UV/ozone‐treated WS2 hole‐extraction layer in organic photovoltaic cells

WS₂ nanosheets obtained through a simple sonication exfoliation method are employed as a hole‐extraction layer to improve the efficiency of organic photovoltaic cells (OPVs). A reduction in the wavenumber difference in the Raman spectra, the appearance of a UV absorption peak, and atomic force microscopy images indicate that WS₂ nanosheets are formed through the sonication method. The power conversion efficiency (PCE) values of OPVs with and without untreated WS₂ layers are both 1.84%. After performing a UV‐ozone (UVO) treatment on the WS₂ surface for 15 min, the PCE increases to 2.4%. Synchrotron radiation photoelectron spectroscopy data show that the work function of WS₂ increases from 4.9 eV to 5.1 eV upon UVO treat‐ ment, suggesting that the increase in the PCE value is caused by the band alignment. Upon inserting poly(3,4‐ethylenedioxythiophene):poly(styrene‐sulfonate) (PEDOT: PSS) between the WS₂ and the active layer, the PCE value of the OPV increases to 3.07%, which is superior to that of the device employing only PEDOT:PSS (2.87%). Therefore, it is considered that the use of UVO‐treated WS₂ is able to improve the performance of OPV cells. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Convergence of an extragradient-type method for variational inequality with applications to optimal control problems

Numerical Algorithms - Our aim in this paper is to introduce an extragradient-type method for solving variational inequality with uniformly continuous pseudomonotone operator. The strong...     

Effects of Additives on the Laser-Initiated Polymerization of 1,6-Hexanediol Diacrylate

Polymerization exotherms of 1,6-hexanediol diacrylate (HDDA) were generated by a pulsed laser source and recorded on a modified differential scanning calorimeter. Several aromatic carbonyl-based photoinitiators were compared with respect to maximum rate and extent of polymerization in the absence and presence of oxygen. α-Cleavage photoinitiators were more efficient than the hydrogen-abstracting benzophenone. The addition of an amine to a photocleavable initiator improved the polymerization of HDDA under an inert atmosphere, whereas triarylphosphines under similar conditions were effective in reducing the air inhibition. This synergistic effect depends on the type and structure of the additive and the photoinitiator.

The use of benzophenone in combination with an α-cleavage photoinitiator showed no significant effect upon polymerization, while extra thermal energy imposed upon the system slightly improved the polymerization.     

Anomalous flow deflection at earth's low-Alfvén-Mach-Number bow shock

Earth's magnetosphere is an obstacle to the supersonic solar wind and the bow shock is formed in the front side of it. In ordinary hydrodynamics, the flow decelerated at the shock is diverted around the obstacle symmetrically about the Earth-Sun line, which is indeed observed in the magnetosheath most of the time. Here we show a case under a very low-density solar wind in which duskward flow was observed in the dawnside magnetosheath. A Rankine-Hugoniot test shows that the magnetic effect is crucial for this "wrong flow" to appear. A full three-dimensional magnetohydrodynamics (MHD) simulation of the situation confirming this interpretation and earlier simulations is also performed. It is illustrated that in addition to the "wrong flow" feature, various peculiar characteristics appear in the global picture of the MHD flow interaction with the obstacle.     

Mössbauer Studies of Core-Shell FeO/Fe3O4 Nanoparticles

Physics of the Solid State - FeO/Fe3O4 nanoparticles were synthesized by thermal decomposition. Electron microscopy revealed that these nanoparticles were of the core-shell type and had a spherical...     

Validation of Material Models in Grain Scale Simulation based on EBSD Experimental Data

A crystal plasticity model and a homogenization method are used to analyze the local and global mechanical behavior of a ferritic stainless steel. In the first step the material constants are determined based on tensile tests and used to simulate the local deformation behavior on the grain scale in the second step. For that 2D EBSD data are discretized by finite elements. The computed local grain reorientations of three different BCC slip systems are compared to experimental data at the state of 20% elongation. (© 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)