High-efficiency red electrophosphorescent devices based on new osmium(II) complexes

In this paper, we report on highly efficient red-phosphorescent light-emitting diodes using a series of osmium complexes 1–3 doped into poly(N-vinyl-carbazole) (PVK) matrix as emitters, thermally stable 1,3,5-tris(4′-fluorobiphenyl-4-yl)benzene (F-TBB) as a hole-blocking layer, and Alq₃ as an electron injection layer. The CIE 1931 chromaticity coordinates of complexes 1–3 are around (0.650, 0.347), (0.681, 0.317), and (0.696, 0.302), respectively, and remain almost unchanged over a wide range of operation voltages. The maximum luminous efficiencies reached 7.0, 3.5, and 1.2 cd/A for devices based on 10 wt.% of osmium complexes 1, 2 and 3, respectively, even with air stable aluminum as the cathode. We systematically studied the dependence of device performance on the osmium doping concentrations. It was found that the best device performance was observed at 10 wt.% doping concentration for all three osmium complexes. Both maximum luminance and luminous efficiency increased with increasing osmium complex concentrations in the beginning and reached maximum at 10 wt.% doping concentration. However, a further increase in the doping level resulted in a reduction in both device brightness and efficiency due to concentration quenching and triplet–triplet annihilation. This is consistent with the absolute photoluminescence quantum yields of PVK thin films doped with different concentration of osmium complexes.     

Fabrication and characteristics of anode as an electrolyte reservoir for molten carbonate fuel cell

In order to design the anode of a molten carbonate fuel cell (MCFC) to serve as an additional electrolyte reservoir, the surface of a conventional Ni-10 wt.% Cr anode is modified with bohemite sol by means of a dip-coating method. After coating the bohemite sol on the nickel surface, the surface layer is change into lithium aluminate particles during the course of cell operation. This results in good electrolyte wettability compared with a bare nickel surface. Consequently, the surface modification makes it possible to increase the electrolyte filling contents in the anode pores from 25–30 to 50–60 vol.%. In addition, the anti-sintering ability is induced due to the presence of lithium aluminate particles between the nickel particles. These findings show that the surface modification can increase both the structural stability and the electrolyte loading of the anode.     

Hybrid power supplies: A capacitor-assisted battery

A hybrid electrochemical power supply is a concept that circumvents the need for designing any single power source to meet some extraordinary application requirement. A hybrid allows using components designed for near optimal operation without having to make unnecessary performance sacrifices. In many cases some additional synergistic effects appear. In this study, an electrochemical capacitor was employed as a power assist for a battery. An engine starting load was numerically modeled in the time domain and simulations were carried out. Actual measurements were then taken on the cranking of a diesel engine removed from a 5.0-tonne military truck and cranked in an environmental chamber. The cranking currents delivered by each power source were measured in the accessible current loops. This permitted the model parameters to be identified and, by doing that, studies using the analytical model demonstrated the merit of this hybrid application. The general system response of the battery/capacitor configuration was then modeled as a function of temperature. Doing this revealed electrical the interaction between the hybrid components. This study illustrates another case for advocating hybridized power systems.     

Microstructural heredity of the LaMgNi based electrode alloys during annealing

The present work aims on heredity effect between the as-cast and annealed microstructure in the LaMgNi based electrode alloys. Experimental and thermodynamic assessments demonstrate a series of solid state phase transformation reactions taking place successively during the annealing process. Phase constitution, grain size and micro-morphology of the as-cast alloys which have significant effect on the kinetics of the phase transition during annealing are considered to be closely related with the annealed microstructure. Appropriate increasing the casting cooling rate leads to fine microstructure and less LaNi₅ and (La,Mg)Ni₂, which is more favorable to development of high abundance of (La,Mg)₂Ni₇ after annealing.     

Effect of oxygen plasma treatment on air exposed MoOx thin film

Oxygen plasma (OP) treatment on air exposed molybdenum oxide (MoO_x) has been investigated with ultraviolet photoemission spectroscopy (UPS) and angle resolved X-ray photoemission spectroscopy (AR-XPS). It was found that the work function (WF) reduction of MoO_x by air exposure can be recovered partially by OP treatment on the surface. The overall recovery was measured to be slightly more than 64%, which was adequate to provide a hole extraction layer to many hole-conducting organic materials. The incompleteness of the WF recovery could be attributed to the formation of a very thin layer of oxygen rich absorbents on top of the evaporated MoO_x film after OP treatment. AR-XPS showed that OP treatment shifted the core levels of oxygen and molybdenum about 0.1 eV toward the lower binding energy (BE), and confirmed the existence of oxygen deficiency in the evaporated MoO_x film. We also investigated the electronic energy level evolution of copper phthalocyanine (CuPc) on MoO_x/ITO by UPS. With the deposition of CuPc on OP treated MoO_x we observed band bending and the highest occupied molecular orbital (HOMO) level of CuPc was almost pinned to the Fermi level, which indicates the possibility of efficient hole injection with the OP treated MoO_x film.     

Volatile composition of traditional and industrial Orujo spirits

In this study, fourteen samples of Galician Orujo spirit (seven from industrial and seven from homemade sources) were analysed by gas chromatography in order to determine their content in major volatile compounds, methanol, higher alcohols, aldehydes and esters. The main objective of this study was the establishment of the differences existing in the volatile composition of both groups of spirits, to identify the compounds whose presence is due, fundamentally, to the production process, either with reference to the raw material itself or to the latter distillation phase. The variance analysis of the results obtained indicates that, for most of the compounds, there are no significant differences (p<0.05) in concentration in either of the groups of spirits. However, those compounds whose formation is related with the processing and storage of the raw material show a higher concentration in the spirits from industrial origin. Among these compounds can be cited methanol, 1-hexanol, 1-propanol, ethyl lactate and ethyl acetate whose sensorial contributions are considered negative. On the other hand, 2-phenylethanol (an important aromatic compound that contributes a nuance of roses) shows a higher concentration in the homemade spirits, possibly because of an increased contribution of the tails fraction to the spirit, backed up by the lower average concentration of ethanol in these distillates.     

Analysis of pattern-dependent image placement of single-membrane stencil masks for electron-beam lithography

Large single-membrane stencil masks have been developed for electron-beam lithography. Since a large membrane induces large image placement (IP) error, which is pattern dependent, a method of correcting EB data has been studied to compensate the membrane distortion. In this study, firstly, the effect of crystal anisotropy of a Si membrane to the distortion is examined by making masks from blanks with different orientations. The influence of the anisotropy is found to be small and simulation based on isotropic modeling should be applicable. Secondly, a finite element method (FEM) called ANSYS and Pseudo-FEM are used to predict distortions for three masks with 8 mm-, 12 mm-, or 18 mm-square die of an opening ratio of 0.2 on a 24 mm-square membrane. The simulation results are compared with the results obtained in the experiment on anisotropy and a previous experiment. Qualitative agreement is observed between simulation and experiment but quantitative agreement is obtained only after introduction of adjustment factors. A suggestion is made to improve the IP correction scheme for EB data.