). However, the SEI on the anode and CEI on the cathode are vulnerable to the reactive species of PF

The development of a flexible electronic skin (e-skin) highly sensitive to multimodal vibrations and a specialized sensing ability is of great interest for a plethora of applications, such as tactile sensors for robots, seismology, healthcare, and wearable electronics. Here, we present an e-skin design characterized by a bioinspired, microhexagonal structure coated with single-walled carbon nanotubes (SWCNTs) using an ultrasonic spray method. We have demonstrated the outstanding performances of the device in terms of the capability to detect both static and dynamic mechanical stimuli including pressure, shear displacement, and bending using the principles of piezoresistivity. Because of the hexagonal microcolumnar array, whose contact area changes according to the mechanical stimuli applied, the interlock-optimized geometry shows an enhanced sensitivity. This produces an improved ability to discriminate the different mechanical stimuli that might be applied. Moreover, we show that our e-skins can detect, discriminate, and monitor various intensities of different external and internal vibrations, which is a useful asset for various applications, such as seismology, smart phones, wearable human skins (voice monitoring), etc.

To attain high efficiency and stability in a top-emission organic light-emitting diode (TEOLED), the semitransparent metal cathode must have high transmittance, low absorbance, and uniform surface ...

Here, we report an efficient inverted red indium phosphide (InP) comprising QD (InP/ZnSe/ZnS, core/shell structure) light-emitting diode (QLED) by modulating an interfacial contact between the electron transport layer and emissive InP-QDs and applying self-aging approach. The red InP-QLED with optimized interfacial contact exhibits a significant improvement in maximum external quantum efficiency and current efficiency from 4.42 to 10.2% and 4.70 to 10.8 cd/A, respectively, after 69 days of self-aging, which is an almost 2.3-fold improvement compared to the fresh device. The analysis indicates the consecutive reduction in electron injection and accumulation in the emissive QD due to changes in the conduction band minimum of ZnMgO (0.1 eV after 10 days of storage) through a downward vacuum-level shift according to the aging times. During the device aging periods, the oxygen vacancy of ZnMgO reduces, which leads to lower the conductivity of ZnMgO. As a result, charge balance of the device is improved with the suppression of exciton quenching at the interface of ZnMgO and InP-QD.

We report a dispersion state of concentrated multiwalled carbon nanotube (MWCNT) suspensions depending on their iterative milling process. The rheological properties of concentrated suspensions prepared with different milling times were measured using a Couette-typed rotation rheometer, and their electrical characteristics were investigated via an LCR meter. The relationships of the rheological and electrical properties with the dispersion state of the MWCNT were examined. The results of both the rheological and electrical measurements indicated that the de-bundling and dispersion of the MWCNT induced by the iterative milling yielded a percolation microstructure and an electrically conductive structure.

There are some reports related to applications of ultraviolet (UV) and water to enhance the electrical performance of metal oxide thin-film transistors (TFTs). We recently discovered that treatment timing and treatment method are also important for a good metal oxide thin-film formation. There are different influences on the metal oxide TFTs' electrical properties based on the UV irradiation and water treatment timing. The field-effect mobility of TFTs treated with UV-irradiation and water, which was spin-coated on the UV-irradiated film after pre-annealing, increased to 4.71 cm²V-1s-1 and 6.41 cm²V-1s-1. This was higher than the 3.39 cm²V-1s-1 field-effect mobility of non-treated TFTs. On the other hands, TFTs which were fabricated by the same method, with only varying the treatment time, after post-annealing, exhibited the tendency to show a decrease in field-effect mobility to 1.93 cm²V-1s-1 and 1.32 cm²V-1s-1, gradually, showing a contrasting tendency with the former conditions.

Lateral double-diffused metal–oxide semiconductors (LDMOSs) have applications in various devices. In this letter, the characteristics of a proposed sensor application based on an LDMOS incorporating a floating gate are reported. Furthermore, the possible applications of the proposed device are explored. In addition to being applicable to the unmodified complementary metal–oxide–semiconductor process, the layout of our device can be optimized for ion detection purposes. The sensitivity results across a pH range of 1–12 were approximately 9.01, 8.52, 8.73, and 7.81 nA/pH for the polysilicon lengths of 3.5, 4, 5, and $6~\mu \text{m}$ , respectively. The linearities of the LDMOSs were approximately 0.941, 0.940, 0.949, and 0.950 for the same polysilicon lengths. The results show that the proposed device is pH-responsive and exhibits linearity throughout the pH detection experiment. This proves that the proposed device is suitable for application as an ion sensor.

Polymer-inorganic semiconducting composite (MCTP-Fe3O4) particles were fabricated by loading nanosized Fe3O4 on the microporous covalent triazine-based polymer (MCTP) through a chemical coprecipitation method and then applied to an electrorheological (ER) material. The structural and morphological images of MCTP-Fe3O4 composite were examined by scanning electron microscopy, transmission electron microscopy, and X-ray diffraction. Their magnetic property was also investigated by vibrating sample magnetometry. The chain structure formation of MCTP-Fe3O4 dispersed in silicone oil under an external electric field was confirmed using an optical microscope. The ER fluid based on MCTP-Fe3O4 was processed by dispersing the composite particles in an oil medium, and for comparison, an ER fluid based on pure MCTP was also prepared by the same process. The ER performance of two different ER fluids was scrutinized by a rotational rheometer, which demonstrated that MCTP-Fe3O4 showed better ER characteristics than MCTP-based ER suspension.

Herein, deep blue strong microcavity top‐emitting organic light‐emitting diodes (TEOLEDs) optimized by a low absorbed silver cathode and a narrow bandwidth emitter are reported for realizing high‐efficiency and narrow spectral characteristics. Usually, the Mg:Ag cathode is widely used as a semitransparent cathode in TEOLED devices due to its favorable reflectivity and proper electron injection ability. However, the high extinction coefficient of Mg causes a decrease in the microcavity effect, causing a low optical efficiency of devices. A Ag cathode is applied as a semitransparent cathode to modify the high absorption property for a strong microcavity blue OLED. At optimal conditions, the optically calculated device efficiency of TEOLEDs using a BPPyA emitter is 70.2 and 91.1 cd (A * y)−1 for Mg:Ag and Ag TEOLEDs, respectively. To further improve the device efficiency, an alternative emitter (DABNA‐NP‐TB) is applied which has a narrow bandwidth of 25 nm. The optically calculated efficiency enhancement in the TEOLED is about 23% compared with a control emitter, which is well correlated with the result of fabricated TEOLEDs.

We investigate the effects of environmental conditions on the electrical stability of spin-coated 5,11-bis(triethylsilylethynyl)anthradithiophene (TES-ADT) thin-film transistors (TFTs) in which crosslinked poly(4-vinylphenol-co-methyl methacrylate) (PVP-co-PMMA) was utilized as a gate insulator layer. Atomic force microscopy observations show molecular terraces with domain boundaries in the spin-coated TEST-ADT semiconductor film. The TFT performance was observed to be superior in the ambient air condition. Under negative gate-bias stress, the TES-ADT TFTs showed a positive threshold voltage shift in ambient air and a negative threshold voltage shift under vacuum. These results are explained through a chemical reaction between water molecules in air and unsubstituted hydroxyl groups in the cross-linked PVP-co-PMMA as well as a charge-trapping phenomenon at the domain boundaries in the spin-coated TES-ADT semiconductor.

The optical characteristics of nanoparticles will vary according to particle size. With decrease in the size of the nanoparticle (NP), the bandgap of the material increases, thus providing a blue-shift in the refractive index of the material. In this study, we analyzed the effect of different sized zinc oxide (ZnO) nanoparticle optical spacer on the ideal short-circuit current density (Jsc,ideal) of an hybrid photovoltaic cell. ZnO was used as an optical spacer in the solar cell structure to improve the light absorbed in the active layer. Refractive index and extinction coefficient of different sized ZnO nanoparticles were calculated using tight binding model. We implemented these results in two different morphological models: nanoparticle model, and thin-film model. In the nanoparticle model, the ZnO NPs were considered as nanospheres which scatter the incoming light. Comparison of these models helped us to evaluate the improvement in the Jsc,ideal due to scattering effects from nanoparticles. Finally, the optimized structure was obtained for different active layer thicknesses by varying the thickness of the ZnO layer.

A new observation processing system, the Korea Institute of Atmospheric Prediction Systems (KIAPS) Package for Observation Processing (KPOP), has been developed to provide optimal observation datasets to the data assimilation (DA) system for the Korean Integrated Model, KIM. This paper presents the KPOP’s conceptual design, how the principal modules have been developed, and some of their preliminary results. Currently, the KPOP is capable of processing almost all observation types used by the Korea Meteorological Administration (KMA) and some new observation types that have a positive impact in other operational centers. We have developed an adaptive bias correction (BC) method that only uses the background of the analysis time and selects the best observations through the consecutive iteration of BC and quality control (QC); it has been verified that this method will be the best suited for the KIAPS DA system until the development of variational BC (VarBC) has been completed. The requirement of considering the radiosonde balloon drift in the DA according to the increase of spatial resolution of the NWP model was accounted for using a balloon drift estimation method that considers the pressure difference and wind speed; thus the distance error was less than 1% in the sample test. Some kind of widely used methods were tested for height adjustment of the SURFACE observation, and a new method for temperature adjustment was outlined that used the correlation between temperature and relative humidity. In addition, three types of map projection were compared: the cubed-sphere (CS), equidistance (ED), and equirectangular (ER) projection for thinning. Data denial experiments were conducted to investigate how the KPOP affected the quality of the analysis fields in the three-dimensional variational data assimilation system (3D-Var). Qualified observations produced by the KPOP had a positive impact by reducing the analysis error.

We investigated the variation in the electrical characteristics of solution-processed indium oxide (In2O3) thin-film transistors (TFTs) under monochromatic illumination conditions at different wave...

In this study, we executed optical simulations to compute the optimum power conversion efficiency (PCE) of a-Si:H/organic photovoltaic (OPV) hybrid tandem solar cell. The maximum ideal short circuit current density (Jsc,max) of the tandem solar cell is initially obtained by optimizing the thickness of the active layer of the OPV subcell for varying thickness of the a-Si:H bottom subcell. To investigate the effect of Haze parameter on the ideal short-circuit current density (Jsc,ideal) of the solar cells, we have varied the haze ratio for the TCO electrode of the a-Si:H subcell in the tandem structure. The haze ratio was obtained for various root mean square (RMS) roughness of the TCO of the front cell. The effect of haze ratio on the Jsc,ideal on the tandem structured solar cell was studied, and the highest Jsc,ideal was obtained at a haze of 55.5% when the thickness of the OPV subcell was 150 nm and that of the a-Si:H subcell was 500 nm.

The hysteresis of the solution-processed oxide thin-film transistors (TFTs) is fatal issue to interrupt stable operation. So, we came up with uni-directional pre-annealing to solve the problem. There are inevitable defects when solution-processed oxide TFTs are fabricated, due to the porosities by the solvent volatilization. Also oxygen vacancies needed for carrier generation in metal oxide semiconductor can be trap states inducing charge carrier trapping. Uni-directional pre-annealing improved the hysteresis, preventing randomly solvent evaporation and decreased the defects of the film. We can result in advanced stability of the solution-processed oxide TFTs, at the same time showing that the field effect mobility was enhanced from 3.35 cm2/Vs to 4.78 cm2/Vs simultaneously, and exhibiting better subthreshold swing from 0.89 V/dec to 0.23 V/dec.

We present a low absorption semi-transparent cathode for top-emitting organic lighting diodes (TEOLEDs). To reduce the light loss by electrode absorption, transparent cathode materials with a high refractive index and low extinction coefficient characteristics at the visible light range are investigated for the highly efficient TEOLEDs. Molybdenum trioxide (MoO3) and tungsten trioxide (WO3) are considered as the transparent materials. Due to the low conductivity of MoO3 and WO3, a small amount of silver (Ag) is blended in order to enhance the electrical property as electrodes. Optimized MoO3:Ag mixed film shows the reduced extinction coefficient by half compared to Mg:Ag. With a general organic material (refractive index∼1.8) as a capping layer, the average absorption, transmittance and omnidirectional reflectance of 18.2, 65.9, and 25.6% are observed, respectively, with a sheet resistance of 12.7 Ω/□. The current efficiencies of fabricated red, green and blue TEOLEDs with optimized MoO3:Ag cathode are 32.4, 76.8, and 2.8 cd/A, respectively. The performance enhancement ratio is 9.8, 13.6, and 86.7% for red, green and blue devices compared with Mg:Ag cathode devices.

We propose a feasible method of manipulating the surface energy of crosslinked poly(4-vinylphenol) (c-PVP) thin films through the surface compositional modification assisted by an etchant. A physical picture of the surface-energy manipulation of c-PVP thin films based on the surface-selective molecular subtractive approach is clarified by investigating the chemical composition of the c-PVP film surfaces. We reveal that the molecular detachment by solvation on the surface leads to a reduction in the surface PVP density, thereby decreasing residual hydroxyl groups on the surface. In particular, it is found that the surface energy of a c-PVP thin film can be controlled by exploiting the thermal-treatment-time dependence of the soluble-PVP density. Organic thin-film transistors (TFTs) are fabricated via a solution process for demonstrating the applicability of our surface-energy-engineered c-PVP film as a gate insulator. The TFTs with the engineered c-PVP gate insulators exhibit improved electrical characteristics, compared to those with ordinary c-PVP gate insulators.

In this paper, we report an optical structure design method with the predicted performances of highly efficient three-stacked white organic light emitting diodes (WOLEDs) for solid state lighting applications. The efficiency and color properties of stacked WOLEDs are strongly affected by optical interference inside the thick cavity length; therefore appropriate emissive layer (EML) position is determined by thorough theoretical optical simulations to prevent such optical effect. The theoretically evaluated, three-stacked hybrid WOLED with entirely separated phosphorescent red and green as well as fluorescent blue EML has displayed a CRI and power efficiency of 91 and 33.5 lm/W, respectively. Based on our assumptions, design method, and optical simulation results, the fabricated three-stacked WOLEDs showed a CRI of 93, external quantum efficiency (EQE) of 49.4%, and power efficiencies of 33.4 lm/W. These experimentally measured characteristics are fully correlated with the performances of optically simulat...

Clinical implications of neurological problems during intensive care unit (ICU) care for coronavirus disease 2019 (COVID-19) patients are unknown. This study aimed to describe the clinical implications of preexisting neurological comorbidities and new-onset neurological complications in ICU patients with COVID-19. ICU patients who were isolated and treated for COVID-19 between 19 February 2020 and 3 May 2020, from one tertiary hospital and one government-designated branch hospital were included. Clinical data including previous neurological disorders were extracted from electronic medical records. All neurological complications were evaluated by neurointensivists. Multiple logistic regression analysis was performed to investigate independent factors in ICU mortality. The median age of 52 ICU patients with COVID-19 was 73 years. Nineteen (36.5%) patients had preexisting neurological comorbidities, and new-onset neurological complications occurred in 23 (44.2%) during ICU admission. Patients with preexisting neurological comorbidities required tracheostomy more frequently and more ventilator and ICU days than those without. Patients with new-onset neurological complications experienced more medical complications and had higher ICU severity score and ICU mortality rates. New-onset neurological complications remained an independent factor for ICU mortality. Many COVID-19 patients in the ICU have preexisting neurological comorbidities, making them at a high risk of new-onset neurological complications.

In this paper, we report two new phenanthroline-based compounds, 1,4-bis(2-phenyl-1,10-phenanthrolin-4-yl)benzene (p-bPPhenB) and 1,3-bis(2-phenyl-1,10-phenanthrolin-4-yl)benzene (m-bPPhenB), for the charge generation unit of tandem organic light-emitting diodes (OLEDs). These two compounds exhibited high electron mobility of (5.8–4.4) × 10–3 cm2/(V s), a very small injection barrier at the p–n junction interface, a high glass transition temperature of 123.9–182.1 °C, and exceptionally good operational stability. Because of such excellent characteristics, a single-stack red phosphorescent OLED (PhOLED) with p-bPPhenB showed a low driving voltage (2.7 V) and significantly improved maximum power efficiency (56.8 lm/W), external quantum efficiency (30.8%), and device lifetime (LT95, 130 h) compared to those of the control device using bathophenanthroline (Bphen) (3.7 V, 39 lm/W, 27.1%, and 13 h). Furthermore, a two-stack (tandem) red PhOLED using p-bPPhenB in the charge generation unit exhibited superior cha...

Optical spacer interlayers are commonly used in solar cells to improve the power conversion efficiency (PCE) of the device. This paper reports a study on the effect of zinc oxide (ZnO) optical spac...

Two dissimilar materials, aluminum alloy Al5083-O and advanced high strength steel DP590, were successfully joined by using friction stir spot joining (FSSJ). Satisfactory joint strengths were obtained at a rotational speed of 300 rpm and a plunge depth of 0.7 mm. Resulting joints were welded without a non-welded zone. This may be attributed to the enhanced smooth material flow owing to sufficient stirring effect and tool down force between the upper Al5083-O side and the lower DP590 side. The maximum tensile shear strength was 6.5 kN, which was higher than the joint strength required by the conventional method of resistance spot welding. The main fracture mode was plug fracture in the tensile shear test of joints. An intermetallic compound (IMC) layer with

In this study, we investigate the morphological effect of solution-processed indium-zinc-oxide (InZnO) active layers on the electrical stability of InZnO thin-film transistors (TFTs). We first observe that in the spin-coating method, precursor agglomerates and aggregates remain on the substrates after spin coating an InZnO solution at a low spin speed, thereby causing particle-type morphological defects in the InZnO films. The morphological defects are proven to degrade the basic performance parameters of the InZnO TFTs, including the electrical current level, field-effect mobility, and threshold voltage. In addition, devices having morphological defects show a relatively large hysteresis in transfer characteristics compared to those without defects. In a test of the electrical stability over time, we determine that particle-type morphological defects cause a rapid increase in the conductivity of the InZnO films, which affects the variations in the saturation drain current and the threshold voltage.

The three-dimensional wind field (WPR3D) and the multiple WPR3D (M-WPR3D) associated with the passage of a stationary front was derived from observations made by a network of eight wind profiler radars (WPR) being operated by the Korea Meteorological Administration during the summer &ldquo, Jangma&rdquo, season. The effectiveness of the WPR3D was determined through numerical model analysis and wind profilers at three sites, and the accuracy of the M-WPR3D was validated by comparing the trajectory of the radiosonde. The discontinuity of the wind field near the frontal interface was clearly retrieved and the penetration of the air mass in the southern front was detected. Compared with either the wind vector of three single wind profiler or a local data assimilation and predication system, the WPR3D wind field showed a wind speed accuracy of approximately 70% at an altitude of 1.5 km and underestimated the wind speed by 0.5&ndash, 1.5 m s&minus, 1. The M-WPR3D with three S-band Doppler radars successfully retrieved the backing wind field as well as the pre-Jangma-frontal jet. The results of this study showed that severe weather can be effectively analyzed using a three-dimensional wind field generated on the basis of a remote sensing network.

In this work, sensible heat flux estimated using a bulk transfer method was validated with a three-dimensional ultrasonic anemometer or surface layer scintillometer at various sites. Results indicate that it remains challenging to obtain temperature and wind speed at an appropriate reference height. To overcome this, alternative observations using an unmanned aerial vehicle (UAV) were considered. UAV-based wind speed and sensible heat flux were indirectly estimated and atmospheric boundary layer (ABL) height was then derived using the sensible heat flux data. UAV-observed air temperature was measured by attaching a temperature sensor 40 cm above the rotary-wing of the UAV, and UAV-based wind speed was estimated using attitude data (pitch, roll, and yaw angles) recorded using the UAV’s inertial measurement unit. UAV-based wind speed was close to the automatic weather system-observed wind speed, within an error range of approximately 10%. UAV-based sensible heat flux estimated from the bulk transfer method corresponded with sensible heat flux determined using the eddy correlation method, within an error of approximately 20%. A linear relationship was observed between the normalized UAV-based sensible heat flux and radiosonde-based normalized ABL height.

This paper presents an efficient and stable green inverted organic light emitting diode (IOLED) using multifunctional and strong nucleophilic quality electron transport material (1,3-bis(2-phenyl-1,10-phenanthrolin-4-yl)benzene (m-bPPhenB)) with silver (Ag) as an n-dopant. By the energy level alignment study using in-situ ultraviolet photoelectron spectroscopy measurement, negligible electron injection barrier between indium tin oxide (ITO) and Ag-doped m-bPPhenB (Φe ≈ 0.03 eV) is observed and the electrons can be easily tunneled from ITO into Ag-doped m-bPPhenB layer. Also, Ag dopant forms coordination bonds with phenanthroline based unit, which improves electron injection from ITO. Fabricated IOLED devices using an Ag-doped m-bPPhenB have an extremely low driving voltage of 3.6 V and external quantum efficiency of 29.0%. Such good performances of IOLED are attributed to negligible electron injection barrier at the interface between ITO and Ag-doped m-bPPhenB. The Ag-doped IOLED device also shows a good air stability owing to the stable Ag n-dopant. The doping of Ag into special electron transport layer in the IOLED structure could be applicable to various displays and lighting applications.

In this paper, we report effectiveness of microstructured scattering layer and their efficient light trapping mechanism for performance improvement of polymer solar cells (PSCs). Our simple roll-to-roll processed polymeric scattering layer is an intrinsic and economical way to harvest more light in the photoactive layer of PSC׳s. An inverted polymer solar cell with microstructured scattering layer and photoactive layer of poly[4,8-bis(5-2-ethylhexyl)thiophen-2-yl]benzo[1,2-b;4,5-b′]dithiophene-2,6-diyl-alt-(4-(2-ethylhexyl)-3-fluorothieno[3, 4-b]thioph-ene-(-2-carboxylate-2-6-diyl)(PTB7-Th) and [6,6]-phenyl C 61 butyric acid methyl ester (PC 60 BM) exhibit a maximum power conversion efficiency of 8.60% under simulated AM 1.5G illumination at light intensity of 100 mw/cm 2 . A significant improvement of over 15% in short circuit current density of the solar cell devices is achieved by means of suppressing Fresnel reflection at the glass and air interface. In addition, wetting properties and optical simulation of the PSC׳s with and without scattering layer are performed using water contact angle measurement and SETFOS 4.1 module. We expect that this methodology will be advantageous for the development of future organic solar cells.

In this paper, the applicability and usefulness of windprofiler input data were investigated to generate three dimensional wind field. A logical diagnostic model CALMET with windprofiler data at ten sites and with weather forecasting model WRF output was evaluated by statistically comparing with the radiosonde data at eight sites. The horizontal wind speed from CALMET simulated with hourly windprofiler data is in good agreement with radiosonde observations within 1.5 m/s of the root mean square error, especially local circulation of wind such as sea breeze over the coastal region. The root mean square error of wind direction ranged is due to the wind direction error from the windprofiler polluted by ground clutters. Since the exact wind can be produced quickly and accurately in most of the altitude with windprofiler data on CALMET, we expect the method presented in this study to be useful for the monitoring of safe environment as well as weather in the coastal zone.

We report bipolar host materials with robust indenocarbazole and biphenyl moiety as hole-electron-transporting unit for phosphorescent yellow organic light-emitting diodes (OLEDs). New host materials demonstrated an excellent morphological stability with high glass transition temperature of 207 °C. Simultaneously, it also revealed appropriate triplet energy of about 2.6 eV for ideal triplet energy transfer to yellow phosphorescent dopant. A phosphorescent yellow OLED with new host ICBP1 (and ICBP2) and conventional yellow dopant iridium(III)bis(4-(4-t-butylphenyl)thieno[3,2-c]pyridinato-N,C2′)acetylacetonate (Ir(tptpy) 2 acac) shows a low driving voltage of 3.4 (and 3.6 V) at 1000 cd/m 2 , and maximum external quantum efficiency as high as 26.4%. Such efficient performance of phosphorescent yellow OLEDs is attributed to a good charge balance and high electron transport properties of host materials.

When a continuous welded rail(CWR) track is supported by bridge, additional axial stress and displacement are occurred by track-bridge interaction, and they have an effect on safety and serviceability of track. Domestic and foreign standards for track-bridge interaction offer analysis methods and limit values which are guiding the safety design, because the influence on interaction is difficult to be evaluated quantitatively. In this study, measurement system was constructed on the concrete a track supported by a bridge, and field monitoring has been carried out to evaluate the influence on track-bridge interaction by temperature changes. And track-bridge interaction responses under various temperatures were analyzed by comparing results of measurement and numerical analysis.

Two new blue emitting heteroleptic Ir(III) complexes containing a difluorophenylmethylpyridine (fpmpy)-based main ligand and a carbene-based ancillary ligand were synthesized: bis[2-(4,6-difluorophenyl)-4-methylpyridinato-C2,N](1′-(4′-fluorophenyl)-3′-methylbenzimidazole)iridium(III) and bis[2-(4,6-difluorophenyl)-4-methylpyridinato-C2,N](1′-methyl-3′-phenylbenzimidazole)iridium(III). The synthesis, X-ray crystal structures, photophysical and electrochemical properties, and PhOLED performance of both Ir(III) complexes are described. The two Ir(III) complexes showed very similar UV–visible absorption spectra irrespective of the presence of the fluorine atom in the ancillary ligand. The photoluminescence spectrum of the complex with the additional fluorine atom showed double emission bands at 464 and 482 nm in dichloromethane solution, whereas the alternate complex, without the extra fluorine atom, only exhibited a single emission at 487 nm. Both Ir(III) complexes were utilized for blue PhOLEDs with an identical device configuration. The complex with the additional fluorine atom exhibited an external quantum efficiency of 4.2%, which was higher than that of the alternate complex (3.5%).

Results on the device performances of 3rd order micro-cavity effects in green top emitting organic light emitting diodes (TEOLEDs) with optical spacer layer are reported. The performances of fabricated 3rd order micro-cavity green devices using fac-tris(2-phenylpyridine)iridium [Ir(ppy)3] green phosphorescent emitter and magnesium silver alloy semi-transparent cathode are systematically compared with the 2nd order cavity device. The optical and electrical simulation results of the 3rd order cavity device with emissive layer (EML) located near the semi-transparent cathode shows a current efficiency (CE) of 71.0 cd/A (70% value of the 2nd order device) and more serious color coordinates shift as compared to the 2nd order cavity device. With the center EML positioned 3rd order cavity device similar color variation behavior is observed but the CE value is 73.8 cd/A (73% value of the 2nd order device). The fabricated 3rd order TEOLEDs exhibit about 65–75% CE values of the 2nd order device as the simulation. Additionally, the viewing angle characteristics are significantly improved in the 3rd order center EML TEOLEDs as the simulation. The performances of fabricated TEOLEDs with 3rd order micro-cavity conditions are in quite good agreement with the optical and electrical simulation results.

New large-bandgap host materials with carbazole and carboline moieties were designed and synthesized for high-performance blue phosphorescent organic light-emitting diodes (PhOLEDs). The two kinds of host materials, 9-(4-(9H-carbazol-9-yl)phenyl)-6-(9H-carbazol-9-yl)-9H-pyrido[2,3-b]indole (pP2CZCB) and 9-(3-(9H-carbazol-9-yl)phenyl)-6-(9H-carbazol-9-yl)-9H-pyrido[2,3-b]indole (mP2CZCB), displayed promisingly high triplet energies of ∼2.92–2.93 eV for enhancing the exothermic energy transfer to bis[2-(4,6-difluorophenyl)pyridinato-C2,N](picolinato)iridium(III) (FIrpic) in PhOLED devices. It was found that the blue PhOLEDs bearing the new host materials and the FIrpic dopant exhibited markedly higher external quantum efficiencies (EQEs) than a device made with 1,3-bis(N-carbazolyl)benzene (mCP) as the host. In particular, the PhOLED device made with 3 wt% FIrpic as the dopant and mP2CZCB as the host material displayed a low driving voltage of 4.13 V and the high EQE of 25.3% at 1000 cd m−2.

We investigated the influence of pentacene film thickness on the environmental stability of thin-film transistors (TFTs). In order to evaluate the environmental stability, the transfer and output characteristics in pentacene TFTs were measured in air and vacuum environments. The pentacene-thickness-dependent variation of transfer characteristics was shown to originate from the fixed charge at the pentacene/polymeric insulator interface induced by air molecules. In addition, an analysis of parasitic resistance suggests that air molecules degraded the contact property and increased channel conductivity. Particularly, a thick pentacene film was found to passivate the TFT channel region interrupting the penetration of air molecules.

Rain attenuation can hinder the implementation of quantitative precipitation estimations using X-band weather radar. Numerous studies have been conducted on correcting the attenuation of radar reflectivity by utilizing a dual-polarimetric radar and an arbitrary-oriented microwave link; however, there is a need to optimize the required number of microwave links and their locations. In this study, we tested four attenuation correction methods and proposed a novel algorithm based on the sole use of adjacent multiple microwave links. The attenuation of the X-band radar reflectivity was corrected by performing forward iterations at each link, and the correction coefficients were statistically analyzed to reduce the instability problem. The algorithms of each method were evaluated by studying the cases of convective and stratiform rainfall, and then validated by comparing the corrected reflectivity of the X-band radar with the qualitatively controlled reflectivity of the S-band radar. The new method was as efficient as the conventional method based on the specific differential phase of dual-polarimetric radar. Furthermore, the correction coefficient was more effectively optimized and stabilized using seven microwave links rather than a single link, and no further independent reference data were required. In addition, the attenuation correction also accounted for spatiotemporal differentiation depending on the rainfall type, and could recover the physical structure of the rainfall. The method developed herein can facilitate estimations of quantitative rainfall in developing countries where dual-polarization weather radars are not common. The exploitation of microwave link data is a promising method for rainfall remote sensing.

Here, we report a highly reliable and transparent cathode (TC) for transparent organic light emitting diode (TOLED) applications. The cathode layer is fabricated by co-deposition of silver (Ag) and aluminum (Al) metals using thermal evaporation. The atomic percentages of Al and Ag are fixed at 96 at% and 4 at%, respectively. TC shows transmittance at 520 nm (T@520nm) of 83.5% and sheet resistance as low as 7.0 Ω/□. Almost no specific agglomeration of Ag:Al (4%, 14 nm) is noticed by the thermal annealing of fabricated cathode at 85 °C, 240 h. The fabricated TOLED with this Ag:Al (4%, 14 nm) cathode shows an excellent electron injection property with a T@520nm of 83.5%, and achieved current efficiencies of 36 and 18 cd/A from bottom and top sides emissions, respectively. It is argued that the Al-doped Ag film could become an effective, feasible alternative to the existing transparent conducting electrode for TOLED applications.

International audience; We describe the importance of active layer positioning for a gate electrode in organic thin-film transistors (TFTs). For this study, we utilizea numerical simulation based on 2-D Atlas, which is a two-dimensional technology computer aided design (so called 2D TCAD) software tool created by Silvaco. Variation in the electrical characteristics of pentacene TFTs is systematically explored by changing the mismatch length (L M) between the active layer and gate electrode in the bottomgate top-contact configuration. It is found that as the L M increases, the electrical performance of pentacene TFTs is exponentially degraded in terms of drain current on/off characteristics. In particular, we explain this phenomenon by examining variations in charge distribution and gate electric field in the TFT channel region byincreasing the L M .