We report magnetic susceptibility ( X B ~ i n (T)) , and magnetic scattering (neutron) studies for the superconducting complex LalBazCu307 and the insulating complex Pr1BazCu307-6. The magnetic susceptibility and scattering measurements on the compound Pr1Ba2C~307-~ show no sign of magnetic ordering. For the LalBazCu30.r-6 samples we observe only a small change in the Pauli susceptibility and a decrease in the Curie-constant as Tc of the samples is increased. In compounds of the generic form RBa&u3o7-6 of which trivalent R ion is used from among yttrium and the rare earths [I, 21, it has been found that Tc for superconductivity is not substantially altered by the presence of the rare earth. The exceptions to this rule are the Pr, Tb and Ce compounds, where the serniconducting behavior of these compounds [3] has been attributed to the valency of the rare earth ions. The incorporation of Pr into the Y-Ba-Cu-0 complex leads to drastic decrease in the transition temperature [4] whereas Ce phase segregates into BaCeO3 [5]. This behavior is of particular interest, with respect to the magnetic ordering which occurs in the CuO planes [6, 71; the reason being that if Pr (in the compound PrlBazCu307-6) were in a +4 valence, then a simple valence counting argument would show if S = 0, then the most of the cu ions would be in a +2 valence state. The direct observation of (antiferromagnetic) ordering using susceptibility techniques however is difficult due to the magnetic contribution of the Pr ion. The magnetic ordering of the Cu spins in the CuO planes can be studied using elastic neutron scattering techniques. The LalBazCu307-6 system has been the subject of extensive study by our group; Tc of this system of compounds has not been as high as that reported for the corresponding YrBazCusO;.-s case I7]. The role of disorder of La/Ba has already been established to be a major reason for the low Tc's in this system [ti, 91, but until now no correlation has been made, of the interplay between magnetism and disorder. Lo, Ba2Cu,0,-, O 4 j

We present results on the characterization of a highly efficient CZTSSe solar cell fabricated using a solution-based process, aiming to gain a better understanding of its efficiency-limiting causes. Under red light illumination, we observed a red-kink in the current-density versus voltage (J-V) curve, likely due to a persistent photoconductivity in the buffer layer. Temperature-dependent J-V analysis suggests that interface recombination is the dominant loss mechanism. Defect analysis using admittance spectroscopy (AS) shows a single bulk defect level at ~63 meV and may be attributed to copper vacancy (VCu). The carrier concentration of the device determined using drive-level capacitance profiling (DLCP) is ~2.5×1016 cm-3.

A new solution-based method to fabricate Cu(2)ZnSn(S,Se)(4) (CZTSSe) thin films is presented. Binary and ternary chalcogenide nanoparticles were synthesized and used as precursors to form CZTSSe thin films. The composition of the CZTSSe films can be easily controlled by adjusting the ratio of the nanoparticles used. The effect of compositional adjustment on device performance is illustrated. Laboratory-scale photovoltaic cells with 8.5% total-area efficiency (or 9.6% active-area efficiency) were demonstrated without anti-reflective coatings. Material characterization data revealed the formation of a bilayer microstructure during thermal processing and suggested a path forward on device improvement.

Solution-based Cu2ZnSn(S,Se)(4) (CZTSSe) thin film deposition routes focusing on chemistries with attractive scalability and handling characteristics, while delivering high efficiency devices are promising technologies for low-cost solar cells. In this paper we describe a new approach for the fabrication of CZTSSe thin films using inks comprised of mixtures of binary and ternary metal-chalcogenide nanocrystals dispersed in simple organic solvents. The resulting blended inks can be coated under ambient conditions to give precursor films which are in turn converted to device-quality CZTSSe absorbers via thermal annealing in a selenium atmosphere. Using this approach we have demonstrated CZTSSe solar cells with total area efficiencies in excess of 8.5% (or 9.6% per active area) under 1 Sun AM1.5 illumination.

We report far infrared reflectance measurements of RBa2Cu3Ox, where R-Y, Er and Nd and 6<×<7 for YBa2Cu3Ox. Based on these measurements we assign the observed phonon features. In particular, one vibration is clearly identified as an R vibration, while the lowest energy mode (near 151 cm-1) is associated with the linear Cu-O chains.

We have examined the adsorption of simple alcohols and 2-propanamine on H-ZSM-5 zeolites with Si/Al2 ratios between 38 and 520. Thermogravimetric analysis (TGA) demonstrated that most of the molecules display a clearly defined adsorption state corresponding to a coverage of one molecule per Al site. Temperature programmed desorption (TPD) and transmission infrared spectroscopy results for each of the molecules in this 1:1 adsorption state are consistent with adsorption being due to the transfer of a proton from the zeolite to the adsorbed molecule. These results provide additional evidence that carefully prepared H-ZSM-5 is a Bronsted acid, with one acid site per framework Al atom, in which all of the acid sites are identical in strength.

Previous efforts aimed at modeling solar cell bowing due to the aluminum back surface field (BSF) have focused on relatively simple two or three layer models. This paper will outline the effort to develop a more sophisticated finite element (FE) model approach. This approach is superior to previous modeling efforts since it allows a more accurate representation of the cell structure and can handle complex geometry like the front surface grid and silver bus bars. The first section of the paper will highlight previous modeling efforts touching on the strengths and weaknesses of the various approaches. The second section focuses on the unique measurement techniques used to quantify actual solar cell bowing. The final section of the paper will concentrate on the model details and the use of the model to gain insight into how the various layer thicknesses (silicon, eutectic, aluminum, etc.) and cell geometry impact cell bowing.

Submitted for the MAR06 Meeting of The American Physical Society Structure at low temperature of oxygen isotope exchanged La1.8875Sr0.1125CuO4 A. R. MOODENBAUGH, D. E. COX, T. VOGT, B. NOHEDA, Brookhaven National Lab., M. K. CRAWFORD, E. M. MCCARRON, W. E. FARNETH, Dupont — The crystal structures at low temperatures of oxygen isotope-exchanged pairs of La1.8875Sr0.1125CuO4 were examined using high resolution synchrotron powder x-ray diffraction at NSLS X7A. This study was designed to examine the possibility that small structural differences might contribute to the observed superconducting isotope effects. The x-ray diffraction regions about the orthorhombic (200),(020) peaks of 16O and 18O isotope-exchanged pairs were studied in detail. There is no significant difference in orthorhombic lattice parameters at any temperature. A minority (∼10%) tetragonal (LTT) phase is also necessary to adequately account for the observed intensities at low temperatures. The fraction of LTT phase does not differ perceptibly with oxygen isotope exchange. We conclude, based on direct measurement of crystal structure at low temperatures, that the observed differences in superconductivity of oxygen isotope exchanged pairs are likely intrinsic effects. 1Research Supported by the U.S. Dept. of Energy Contract DE-AC02-98CH10886. A. R. Moodenbaugh Brookhaven National Lab. Date submitted: 30 Nov 2005 Electronic form version 1.4

L'invention concerne une pile a combustible comprenant une anode et une cathode immergees dans un electrolyte en presence d'un agent reducteur et d'un agent d'oxydation, ladite pile etant caracterisee en ce que tous ses elements communiquent librement les uns avec les autres et qu'il n'y a pas de membrane ou tout autre separateur entre l'anode et la cathode.

Atomic force microscopy (AFM) was used to study the surface structure and the photoreactivity of individual TiO 2 crystallites with high spatial resolution. The photochemical reduction of Ag and Au salts to metals in aqueous solutions was used to generate Ag/TiO 2 and Au/TiO 2 catalysts with uniform, nanoscale metal particles. The effect of the titania crystal structure on the photodeposition was examined using rutile and anatase TiO 2 crystallites. AFM can probe in situ both the metal deposition reactions and the surface structure of metal-decorated oxide particles. The distribution of the metal particles on individual TiO 2 crystallites was not random. The concentration of metal particles was higher on certain crystallographic orientations, grain boundaries and surface defects. These methods can be used to define structure/activity relationships and investigate potential methods for manipulating the performance of TiO 2 -based catalysts and photocatalysts.

We have developed a new class of solid acid catalyst, a Nafion resin/silica nanocomposite, which effectively catalyzes a wide range of industrially important reactions. These include olefin isomerizations, alkylations, acylations, oligomerizations, the Fries reaction, esterifications and benzylations. We have found that the catalytic activity of these materials is dependent upon the synthetic conditions. The catalytic activity is related to the extent of dispersion of the Nafion resin acid groups within the porous silica framework. The use of an in situ sol-gel technique is preferred over infiltration of a pre-formed support with a Nafion solution. Here we show how we can use solid state NMR, electron microscopy and temperature programmed desorption to elucidate the chemical environment and dispersion of the acid sites. We also show how the microstructure may be tailored depending upon the synthetic conditions. This is a rare example of tuning catalyst activity for particular reactions. In the case of alkylations (such as formation of linear alkyl benzenes), transalkylation and acylation chemistry, the activities are increased several fold using a catalyst in which the Nafion resin is slightly aggregated. A highly dispersed form of the Nafion resin within the silica is preferred for dimerization chemistry. In the case of olefin isomerization chemistry, variations in the Nafion resin dispersion have little effect upon catalytic activity. A correlation of microstructure-processing-properties is described.

In this paper we describe an experimental procedure that can be used to study the photoreduction of metal ions on the surfaces of individual TiO2 particles. The submicrometer-sized particles are isolated on porous membranes, characterized by atomic force microscopy (AFM), removed from the microscope, exposed to AgNO3 solution and light, and reimaged. Photoreduction of Ag+ produces 5−50 nm particles of Ag0 distributed over the surfaces of the TiO2 particle. This procedure allows the spatial distribution of the chemical reactivity of particle surfaces to be mapped at the nanometer scale resolution of the atomic force microscope. Using different excitation wavelengths (366, 400 and ∼600 nm), we demonstrate by AFM that the photoreduction of Ag on single anatase or rutile particles is consistent with the differences in the band gaps of the bulk samples. We also show that the Ag0 particles are not uniformly distributed over the TiO2 crystallite surfaces implying that a closer study of the unreacted particle sur...

The photochemistry of oriented rutile surfaces has been examined using the photoreduction of Ag+ to Ag metal from an aqueous solution onto the TiO2 surfaces. The photochemical reaction rates and quantum yields of rutile films were found to be a function of the orientation of the rutile surface. The (100) and (110) rutile orientations have lower photoreduction rates than the (101), (111), and (001). This dependence of the photochemical reaction rates on film surface orientation is observed over a range of light intensities, illumination wavelengths, and film thicknesses. Atomic force microscopy has been used to characterize the morphologies of the film surfaces and the photoreduced Ag at these surfaces. Several properties of rutile, such as the surface morphology, surface chemistry, space charge phenomena, and charge transport, are discussed in relation to their possible contributions to the orientation dependence of the photochemistry on the rutile films.