Grid Line Spacing Research Articles

Understanding and Control of Compressively Buckled Semiconductor Thin Films

We report the controllable buckling of free-standing thin-film semiconductor metamaterials using a thin-walled structure spanning $\mathrm{Au}$ grid supports. The buckling is developed by compressing the $\mathrm{Au}$ grids, increasing the internal air pressure during the bonding of $\mathrm{Au}$ pads on the semiconductor to the grids, resulting in upward deformation. The stiffness of the free-standing semiconductor beam is controlled by the grid line spacing, as verified for a wide range of out-of-plane deformations, ranging from nearly flat to microns for grid line spacings from 20 to 150 \textmu{}m, respectively. We also observe telephone-cord and domelike buckling as the grid line spacings and layer thicknesses are varied. Finite element analysis quantitatively predicts the shape and magnitude of the film deflection. We propose strategies to apply the distorted free-standing metamaterials for thermal energy harvesting, optical reflectors, and pressure sensors.

High-Performance Transparent Copper Grid Electrodes Fabricated by Microcontact Lithography for Organic Photovoltaics

We report high-performance transparent copper grid electrodes on glass and plastic substrates that offer a higher Haacke figure-of-merit than conventional indium tin oxide electrodes and are well-matched to the requirements for organic photovoltaics (OPVs). The electrode is fabricated using microcontact lithography with a combination of molecular resist and low toxicity etchant, namely, hexadecanethiol and aqueous ammonium persulfate. This approach to electrode fabrication is much faster than conventional lithography because it takes 20 times narrower than is possible using conventional metal printing methods and so a grid pitch <30 μm is easily achieved without increasing metal coverage. The very small grid-line spacing relaxes the requirement to use highly conductive films to span the gaps between grid lines, reducing parasitic absorption losses. This is demonstrated using an extremely thin (10 nm) poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) layer. Additionally, we present evidence that it is not always necessarily to embed the metal grid into the substrate or to planarize with a charge-transport layer, to avoid leakage current across the OPV device.

Highly transparent and excellent electromagnetic interference shielding hybrid films composed of sliver-grid/(silver nanowires and reduced graphene oxide)

Transparent electromagnetic interference (EMI) shielding materials are highly in demand for liquid crystal display, communication devices and observation windows. In this study, two polyethylene terephthalate (PET) substrates, one printed with a silver-grid and the other coated with silver nanowires and reduced graphene oxide (AgNWs/rGO), were prepared separately and hot-pressed together face-to-face to fabricate hybrid films composed of sliver-grid/(AgNWs/rGO). The rGO nanosheets act as bridges between silver nanowires and vice-versa which can facilitate fast transfer of electrons. The effects of grid-line spacing on the transparency and EMI shielding have been studied. It is found that the EMI shielding increases with decreasing the grid-lines spacing, however, resulting in decrease of the transparency. The silver-grid/(silver nanowires and reduced graphene oxide) sample with 1.0 mm grid-line spacing demonstrates highest EMI shielding of 42.94 dB along with a low sheet resistance of 1.60 Ω/sq and a high transparency of 74.40%.

Correcting distortion errors in memory of object locations: the example of grid line spacing in topographic maps

ABSTRACTThe omnipresence of orientation, wayfinding and navigation tasks in everyday life calls for high-quality cartographic media that help people to solve their tasks in the best possible way. Modern maps should not only consider modern visualization techniques and design approaches but also knowledge on the map user’s cognitive processing. Previous studies of cognitive cartography and spatial cognition identified grids as suitable cartographic elements that can enhance the accuracy of cognitive representations of geographic space. Grid lines form grid cells and these cells subdivide a map layout into different regions. These regions seem to contribute to a categorization of cartographically represented contents. The categorical organization of a map provides a superordinate spatial structure that can improve the recall of object locations. An important parameter influencing categorization is the distance between grid lines (spacing/separation). A previous study suggested 5 cm (paper distance) spacing as being suitable for an accurate performance in recalling object locations in topographic maps. Based on a recall-memory-paradigm adopted from experimental studies in cognitive psychology, the experiments reported in the present study take up this value and aim at specifying the ideal value of grid line spacing for object location memory. The results show that previous findings can be extended. The results allow the proposal of ideal grid line spacing in a 6.5-7.5 cm range. These spacing values help to reduce spatial distortion errors in the memory of object locations, especially in maps with a low amount of visual details.

The Effects of Grid Line Separation in Topographic Maps for Object Location Memory

Research from the field of cognitive psychology provides evidence that cognitive representations of space based on maps or map-like sketches are subject to systematic distortion tendencies. These distortions influence the orientation capacity as they represent errors in spatial memory. Map grids are a traditional feature of map graphics that has rarely been considered in research on spatial distortions in cognitive maps. Grids traditionally assist the map reader in finding coordinates and objects, but they also provide a systematic and homogeneous structure for dividing up map information into smaller units supporting perception and spatial memory. In a previous study it was shown that grids improve object location memory. The aim of this study was to determine whether different sizes of grid cells have an effect on the quality of object location memory. Therefore, an empirical study including the test performances of 33 participants was carried out: the memory performance was measured as both the percentage of correctly recalled object locations (hit rate) and the mean distance errors of correctly recalled objects (spatial accuracy). Three different intervals of grid line spacing (Separation) were applied to topographic maps. These maps varied in their type of characteristic geographical areas, accompanied by three different levels of map complexity (Landscape). The results of this study show that both factors have an impact on object location memory in topographic maps.

Hybrid metal grid-polymer-carbon nanotube electrodes for high luminance organic light emitting diodes

Organic light emitting diodes (OLEDs) incorporating grid transparent conducting electrodes (TCEs) with wide grid line spacing suffer from an inability to transfer charge carriers across the gaps in the grids to promote light emission in these areas. High luminance OLEDs fabricated using a hybrid TCE composed of poly(3,4-ethylenedioxythiophene) poly(styrenesulfonate) (PEDOT:PSS PH1000) or regioregular poly(3-hexylthiophene)-wrapped semiconducting single-walled carbon nanotubes (rrP3HT-SWCNT) in combination with a nanometre thin gold grid are reported here. OLEDs fabricated using the hybrid gold grid/PH1000 TCE have a luminance of 18 000 cd m−2 at 9 V; the same as the reference indium tin oxide (ITO) OLED. The gold grid/rrP3HT-SWCNT OLEDs have a lower luminance of 8260 cd m−2 at 9 V, which is likely due to a rougher rrP3HT-SWCNT surface. These results demonstrate that the hybrid gold grid/PH1000 TCE is a promising replacement for ITO in future plastic electronics applications including OLEDs and organic photovoltaics. For applications where surface roughness is not critical, e.g. electrochromic devices or discharge of static electricity, the gold grid/rrP3HT-SWCNT hybrid TCE can be employed.

Silver Contact Grid: Inferred Contact Resistivity and Cost Minimization in 19% Silicon Solar Cells

The analysis of silicon solar cell contacts having an H-bar front grid pattern is extended by enabling the contact resistivity to be inferred from the measurement of total series resistance and the determination of six individual components of series resistance. Analysis of the contact system was completed for a representative 19% cell fabricated from a 156-mm pseudosquare p-Cz wafer using standard production processes, including phosphorus ion implantation, thermal oxide surface passivation, silicon nitride deposition, and screen-printing and firing of front silver gridlines and busbars, back silver soldering pads, and back aluminum contact. Gridline width was measured to be 80 μm after firing, with an average thickness of 7.4 μm and an effective resistivity of 4.7 μΩ·cm. Contact resistivity to the uniform 91 Ω/ <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$\square$</tex></formula> emitter was inferred to be 5.3 mΩ·cm <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$^{2}$</tex></formula> from the total series resistance and its components. Using these values, gridline spacing was optimized for maximum efficiency (1.7 mm, 91 lines, 19.1%, $0.040/W) or minimum silver cost (2.1 mm, 74 lines, 19.0%, $0.038/W). The analysis methodology was further applied to examine the impact of gridline width and silver pricing on cell efficiency and incremental cost. Such analysis can serve as a guideline for future contact system designs when the cost of silver changes or when printing technology allows narrower lines.

Finite difference on grids with nearly uniform cell area and line spacing for the wave equation on complex domains

A finite difference time-dependent numerical method for the wave equation, supported by recently derived novel elliptic grids, is analyzed. The method is successfully applied to single and multiple two-dimensional acoustic scattering problems including soft and hard obstacles with complexly shaped boundaries. The new grids have nearly uniform cell area ( J -grids) and nearly uniform grid line spacing ( α γ -grids). Numerical experiments reveal the positive impact of these two grid properties on the scattered field convergence to its harmonic steady state. The restriction imposed by stability conditions on the time step size is relaxed due to the near uniformity cell areas and grid line spacing. As a consequence, moderately large time steps can be used for relatively fine spatial grids resulting in greater accuracy at a lower computational cost. Also, numerical solutions for wave problems inside annular regions of complex shapes are obtained. The use of the new grids results in late time stability in contrast with other classical finite difference time-dependent methods.

Generation of curvilinear coordinates on multiply connected regions with boundary singularities

A new algorithm to generate smooth two-dimensional boundary conforming coordinates, with grid lines control, on multiply connected regions including boundary singularities, is devised. The technique fits into the category of elliptic grid generators, since it is based on the numerical solution of Poisson equations. The physical domain D is transformed into a topologically equivalent connected rectangular domain D ′ by defining a branch cut inside D . Control of the grid line spacing over the multiply connected regions is established by appropriately distributing nodal points on the branch cut, and on other boundary curves. Simple and computationally convenient expressions for the control functions, present in the Poisson system, are obtained from this initial distribution of points. Thus, a natural link between clustering properties and the control functions is created. Fixing the nodal points on the branch cut causes the convergence of the numerical method about the singular boundary points. An iterative smoothing process relocating the branch cut is described. As a result, smooth grids are obtained. Grid quality analysis shows that coordinate line orthogonality in the new meshes is superior than in similar grids obtained from a well-known commercial software. The algorithm is successfully tested over a variety of multiply connected domains. The computational advantage of this novel grids is revealed by using them to numerically model the vibrations of complexly shaped annular membranes.

Rapid measurement of the spatial resolution of colour flow scanners

An acoustic grid for rapid measurement of the spatial resolution of colour velocity images is described. The grid is composed of alternate widths of acoustic window and acoustic attenuator. Attenuation is provided by the use of a layer of waterproof paper, which is wrapped in close contact with a tube of a flow phantom. The colour image consists of several closely spaced lines. When the grid line spacing is less than the spatial resolution, the colour lines cannot be separately visualised. The use of several grids of different spacing provides a measure of the spatial resolution. It is shown that the spatial resolution is dependent on the position of the focal zone.

Silicon solar cell with a novel low-resistance emitter structure

A silicon solar cell with over 19% efficiency at 100 suns, AM1.5, 20 °C, incorporating a novel front contact geometry, has been demonstrated. The cell has one third of its frontal area covered with metal and grid line spacing of 82 μ, as measured along the silicon surface. It uses V-groove etching, angle-contact metal evaporation, and a cover glass to allow high fractional grid coverage with low obscuration, thereby minimizing emitter resistance losses at high concentrations.

Numerical and Experimental Investigation of the Oscillating Wake of a Blunt-Based Body

The oscillating wake of a blunt-based body is examined using explicit finite-difference solutions of the Vorticity Transport equation and Poisson's equation. The difference equations are formulated for a rectangular grid with varying grid line spacing. Utilization of this type of grid allows increased accuracy to be obtained in the regions of highest gradients, without the large increases in computation time associated with refining a uniformly spaced grid. The accuracy of the numerical solutions was verified, qualitatively, by a comparison with an experimentally obtained flow pattern, and quantitatively, by a comparison with experimentally obtained Strouhal numbers. The basic parameters governing the problem were found to be the thickness and profile of the boundary layers on the body prior to separation, and the Reynolds number. The Reynolds number based on the base height was varied in the range from 100.0 to 16,295.0, while the boundary-layer thickness was varied in the range from 0.121 to 3.0 base heights. The numerical solutions in this area exhibited three types of wake oscillations. The first type of oscillation involved the alternate growth and decay of circulation regions, which remained attached to the base of the body. In the second type of oscillation, the circulation regions would grow in size and eventually detach from alternating sides of the base. The third type of wake oscillation appears to be a more violent version of the second type, again involving growth and detachment of circulation regions from the base of the body. The flow pattern in the third type of oscillating wake closely resembles that of the classic von Karman vortex street.

Optimization of Contact Grid Spacing for High Solar Flux Photovoltaic Cells

A method for obtaining the optimum gridline spacing for photovoltaic cells operating at high solar fluxes is presented. Using a distributed resistance and diode model of a photovoltaic cell, a differential equation is obtained which relates voltage to position on the cell surface. This equation was solved numerically to obtain the maximum power point efficiency. The maximum power point efficiency is shown to depend upon five dimensionless groups which are combinations of basic cell parameters, geometric parameters, and the solar flux level. The results are presented in graphical form from which the optimum gridline spacing can be obtained for any desired incident solar flux. In addition, the variation in the performance of any specified cell can be obtained from the graphs as a function of the solar flux level.