Evaluating the effect of dislocation on the photovoltaic performance of metamorphic tandem solar cells

The photovoltaic conversion efficiency for monolithic GaInP/GaInAs/Ge triple-junction cell with various bandgap combination (300 suns, AM1.5d) was theoretically calculated. An impressive improvement on conversion efficiency was observed for a bandgap combination of 1.708, 1.194, and 0.67 eV. A theoretical investigation was carried out on the effect of dislocation on the metamorphic structure's efficiency by regarding dislocation as minority-carrier recombination center. The results showed that only when dislocation density was less than 1.6x10(6) cm(-2), can this metamorphic combination exhibit its efficiency advantage over the fully-matched combination. In addition, we also briefly evaluated the lattice misfit dependence of the dislocation density for a group of metamorphic triple-junction system, and used it as guidance for the choice of the proper cell structure.

Density functional study on the reaction mechanism of palladium-catalyzed addition of cyanoboranes to Alkynes

The B3LYP hybrid density functional method has been carried Out to Study theoretically the mechanisin of Pd(0)-catalyzed alkyne cyanoboration reaction. Both the intermolecular and intramolecular alkyne cyanoboration reactions were studied. For each reaction, three paths were proposed. In path A of each reaction, the first step is B-CN bond oxidative addition to bisphosphine complex Pd(PH3)(2), in path B of each reaction, the first step is alkyne coordination to bisphosphine complex Pd(PH3)2, and in path C of each reaction, the first step is the PH3 dissociation front Pd(PH3)2 to form monophosphine complex Pd(PH3) For both reactions, path B is favored.

Novel Sulfonated Polyimide Ionomers by Incorporating Pyridine Functional Group in the Polymer Backbone

A series of sulfonated polyimides (SPIs) containing pyridine ring in the polymer backbone were synthesized by the polycondensation of 1,4,5,8-naphthalene-tetracarboxylic dianhydride (NTDA), 5-(2,6-bis(4-arninophenyl)pyridin-4-yl)-2-methoxy benzene sulfonic acid (SDAM), and 4,4'-diaminodiphenyl ether (ODA). Flexible, transparent, and tough membranes were obtained. Property study revealed that all the membranes displayed high thermal stability with the desulfonation and decomposition temperature higher than 290 and 540 degrees C, respectively, as well as good mechanical property with Young's modulus larger than 1.0 GPa, maximum strength (MS) on a scale of 60-80 MPa, and elongation at break (EB) ranged from 41.79 to 75.17%.

Density functional study of the second row transition metal dimers

Equilibrium geometries, vibrational frequencies and dissociation energies of the second row transition metal dimers (from Y-2 to Cd-2 except Tc-2) ere studied by use of density functional methods B3LYP, BLYP, B3PW91, BHLYP, BP86, B3P86, SVWN, MPW1PW91 and PBE1PBE. The accuracy DFT methods is found to be highly dependent on the functional employed, in particular for vibrational frequency and dissociation energy. In most cases, the predicted bond distance is in general agreement with experiment and previous theoretical results. For van der Waals dimer Cd-2, B3LYP and BLYP have excellent performance in predicting the bond distance. For Ag-2, all density functional methods used in this study perform well in producing the bond distance, vibrational frequency and dissociation energy.

Zooplankton functional groups on the continental shelf of the yellow sea

Zooplankton plays a vital role in marine ecosystems. Variations in the zooplankton species composition, biomass, and secondary production will change the structure and function of the ecosystem. How to describe this process and make it easier to be modeled in the Yellow Sea ecosystem is the main purpose of this paper. The zooplankton functional groups approach, which is considered a good method of linking the structure of food webs and the energy flow in the ecosystems, is used to describe the main contributors of secondary produciton of the Yellow Sea ecosystem. The zooplankton can be classified into six functional groups: giant crustaceans, large copepods, small copepods, chaetognaths, medusae, and salps. The giant crustaceans, large copepods, and small copepods groups, which are the main food resources for fish, are defined depending on the size spectrum. Medusae and chaetognaths are the two gelatinous carnivorous groups, which compete with fish for food. The salps group, acting as passive filter-feeders, competes with other species feeding on phytoplankton, but their energy could not be efficiently transferred to higher trophic levels. From the viewpoint of biomass, which is the basis of the food web, and feeding activities, the contributions of each functional group to the ecosystem were evaluated; the seasonal variations, geographical distribution patterns, and species composition of each functional group were analyzed. The average zooplankton biomass was 2.1 g dry wt m(-2) in spring, to which the giant crustaceans, large copepods, and small copepods contributed 19, 44, and 26%, respectively. High biomasses of the large copepods and small copepods were distributed at the coastal waters, while the giant crustaceans were mainly located at offshore area. In summer, the mean biomass was 3.1 g dry wt m(-2), which was mostly contributed by the giant crustaceans (73%), and high biomasses of the giant crustaceans, large copepods, and small copepods were all distributed in the central part of the Yellow Sea. During autumn, the mean biomass was 1.8 g dry wt m(-2), which was similarly constituted by the giant crustaceans, large copepods, and small copepods (36, 33, and 23%, respectively), and high biomasses of the giant crustaceans and large copepods occurred in the central part of the Yellow Sea, while the small copepods were mainly located at offshore stations. The giant crustaceans and large copepods dominated the zooplankton biomass (2.9 g dry wt m(-2)) in winter, contributing respectively 57 and 27%, and they, as well as the small copepods, were all mainly located in the central part of the Yellow Sea. The chaetognaths group was mainly located in the northern part of the Yellow Sea during all seasons, but contributed less to the biomass compared with the other groups. The medusae and salps groups were distributed unevenly, with sporadic dynamics, mainly along the coastline and at the northern part of the Yellow Sea. No more than 10 species belonging to the respective functional groups dominated the zooplankton biomass and controlled the dynamics of the zooplankton community. The clear picture of the seasonal and spatial variations of each zooplankton functional group makes the complicated Yellow Sea ecosystem easier to be understood and modeled. (C) 2010 Elsevier Ltd. All rights reserved.

Application of the compatibility relationship(1) in seeking a functional relationship among species' equilibrium quantities in complex systems

A new algorithm, representing an important advance in determination of the functional relationship, is first reported here. The algorithm is very useful and convenient for analyzing the incorporation of impurities. To show how the algorithm works, two early and well-known vapor phase epitaxy (VPE) experiments-Ashen's (Ashen, D. J.; Dean, P. J.; Hurle, D. T. J.; Mullin, J. B.; Royle, A.; White, A. M. Gallium Arsenide and Related Compounds, Institute of Physics Conference Series 24, 1974; Institute of Physics: London, 1975; p 229.), involving the doping of silicon and DiLorenzo's (DiLorenzo, J. V. J. Cryst. Growth 1972, 17, 189.), involving the mole fraction effect-are calculated to find the functional relationship between the Si contamination and the partial pressure of HCl. The calculated curves agree with the experimental results. A conclusion that the calculated values are greater than the true values has been drawn.

Toward high-performance polymer solar cells: The importance of morphology control

Polymer solar cells have the potential to become a major electrical power generating tool in the 21st century. R&D endeavors are focusing on continuous roll-to-roll printing of polymeric or organic compounds from solution-like newspapers-to produce flexible and lightweight devices at low cost. It is recognized, though, that besides the functional properties of the compounds the organization of structures on the nanometer level-forced and controlled mainly by the processing conditions applied-determines the performance of state-of-the-art polymer solar cells. In such devices the photoactive layer is composed of at least two functional materials that form nanoscale interpenetrating phases with specific functionalities, a so-called bulk heterojunction. In this perspective article, our current knowledge on the main factors determining the morphology formation and evolution is introduced, and gaps of our understanding on nanoscale structure-property relations in the field of high-performance polymer solar cells are addressed. Finally, promising routes toward formation of tailored morphologies are presented.

Feasibility of Protein a for the Oriented Immobilization of Immunoglobulin on Silicon Surface for a Biosensor with Imaging Ellipsometry

The feasibility of using protein A to immobilize antibody on silicon surface for a biosensor with imaging ellipsometry was presented in this study. The amount of human IgG bound with anti-IgG immobilized by the protein A on silicon surface was much more than that bound with anti-IgG immobilized by physical adsorption. The result indicated that the protein A could be used to immobilize antibody molecules in a highly oriented manner and maintain antibody molecular functional configuration on the silicon surface. High reproducibility of the amount of antibody immobilization and homogenous antibody adsorption layer on surfaces could be obtained by this immobilization method. Imaging ellipsometry has been proven to be a fast and reliable detection method and sensitive enough to detect small changes in a molecular monolayer level. The combination of imaging ellipsometry and surface modification with protein A has the potential to be further developed into an efficient immunoassay protein chip.