Efficient nanotextured black silicon solar cells passivated by an Al2O3 layer are demonstrated. The broadband antireflection of the nanotextured black silicon solar cells was provided by fabricating vertically aligned silicon nanowire (SiNW) arrays on the n(+) emitter. A highly conformal Al2O3 layer was deposited upon the SiNW arrays by the thermal atomic layer deposition (ALD) based on the multiple pulses scheme. The nanotextured black silicon wafer covered with the Al2O3 layer exhibited a low total reflectance of ∼1.5% in a broad spectrum from 400 to 800 nm. The Al2O3 passivation layer also contributes to the suppressed surface recombination, which was explored in terms of the chemical and field-effect passivation effects. An 8% increment of short-circuit current density and 10.3% enhancement of efficiency were achieved due to the ALD Al2O3 surface passivation and forming gas annealing. A high efficiency up to 18.2% was realized in the ALD Al2O3-passivated nanotextured black silicon solar cells.

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The syntheses, structures, and physical properties of a full series of benzannulated tetraphenylenes are reported. The palladium-catalyzed annulation of tetraiodo-substituted 2,3,6,7,10,11,14,15-octamethyltetraphenylene with insufficient di(4-anisyl)ethyne yielded a mixture of per-substituted [8]circulene and its non-planar fragments, including mono-, para-di-, ortho-di-, and triannulated products. Their structures were unambiguously verified by X-ray crystallography. Successive benzannulations significantly affect the molecular geometries, dynamic behaviors, and physical properties of the compounds. In this series of compounds, [8]circulene is the most strained one, as reflected by the significant deplanarization of the phenanthrene moieties (ca. 63° in the bay region) and the fact that it has the highest strain energy (120.6 kcal mol(-1) ). The dynamic behaviors of these compounds were examined both experimentally and theoretically. The ring flipping of per-substituted [8]circulene is confirmed to proceed through pseudorotation with a barrier of around 21 kcal mol(-1) , whereas its non-planar fragments require much more energy for the ring inversion. The photophysical and electrochemical properties of the investigated compounds depend strongly on the extent of efficient π conjugation. The successive benzannulations red-shift both the absorption and the emission bands, and reduce the first oxidation potential.

A two-step chemical wet etching processes were used to investigated the formation and the plane indexes of exposed etched facets of wet etching patterned sapphire substrate (PSS). It was found when SiO 2 mask still remained on the top c-plane, the structure of PSS comprised of a hexagonal pyramid covered with six facets {3 417} with a flat top c-plane. When SiO 2 mask were etched away, beside six facets on the bottom, there were 3 extra facets {1 105} exposed on the top.

We report simple ideas for grain control by using active cooling and crucible insulation for high‐quality multi‐crystalline silicon (mc‐Si) growth for solar cells. The method employed an active cooling spot to induce initial dendrite growth, and the solidification front was controlled to be slightly convex through crucible insulation. It was found that the percentage of grains having twins was significantly increased by the present approach. The dislocation density for those grains was also significantly lower. More importantly, the successful improvement showed that the grain size and the minority carrier lifetime increased along the growth direction. And the laser beam induced current (LBIC) measurement also showed much higher quantum efficiency for the twin area. Copyright © 2010 John Wiley & Sons, Ltd.

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Plant oils have been used as environmentally benign lubricants since they present high viscosity index and flash points and low evaporation loss. Triacylglycerols (TAG) are the major components of naturally occurring oils and fats and are able to produce high strength lubricant films. One of the main concerns that hinders the usage of triacylglycerols as lubricants, however, is the thermal stability of these molecules. In this paper, we report on the effect of chain structure on density, viscosity, and thermal stability of triacylglycerols using molecular dynamics simulations. The selected triacylglycerols are trilauroylglycerol (LLL-TAG), tristearoylglycerol (SSS-TAG), trans-trioleoylglycerol (trans-OOO-TAG), and trans-trilinolenoylglycerol (trans-LeLeLe-TAG). The first two TAGs are saturated molecules with a different number of carbons in the chain, and the second two TAGs are monounsaturated and polyunsaturated molecules, respectively. The computed results demonstrate that the length of the aliphatic chain influences the physical properties of triacylglycerols. TAGs with short chain (LLL-TAG) show higher density than TAGs with longer chains. Viscosity is determined by the degree of recoil of the aliphatic chains and by the number and location of unsaturated bonds. Thermal stability, as represented by the ability of triacylglycerols to stay in a disordered phase during the cooling process, is related to the order-disorder phase transition temperature. Since the phase transition temperature can be correlated to the thermal stability during the cooling process, LeLeLe-TAG shows the highest thermal stability among the systems considered. These results can aid in the design of molecules with specific lubrication properties.

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