Gold-silicon nanofiber synthesized by femtosecond laser radiation for enhanced light absorptance

In this study, we devised a new concept for the precise nanofabrication of Au-Si fibrous nanostructures using megahertz femtosecond laser irradiation in air and atmospheric pressure conditions. The weblike fibrous nanostructures of Au thin layer on silicon substrate, which are proposed for the application of solar cells, exhibit a specific improvement of the optical properties in visible wavelength. Varying numbers of laser interaction pulses were used to control the synthesis of the nanofibrous structures. Electron microscopy analysis revealed that the nanostructures are formed due to the aggregation of polycrystalline nanoparticles of the respective constituent materials with diameters varying between 30 and 90 nm. Measurement of the reflectance through a spectroradiometer showed that the coupling of incident electromagnetic irradiation was greatly improved over the broadband wavelength range. Lower reflectance intensity was obtained with a higher number of laser pulses due to the bulk of gold nanoparticles being agglomerated by the mechanism of fusion. This forms interweaving fibrous nanostructures which reveal a certain degree of assembly.

Gold-silicon nanofiber synthesized by femtosecond laser radiation for enhanced light absorptance

In this study, we devised a new concept for the precise nanofabrication of Au-Si fibrous nanostructures using megahertz femtosecond laser irradiation in air and atmospheric pressure conditions. The weblike fibrous nanostructures of Au thin layer on silicon substrate, which are proposed for the application of solar cells, exhibit a specific improvement of the optical properties in visible wavelength. Varying numbers of laser interaction pulses were used to control the synthesis of the nanofibrous structures. Electron microscopy analysis revealed that the nanostructures are formed due to the aggregation of polycrystalline nanoparticles of the respective constituent materials with diameters varying between 30 and 90 nm. Measurement of the reflectance through a spectroradiometer showed that the coupling of incident electromagnetic irradiation was greatly improved over the broadband wavelength range. Lower reflectance intensity was obtained with a higher number of laser pulses due to the bulk of gold nanoparticles being agglomerated by the mechanism of fusion. This forms interweaving fibrous nanostructures which reveal a certain degree of assembly.

Effective CdS/ZnO nanorod arrays as antireflection coatings for light trapping in c-Si solar cells

The cell with CdS/ZnO nanorod array (NRAs) antireflection coatings exhibits lower reflectance and better light trapping ability than the c-Si solar cell.

The color of night: Surface color perception under dim illuminations

Several studies document rudimentary color vision under dim illumination. Here, hue perceptions of paper color samples were determined for a wide range of light levels, including very low light levels where rods alone mediate vision. The appearances of 24 paper color samples from the OSA Uniform Color Scales were gauged under successively dimmer illuminations from 10–0.0003 Lux. Triads of samples were chosen representing each of eight basic color categories; red, pink, orange, yellow, green, blue, purple, and gray. Samples within each triad varied in lightness. Observers sorted samples into groups that they could categorize with specific color names. Above 0.32 Lux, observers sorted the samples into the originally chosen color groups with few exceptions. For 0.1–0.01 Lux, the red and orange samples were usually correctly identified as either red or orange. The remaining samples tended to be grouped into two categories, associated with the scotopic sample reflectance. The lowest reflectance samples were below threshold and were named black. The higher reflectance group was named predominately as green or blue-green (three observers; the fourth observer used blue or achromatic). At the three dimmest levels (≤ 0.0032 Lux) there continued to be conspicuous color percepts. Color categories were reliably assigned based on relative sample scotopic lightness. Of the samples above threshold, those with lower reflectance were classified as red or orange (all observers) and the higher reflectance samples as green or blue-green (three observers) or achromatic or blue (the fourth observer). Rods and L-cones presumably mediated color percepts at the intermediate light levels used in the study. At the three lowest light levels there were distinct color appearances mediated exclusively by rods. We speculate that at these light levels the visual system estimates probable colors based on prior natural experience.

Perylene Diimide as the Black-Layer Material of the OLEDs

ABSTRACTIn this paper, we use a perylene diimide derivative serving as a destructive and an absorption layer of the “black cathode” of an organic light-emitting device (OLED). A thin and semitransparent metal between the electron transport layer and the perylene diimide is used for better electron injection and also serves as the destructive interference. The thickness of such layer is critical since thinner metal results in lower reflectance, but higher diving voltage due to worse electron injection. To enhance the electron injection capability, the thickness of the thin metal increases which in turns to increase the reflectance. Here, we used a double-metal configuration to decrease the reflectance and maintain the electron injection capability at the same time.

Application of Light Microscopy to Direct Coal Liquefaction Research

Light microscopy was used to analyze the effects of added catalyst at different conditions (temperature and reaction times) in liquefaction testing of a low pyritic sulfur bituminous coal. Quantitative changes in vitrinite/vitroplast reflectance of coal and liquefaction residues were shown to be useful markers in analyzing and understanding the role of catalyst during the initial stage of coal particle hydrogenation. Lower reflectance values corresponded to increased conversions up to about the 60 min and 375°C experimental conditions. Microscopical observation of liquefaction residues also revealed the presence of “wall scales” of varying width.

Variation in Infrared Reflectance of Eucalyptus Radiata Dc.

Various workers have reported that green plants which are diseased or in need of water have a lower infrared reflectance and consequently a blue image on false colour film. The infrared reflectance of E. radiata leaves rises as they become dry, and produces no blueness of the false colour image. It is suggested that blue images of E. radiata recorded in the field are due to lower reflectance of the infrared wavelengths by flowers. Water stress is not likely to be detected on false colour film until the plants are visibly affected.