Group 1 coordination chains and hexagonal networks of host cyclotriveratrylene with halogenated monocarbaborane anions

Halogenated carbaborane ions [CB(11)H(6)X(6)](-) in which X=Cl or Br have been combined with the host molecule cyclotriveratrylene (CTV) and Group 1 metal cations to give crystalline materials. The complexes [Na(ctv)(H(2)O)(CB(11)H(6)X(6))](CF(3)CH(2)OH) feature chiral Na-CTV coordination chains with complexation of the [CB(11)H(6)X(6)](-) ion by the Na(+) ion, together with the CTV molecular cavity. The coordination chains are hydrogen bonded together to give a puckered two-dimensional hexagonal grid structure. [K(ctv)(CB(11)H(6)Cl(6))(CF(3)CH(2)OH)(0.5)] is essentially isostructural. Complexes [Rb(ctv)(CB(11)H(6)Br(6))(H(2)O)] and [Cs(ctv)(CB(11)H(6)X(6))(CH(3)CN)] are coordination polymers with related distorted hexagonal grid structures. Use of N,N'-dimethylformamide (DMF) as a solvent results in an entirely different type of assembly, with [Na(2)(dmf)(4)(H(2)O)(2)(ctv)][(dmf)(0.5)(ctv)][CB(11)H(6)Br(6)](2) showing unusual [Na-mu-(dmf)-Na] bridges, and once again forming a distorted hexagonal coordination polymer.     

Localization and characterization of annealing‐induced shunts in Ni‐plated monocrystalline silicon solar cells

The adhesion of Ni–Cu‐plated contacts requires annealing, which can lead to an electrical degradation of the solar cell. A combination of optical imaging methods and electron microscopical cross‐section analysis was used to investigate the annealing‐induced shunts on monocrystalline solar cells. The results show that Ni spikes cause the lowering of the pseudo fill factor and reveal that these nonlinear shunts show the same behavior as recombination active breakdown sites on multicrystalline silicon solar cells, including radiation of visible light while breakdown. Using reverse biased electroluminescence set‐up the shunts could be localized in top view with µm size lateral resolution. Subsequently, a cross‐section was prepared on a radiative breakdown spot. Advanced electron microscopic investigations reveal defect structures featuring nickel precipitates on the position of the light source. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

CuII‐Containing 1‐Aminocyclopropane Carboxylic Acid Oxidase Is an Efficient Stereospecific Diels–Alderase

In the context of developing ecofriendly chemistry, artificial enzymes are now considered as promising tools for synthesis. They are prepared in particular with the aim to catalyze reactions that are rarely, if ever, catalyzed by natural enzymes. We discovered that 1‐aminocyclopropane carboxylic acid oxidase reconstituted with Cu^II served as an efficient artificial Diels–Alderase. The kinetic parameters of the catalysis of the cycloaddition of cyclopentadiene and 2‐azachalcone were determined (K_M=230 μm , k_app=3 h^?1), which gave access to reaction conditions that provided quantitative yield and >99 % ee of the (1S,2R,3R,4R) product isomer. This unprecedented performance was rationalized by molecular modeling as only one docking pose of 2‐azachalcone was possible in the active site of the enzyme and this was the one that leads to the (1S,2R,3R,4R) product isomer.     

Electronic Structure and Interface Properties of a Model Molecule for Organic Solar Cells

We study the electronic structure of 4,7‐bis(5‐methylthiophen‐2‐yl)benzo[c][1,2,5]thiadiazole (MTBT) and its interface properties with gold using X‐ray photoemission spectroscopy (XPS), valence‐band ultraviolet photoemission spectroscopy (UPS), X‐ray absorption spectroscopy (XAS), as well as resonant photoemission (ResPES). MTBT can be regarded as a model molecule for PCPDTBT, a promising candidate for efficient bulk heterojunction solar cells. Almost no contribution of sulfur and only a weak contribution of nitrogen to the HOMO level is found. At the interface with gold, a strong chemical interaction between the sulfur of the benzothiadiazole and gold occurs, which may have consequences for interface properties in devices.     

Comparison of Laser Chemical Processing and LaserMicroJet for structuring and cutting silicon substrates

This paper deals with the development of a new cutting method for thin silicon solar wafers with liquid-jet-guided lasers (LaserMicroJet®, LMJ, and Laser Chemical Processing, LCP). Several laser systems with different wavelengths were tested to find the optimum laser system and processing parameters in terms of efficient material removal and deep laser cutting. Water and potassium hydroxide were used as carrier liquids to enhance laser ablation. The ablation efficiency was defined as a target parameter and experimentally determined by performing single laser grooves. It is demonstrated that the ablation process of LMJ is mainly affected by silicon melting and then removing by the liquid-jet momentum for single laser grooves. Best result for deep laser grooves is achieved if evaporation dominates the ablation process. Better surface quality referred to laser-induced crystalline damage is presented for a cut wafer with LMJ in comparison to a standard multiwire slurry saw. This shows a great potential of wafering with liquid-jet-guided lasers although no optimal liquid media was used.     

Surface‐Assisted Cyclodehydrogenation; Break the Symmetry,Enhance the Selectivity

Selectivity in chemical reactions is a major objective in industrial processes to minimize spurious byproducts and to save scarce resources. In homogeneous catalysis the most important factor which determines selectivity is structural symmetry. However, a transfer of the symmetry concept to heterogeneous catalysis still requires a detailed comprehension of the underlying processes. Here, we investigate a ring‐closing reaction in surface‐confined meso‐substituted porphyrin molecules by scanning tunneling microscopy, temperature‐programmed desorption, and computational modeling. The identification of reaction intermediates enables us to analyze the reaction pathway and to conclude that the symmetry of the porphyrin core is of pivotal importance regarding product yields.     

Simulation supported description of the local doping formation using laser chemical processing (LCP)

We present an enhanced model to describe the physics of laser chemical processing (LCP), a liquid jet guided laser technique, for local doping processes applied to crystalline silicon solar cells. The main improvement of the numerical model is the consideration of the inhomogeneous laser light intensity profile within the liquid jet cross section. Measurements of the intensity profile show local superelevations of up to factor five compared to the average intensity. A measured intensity profile was implemented into the numerical model and yields good agreement between simulated and measured dopant distributions. Inhomogeneities of the spatial dopant distribution are observed and their impact on LCP line scans for producing doped lines is investigated with respect to solar cell manufacturing.     

Lithiumphthalocyanine: Synthese,Eigenschaften und Kristallstruktur von Bis(triphenylphosphin)iminiumphthalocyaninatolithaten mit verschiedenen Konformationen des Kations

Lithiumphthalocyanines: Synthesis, Properties, and Crystal Structure of Bis(triphenylphosphine)iminiumphthalocyaninatolithates with Different Conformations of the Cation Reaction of tri(n-dodecyl)n-butylammoniumphthalocyaninatolithate, (TDBA)[LiPc^2?] with bis(triphenylphosphin)iminiumbromide, (PNP)Br in dichloromethane yields (PNP)[LiPc^2?]. It crystallizes in the triclinic space group P1 as dichloromethane solvate ( 1 ) and in the monoclinic space group P2₁/n as hydrate ( 2 ). The crystal structures of ( 1 ) and ( 2 ) are reported. Each salt contains two crystallographically slightly different discrete [LiPc^2?]^? anions, in which the square-planar coordinated Li⁺ cation is centered within the planar Pc^2? ligand (D_av.(Li? N_iso) = 1.945 Å). There are three different conformations for the (PNP) cation: ( 1 ) only contains the bent conformer (d_av.(P? N) = 1.575 Å; φ(P? N? P) = 140.8°), while in ( 2 ) an hybrid (d_av.(P? N) = 1.562 Å; φ(P? N? P) = 158.1°) and the linear conformer (d_av.(P? N) = 1.547 Å; φ(P? N? P) = 176.8°) are present. The very soluble, blue-green salts melt at 265°C without decomposition. In accordance with cyclovoltammetric data thin films of (PNP)[LiPc^2?] are oxidized by NO₂ or Br₂ to yield brown violet [LiPc^?]. The electronic absorption spectra and the vibrational spectra are discussed.