Search

Efficient light extraction is a critical issue for improving the overall efficiency of organic light-emitting diodes (OLEDs). Improvements in OLED efficiency are studied via the introduction of photonic crystal (PC) layers, which are expected to enable versatile control of photons. We fabricate two-dimensional PC structures in organic and electrode layers, in which most light is confined, to extract the light in the waveguide mode. Improvements in OLED efficiency of 20 and 130% are observed in spectrally integrated intensity and the peak intensity of forward-propagating light, respectively, in comparison with samples without PCs. As the thickness of the organic layer is partially reduced, lower operating voltages are found not to degrade light-extraction efficiency. We can expect further improvement in the overall OLED efficiency by optimizing PC structure.

— We have used bis(8-quinolinolato)phenolato-aluminum complexes as emission-layer hosts in red-phosphorescent OLED devices. This enabled high-efficiency long-lived OLED devices with a simple device structure that does not require a hole-blocking layer. Devices with a red-phosphorescent dopant introduced into a noble bis(8-quinolinolato)phenolato-aluminum complex exhibited a high efficiency of 12 cd/A at CIE color coordinates (0.65, 035) and a long operating lifetime of 30,000 hours or more at an initial luminance of 700 cd/m2. Moreover, triplet-triplet annihilation was reduced in the devices because of the wide emission zone enabled by the complex and the short phosphorescent lifetime of the red-phosphorescent dopant. We have successfully incorporated these red-phosphorescent devices into commercial OLED displays.

We have developed high-efficiency, long-lived organic light-emitting diode (OLED) devices by introducing red phosphorescent dopants into bis(8-quinolinolato)phenolato-aluminum(III) complexes. The devices exhibited luminance efficiency of 12 cd/A at CIE color coordinates (0.65, 034). The luminance half-decay lifetime is expected to be over 30,000 hours at an initial luminance of 700 cd/m2. We have successfully incorporated these devices into commercial OLED displays.

Multilayer organic light-emitting devices with phosphorescent guest emitter, tris(2-phenylpyridine) iridium doped in a host 4,4′-N,N′-dicarbazol-biphenyl layer were prepared. The device with the 6.5 wt% guest emitter exhibited external quantum efficiency and power luminous efficiency of 13.7% and 38.3 lm/W, respectively at the luminance of 105 cd/m2 driven at the voltage of 4.0 V and current density of 0.215 mA/cm2. The half decay lifetime under continuous constant-current driving for the initial luminance of 500 cd/m2 was 170 h.

To understand the low lying excited states of trans-polyacetylene, optical properties were studied at room temperature on carefully prepared samples by measuring photocurrent (PC) and photovoltage excitation spectra as well as optical absorption and reflectance. The 1.4 eV PC peak, the appearance of which sensitively depends on the sample quality, is correlated with some additional absorption sticking to the intrinsic absorption edge. An enhancement of PC with Au-Al electrodes biased reversely was observed in excitation spectra between 1.5∼2.0 eV, indicating that the formation of excitons causes three reflection peaks in this spectral region.

The paper explains the phenomenon that the dynamic moduli of cohesive soil consolidated anisotropically depend on the strain history, through a series of triaxial vibration tests. First, by the deduction of constitutive relation for drained shear of clay, it is concluded that the difference of strain history between isotropic and anisotropic consolidation causes the characteristics of mechanical behavior of each soil. Then, the undrained vibratory test with the strain level of 10-4 indicates that the dynamic rigidity of K0-consolidated clays is as high as 1.5 times that of isotropically consolidated ones. The dependency of the dynamic rigidity on the confined stress and the void ratio is also investigated using the test results.

Background Elder abuse is a serious public health concern that increases the risks of negative health outcomes globally. It is well known that abuse in older adults is associated with depression; however, longitudinal studies investigating the causal relationship between these events are scarce. Because the cause precedes the result over time, the temporal relationships between abuse and depression should be verified from each direction. This longitudinal study therefore investigated and clarified whether depression causes or results from elder abuse among older Japanese adults. Methods Two longitudinal analyses were conducted using data derived from the Japan Gerontological Evaluation Study. The data were collected in 2010 and 2013 through a mail survey of 1737 people (983 females, 754 males) across Japan. Results Of those who did not experience abuse in 2010, 38 (5.0%) males and 53 (5.4%) females newly experienced abuse in 2013. Among respondents who did not have depressive symptoms in 2010, 60 (8.0%) males and 61 (6.2%) females newly reported depressive symptoms in 2013. After adjusting for demographic factors in analysis 1, people who experienced abuse were 2.28-fold (95% confidence interval [CI] = 1.68-3.09) more likely to have depressive symptoms 3 years later than those who were not abused. In analysis 2, respondents who had mild or severe depression in 2010 were 2.23-fold (95% CI = 1.61-3.10) more likely to have experienced abuse after 3 years than those who did not have depression. Conclusions After adjusting for several demographic factors, the results showed that abuse can lead to depression and that depression can be a cause of abuse. Therefore, preventing abuse should be considered from both directions. Key messages Elder abuse could be a cause for depressive symptoms. Depressive symptoms could be a cause of elder abuse.

Polyacetylene film with aligned fibrils across the film thickness was synthesized using a liquid crystalline catalyst under a magnetic field. The morphology observed by an electron microscope was characteristic in the fibril thickness (no less than 1 µm in diameter) in addition to the fibril orientation. The presence of well developed fibrils across the film thickness suggests the possibility of intrafibrillar electric measurements.