Growth mechanism of thermally processed Cu(In,Ga)S2 precursors for printed Cu(In,Ga)(S,Se)2 solar cells

We investigate a process used for the selenisation of particle‐based precursors to prepare low‐cost Cu(In,Ga)(S,Se)₂ (CIGS) solar cells. It is suitable for high throughput with a short optimum selenisation duration of 3–5 min and employs a rapid thermal annealing system with elemental selenium vapour. Homogeneous crack‐free Cu(In,Ga)S₂ precursor films of up to 1 µm are obtained via doctor blading. The high selenium vapour pressure in the selenisation reaction chamber results in the formation of a compact Cu(In,Ga)(S,Se)₂ layer on top of a carbon‐rich underlayer. In order to investigate the phase development in the film, the selenisation process was interrupted at different stages and the samples were monitored via XRD and surface‐sensitive Raman measurements. We find the formation of a polycrystalline Cu(In,Ga)Se₂ phase already after 1 s at the target temperature of 550 °C. Furthermore, the effect of initial precursor thickness on solar cell parameters is discussed. Complete solar cells are prepared by conventional methods, leading to conversion efficiencies well above 8%. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Dynamics of the swollen lamellar phase

We investigate the dynamical behavior of lamellar phases in ternary amphiphilic systems of water, oil and amphiphile. The interaction between the amphiphilic monolayers is described by the steric interaction due to thermal fluctuations for uncharged, and by electrostatic interactions for charged systems. The dynamics of the system is determined by the hydrodynamics of the fluid layers. The basic parameters of our model are the viscosities of the two solvents, the average thicknesses of the oil and water layers, and the bending rigidity. The model allows to consider different monolayer interactions across the oil and water layers. Relaxation rates are calculated for arbitrary wave vectors parallel and perpendicular to the average monolayer plane. We find that there is a quite complex crossover behavior from a law for small parallel wave vectors to a law for large . We discuss the relevance of our result for the interpretation of dynamic light-scattering and neutron-spin-echo experiments for these systems. Received 7 December 1999     

Structure and Morphology of a Polyether/Polyacrylate Semi-interpenetrating Polymer Network

In this study NMR and DSC are used to probe the structure, thermal characteristics and morphology of a network formed from a diepoxide/acrylate system. Separate chemistries are employed to polymerize the diepoxide and acrylate components. The cationic polymerization of the diepoxide exhibits excellent selectivity in producing a crosslinked polyether network without affecting the acrylate monomer. Subsequent photoinitiated free-radical polymerization of the acrylate produces a phase separated, semi-interpenetrating polymer network (SIPN).This revised version was published online in November 2005 with corrections to the Cover Date.     

Structure and Stability of TaON Polymorphs

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.     

pH Dependence of T1 for 13C-Labelled Small Molecules Commonly Used for Hyperpolarized Magnetic Resonance Imaging

Hyperpolarization is a method to enhance the nuclear magnetic resonance signal by up to five orders of magnitude. However, the hyperpolarized (HP) state is transient and decays with the spin-lattice relaxation time (T₁), which is on the order of a few tens of seconds. Here, we analyzed the pH-dependence of T₁ for commonly used HP ¹³C-labelled small molecules such as acetate, alanine, fumarate, lactate, pyruvate, urea and zymonic acid. For instance, the T₁ of HP pyruvate is about 2.5 fold smaller at acidic pH (25 s, pH 1.7, B₀=1 T) compared to pH close to physiological conditions (66 s, pH 7.3, B₀=1 T). Our data shows that increasing hydronium ion concentrations shorten the T₁ of protonated carboxylic acids of most of the analyzed molecules except lactate. Furthermore it suggests that intermolecular hydrogen bonding at low pH can contribute to this T₁ shortening. In addition, enhanced proton exchange and chemical reactions at the pK_a appear to be detrimental for the HP-state.     

Development of homogeneous polyamine organocatalyst for the synthesis of 2-aryl-substituted benzimidazole and benzoxazole derivatives

A new polyamine was prepared by the ring opening polymerization of epichlorohydrin and properly characterized. The catalytic property of the prepared polymer was assessed by synthesizing 2-aryl-substituted benzimidazole and benzoxazole derivatives by the conjugation of o-phenylenediamine/o-aminophenol with various aromatic aldehydes in the presence of atmospheric oxygen. Significant attributes of the present synthesis include short reaction time, good to excellent yield, high purity, easy reusability, and room temperature reaction. The reaction was carried out in the absence of any metal catalyst and other cooxidants.     

Thermogravimetric analysis of calcium montmorillonite treated with hexamethylene diisocyanate

The product of the reaction between calcium montmorillonite and hexamethylene diisocyanate in acetone, catalyzed with dibutyltin dilaurate, was studied by thermogravimetry to determine the amount of polymer produced. The method developed to determine polymer content in the clay possessed excellent accuracy and precision, and produced more consistent results than traditional gravimetric methods.This research originated as a portion of the author's Master's degree research undertaken at California State Polytechnic University Pomona, and conducted at the Getty Conservation Institute (GCI). The author is indebted to the following colleagues at the GCI for providing advice and direction: Neville Agnew, Charles Selwitz, Dusan Stulik, James Druzik, David Scott and William Ginell. Consolidated adobe samples were prepared at the GCI by Richard Coffman, and by Dr. Michael Geis, department of Chemistry, Loyola University. Much valuable information and technical assistance was provided by Dr. Hans Wiedemann and Genia Paul, both of Mettler Instrument Corporation.     

Elastic electron deuteron scattering on a tensor polarized solid ND3 target

Elastic electron deuteron scattering has been measured at the Bonn 2.5 GeV electron-synchrotron using a tensor polarized ND₃ target. The scattered electrons and deuterons were detected in coincidence by two magnetic spectrometers. Data were taken at an average value of four momentum transfer ofQ ²=0.495 (GeV/c)² in order to separate the electric monopole and quadrupole form factors of the deuteron. To have a sufficient control of systematic effects, both polarized and unpolarized cross sections were measured with an identical experimental set up. In the ratioR _EXP=dσ_pol/dσ_unp systematic effects are expected to cancel. This ratioR _EXP is related to the theoretical polarized cross section d dσ _T where the spin quantization axis for the deuterons is orientated in the ed-scattering plane, perpendicular to the virtual photon direction. Our final result for the corresponding recoil tensor polarization ist ₂₀=?2.01±1.13.     

Cooperative effects in restricted rotations of aryl groups in 2,4,6,8-tetraary-3,7-diazabicyclo[3.3.1]nonanes and related systems

The free energies, enthalpies and entropies of activation for the rotation of the aryl groups in the N,N′-dimethyl and N,N′-dichloro derivatives of rel-(2R,4S,6S,8R)-2,4,6,8-tetrakisaryl-3,7-diazabicyclo[3.3.1]nonanes have been determined and compared with related tricyclic systems which cannot undergo chair-to-boat conformational changes. It is concluded on the basis of the large, negative value of ΔS³ for rotation of the 2(4) aryl group that this rotational process is correlated with rotation of the 8(6) aryl group. The 8(6) aryl group can however rotate independently of the 2(4)-aryl group. The usefulness of the entropies of activation as a criterion for cooperative rotation of groups is briefly discussed.