6-N,N-diphenylaminobenzofuran-derived pyran containing fluorescent dyes: a new class of high-brightness red-light-emitting dopants for OLED

Dye-doped organic light-emitting diode of ITO/alpha-NPB (70 nm)/Bebq(2)-1 (7 nm)/BCP (5 nm)/Bebq(2) (33 nm)/LiF (1 nm)/Al (150 nm) shows red electroluminescence with the efficiency of 2.9 cd/A at 100 cd/m(2) and maximum brightness of 62000 cd/m(2). The physical organic aspects of the current-induced fluorescent quenching effect are discussed. [structure: see text]     

Numerical study on a compact all-semiconductor-optical-amplifier Sagnac interferometer device

The nonlinear switching effect of an all-semiconductor-optical-amplifier Sagnac interferometer is numerically investigated. The device, stemming from the conventional nonlinear optical loop mirror made of fiber, has a much more compact size and a latency several hundred times smaller than the conventional ones. Numerical simulations are conducted for the case of cw signal operation. It is found that the nonlinear coupling in the MMIWA and the lateral field redistribution as well as the amplification of the signal through the loop structure contribute together to the nonlinear switching. Besides investigating the physical mechanism of the device, we vary relevant parameters to evaluate their influences on device performance. The numerical simulations show good agreement in trend with the experimental results.     

Optical effects of shadow masks on short circuit current of organic photovoltaic devices

In this paper, we have employed different shadow masks attached on top of organic photovoltaic (OPV) devices to study the optical effects of the former on the short circuit current (J(SC)). To rule out possible lateral electrical conduction and simplify the optical effects inside the device, a small-molecular heterojunction OPV device with a clear donor/acceptor interface was employed with a hole extraction layer exhibiting high resistance intentionally. Careful calibration with a shadow mask was employed. By attaching two layers of opaque masks in combination with a suitable holder design to shield the light from the edges and backside, the value of J(SC) approached that of the dark current, even under 1-sun radiation. With different illumination areas, we found that the photons illuminating the non-active region of the device contributed to 40% of the J(SC) by optical effect within the width of about 1 mm around the active region. When illuminating the non-active area with 12 mm to the active area, a 5.6 times improvement in the J(SC) was observed when the incident angle was 75°. With the introduction of a microstructured film onto the OPV device and an increase in the reflection from the non-active region, a 15% enhancement of the J(SC) compared to the control device was achieved.     

The unusual electrochemical and photophysical behavior of 2,2'-bis(1,3,4-oxadiazol-2-yl)biphenyls, effective electron transport hosts for phosphorescent organic light emitting diodes

The fluorescence and phosphorescence of 2,2'-bis(5-phenyl-1,3,4-oxadiazol-2-yl)biphenyl shows good spectral matching with the absorption spectra of the MLCT1 and MLCT3 transitions of Ir(ppy)3. The red-shift of the 0-0 band in the phosphorescence at 77 K is due to the intramolecular pi-pi interactions between the oxadiazole side chains. Maximum brightness of 43,000 cd/m2 with an efficiency of 26 cd/A at 200 cd/m2 was achieved when BOBP was used as the host material for Ir(ppy)3 in the PHOLED study. [structure: see text].     

Local measurement of the superfluid density in the pnictide superconductor Ba(Fe(1-x)Co(x))(2)As(2) across the superconducting dome

We measure the penetration depth λab(T) in Ba(Fe(1-x)Co(x))(2)As(2) using local techniques that do not average over the sample. The superfluid density ρs(T) ≡ 1/λab(T)2 has three main features. First, ρs (T = 0) falls sharply on the underdoped side of the dome. Second, λab(T) is flat at low T at optimal doping, indicating fully gapped superconductivity, but varies more strongly in underdoped and overdoped samples, consistent with either a power law or a small second gap. Third, ρs (T) varies steeply near Tc for optimal and underdoping. These observations are consistent with an interplay between magnetic and superconducting phases.