Laser machined macro and micro structures on glass for enhanced light trapping in solar cells

In order to increase the efficiency of solar cell modules it is necessary to make the optimum use of light incident upon them. Much research has been done on improving light absorption through front surface texturisation and light trapping schemes. Laser light is commonly used in industry for various applications including marking and texturisation. By controlling laser parameters, it is possible to tailor macro and micro structures in most materials. The CO₂ laser used in this investigation emits radiation at 10.6 μm with the ability to pulse in the micro-second range. The laser was used to ablate grooved textures in the fused quartz material, used in this study as the light trapping medium, following which an analysis of the effects of the laser parameters on the texture geometry and surface morphology was performed through a combination of cross sectioning and scanning electron microscopy. Transmission through the textured glass was improved for most samples after acid etching. The light trapping effects of the best performing textures were analysed by investigating the effects on a silicon solar cell’s performance at varying angles of incidence. Results indicated a significant increase in light trapping when light was incident at acute angles. For an angle of incidence of 10^° a relative increase in efficiency of up to 51 % was observed.     

Randomly Pk-decomposable graphs

A graph $G$ is $H$-decomposable if it can be expressed as an edge-disjoint union of subgraphs, each subgraph isomorphic to $H$. If $G$ has the additional property that every $H$-decomposable subgraph of $G$ is part of an $H$-decomposition of $G$, then $G$ is randomly $H$-decomposable. Using computer assistance, we provide in this paper a characterization of randomly path-decomposable graphs for paths of length 11 or less. We also prove the following two results: (1) With one small exception, randomly $P_k$-decomposable graphs with a vertex of odd degree do not contain a $P_{k+1}$-subgraph, (2) When the edges of a $P_k$-subgraph are deleted from a connected randomly $P_k$-decomposable graph, the resulting graph has at most one nontrivial component.     

The reactions of [Fe(CO)5-n(CNAr)n] (n = 1 or 2; Ar = aryl) with dicyclopentadiene

Although [Fe(CO)₃(CNAr)₂] complexes fail to react with dicyclopentadiene at 140°C, under the same conditions [Fe(CO)₄(CNAr)] complexes give high yields of [Fe₂(η-C₅H₅(CO)₃(CNAr)] and [Fe₂(η-C₅H₅)₂(CO)₂-(CNAr)₂], with the product ratios depending very much on the aryl group (Ar).     

A Unified Approach to Couple Aromatic Heteronucleophiles to Azines and Pharmaceuticals

Coupling aromatic heteronucleophiles to arenes is a common way to assemble drug‐like molecules. Many methods operate via nucleophiles intercepting organometallic intermediates, via Pd‐, Cu‐, and Ni‐catalysis, that facilitate carbon‐heteroatom bond formation and a variety of protocols. We present an alternative, unified strategy where phosphonium salts can replicate the behavior of organometallic intermediates. Under a narrow set of reaction conditions, a variety of aromatic heteronucleophile classes can be coupled to pyridines and diazines that are often problematic in metal‐catalyzed couplings, such as where (pseudo)halide precursors are unavailable in complex structures with multiple polar functional groups.     

Derivations, isomorphisms, and second cohomology of generalized Witt algebras

Generalized Witt algebras, over a field of characteristic , were defined by Kawamoto about 12 years ago. Using different notations from Kawamoto's, we give an essentially equivalent definition of generalized Witt algebras over , where the ingredients are an abelian group , a vector space over , and a map which is linear in the first variable and additive in the second one. In this paper, the derivations of any generalized Witt algebra
, with the right kernel of being , are explicitly described; the isomorphisms between any two simple generalized Witt algebras are completely determined; and the second cohomology group for any simple generalized Witt algebra is computed. The derivations, the automorphisms and the second cohomology groups of some special generalized Witt algebras have been studied by several other authors as indicated in the references.

     

The use of cationic surfactants to control the structure of zinc oxide films prepared by chemical vapour deposition

This paper describes a powerful and versatile new method for controlling the structure of zinc oxide thin films prepared by aerosol assisted chemical vapour deposition, based on the use of a common surfactant. The technique combines the benefits of solution and vapour based methods and leads to high quality morphologically-defined and orientated thin films.