Y3Al5O12:Ce3+ (YAG:Ce3+) nanocrystals were synthesized in 1,4-butylene glycol (BG) with and without poly(ethylene glycol) (PEG) by the glycothermal method. The internal quantum efficiency of the photoluminescence (PL) corresponding to the 5d --> 4f transition of Ce3+ in the YAG:Ce3+ nanocrystal increased from 21.3 to 37.9% by addition of PEG, while no appreciable change in the primary particle size, the crystallite size, and the lattice distortion was recognized by transmission electron microscopy and X-ray diffractometry. The thermogravimetry-differential thermal analysis, Fourier transform infrared absorption spectroscopy and 1H --> 13C cross-polarization magic angle spinning nuclear magnetic resonance (CP-MAS NMR) confirmed the preferential coordination of PEG to the YAG:Ce3+ nanocrystal. 27Al single-pulse excitation MAS NMR reveals that the ratio of the 4-fold coordination site to the 6-fold coordination site increased from 0.53 to 0.72 by addition of PEG. We conclude that the surface modification of the YAG:Ce3+ nanocrystal by PEG induces the surface passivation, the prevention of the oxidation of Ce3+ to Ce4+, the promotion of the incorporation of Ce3+ into YAG and the local structural rearrangement, resulting in the PL enhancement.

The authors produced the transparent color conversion thick film which is composed of a high concentration of YAG:Ce3+ nanoparticles prepared by glycothermal method, and characterized its optical properties. The transmittance of the 200μm thick film with the nanoparticle content 70.7wt% was 82% at 525nm corresponding to the emission peak of YAG:Ce3+. The intensity of photoluminescence due to the 5d→4f transition of Ce3+ in YAG:Ce3+ nanoparticles was doubled by placing a reflection mirror at the back of the transparent film. Judging from this result, the transparent film of YAG:Ce3+ nanoparticles has markedly low scattering loss.

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The concept of van der Waals solid solutions has been demonstrated to yield photon upconversion (UC) organic crystals with extraordinary performance, opening a domain of versatile dispersion-force-based systems in the quest for superior UC solids.

The authors applied two technologies to improve the efficiency of fluorescent blue organic light-emitting diodes (OLEDs). First, an efficiency-enhancement layer (EEL) was introduced to boost triplet–triplet fusion (TTF). Second, new blue dopants with a higher orientation factor in the emitting layer were developed. Consequently, the external quantum efficiency (EQE) was increased up to 11.5% with Commission Internationale de l’Eclairage (CIE) 1931 color coordinates of (0.138, 0.092). The reported results may lead to EQEs that exceed 14% with fluorescent blue emitters.

We developed highly efficient fluorescent dopants for full‐color OLEDs. For blue, green and red OLEDs, current efficiencies of 8.7cd/A, 20.5 cd/A and 11.4 cd/A at 10mA/cm2 were achieved, respectively. Lifetime of the blue device was estimated to be 23,000hours at an initial luminance of 1,000 cd/m2. Moreover, long lifetime of 100,000 hours was estimated in the green and red devices. By the use of these dopants, we expect that a full‐color OLED display with the lifetime of 18,000 hours at a white luminance of 300 cd/m2 can be achieved.

The objective of this study is to show the effect of guide vane geometry on the performance. In order to overcome the disadvantages of vertical axis wind turbine, a straight-bladed vertical axis wind turbine (S-VAWT) with a directed guide vane row has been proposed and tested by the authors. According to previous studies, it was clarified that the performance of the turbine can be improved by means of the directed guide vane row. However, the guide vane geometry of S-VAWT has not been optimized so far. In order to clarify the effect of guide vane geometry, the effects of setting angle and gap between rotor blade and guide vane on power coefficient and starting characteristic were investigated in the experiments. The experimental study of the proposed wind turbine was carried out by a wind tunnel. The wind tunnel with a diameter of 1.8m is open jet type. The wind velocity is 8 m/s in the experiments. The rotor has three straight blades with a profile of NACA0018 and a chord length of 100 mm, a diameter of 0.6 m and a blade height of 0.7 m. The guide vane row consists of 3 arc plates.

The relationship between molecular shape of fluorescent blue dopants (BDs) IntroductionSome companies have started mass production of OLED TVs or OLED lighting. One of the most critical issues for OLED application is the reduction of power consumption due to the revision of power consumption regulation by "Energy Star" program or other commissions. Regarding phosphorescent devices, the performance of red or green devices has been dramatically improved and started to be used in practical applications. On the other hand, pure blue phosphorescent material with long lifetime has not yet been found. Therefore the improvement of fluorescent pure blue performance has been continuously needed. In 2008, we developed a technology to enhance the efficiency of blue fluorescence, "Triplet-triplet fusion (TTF)", however the efficiency was not so high under 10% of EQE [1].Recently molecular orientation attracts much attention to promote high efficiency of OLED. Specific molecular structures which show horizontal orientation to a substrate has been reported [2]. In addition, specific host and dopant materials show molecular orientation in a blue fluorescence device and show high EQE in doped and un-doped emitting systems [3][4][5].The objective of this paper is to reveal the relationship between molecular orientation property of applicative fluorescent blue dopants (BDs) and EQE of OLEDs. We composed four kinds of different fluorescent blue dopants with different molecular shape (ovality) and examined the influence of molecular orientation of BDs on the efficiency improvement of OLEDs. We found that BDs with larger ovality bring larger orientation factor and higher EQE in blue OLEDs with "Efficiency enhancement layer (EEL)" to enhance TTF phenomenon. Furthermore, as a result of analyzing IVL characteristic, impedance spectroscopy and transient EL [6][7][8], it was clarified that the effect of the EQE improvement depends only on the orientation of BD because they showed almost same carrier balance and TTF efficiency.