Experimental setup for camera-based measurements of electrically and optically stimulated luminescence of silicon solar cells and wafers

We report in detail on the luminescence imaging setup developed within the last years in our laboratory. In this setup, the luminescence emission of silicon solar cells or silicon wafers is analyzed quantitatively. Charge carriers are excited electrically (electroluminescence) using a power supply for carrier injection or optically (photoluminescence) using a laser as illumination source. The luminescence emission arising from the radiative recombination of the stimulated charge carriers is measured spatially resolved using a camera. We give details of the various components including cameras, optical filters for electro- and photo-luminescence, the semiconductor laser and the four-quadrant power supply. We compare a silicon charged-coupled device (CCD) camera with a back-illuminated silicon CCD camera comprising an electron multiplier gain and a complementary metal oxide semiconductor indium gallium arsenide camera. For the detection of the luminescence emission of silicon we analyze the dominant noise sources along with the signal-to-noise ratio of all three cameras at different operation conditions. © 2011 American Institute of Physics

Luminescence emission from forward- and reverse-biased multicrystalline silicon solar cells

We study the emission of light from industrial multicrystalline silicon solar cells under forward and reverse biases. Camera-based luminescence imaging techniques and dark lock-in thermography are used to gain information about the spatial distribution and the energy dissipation at pre-breakdown sites frequently found in multicrystalline silicon solar cells. The pre-breakdown occurs at specific sites and is associated with an increase in temperature and the emission of visible light under reverse bias. Moreover, additional light emission is found in some regions in the subband-gap range between 1400 and 1700 nm under forward bias. Investigations of multicrystalline silicon solar cells with different interstitial oxygen concentrations and with an electron microscopic analysis suggest that the local light emission in these areas is directly related to clusters of oxygen. © 2009 American Institute of Physics

Developments in silicone technology for use in stoma care

YesSoft silicone's flexibility, adhesive capacity and non-toxic, non-odourous and hypoallergenic nature have made it an established material for adhesive and protective therapeutic devices. In wound care, silicone is a component of contact layer dressings for superficial wounds and silicone gel sheeting for reducing the risk of scarring, as well as of barriers for incontinence-associated dermatitis. Regarding stoma accessories, silicone is established in barrier films to prevent contact dermatitis, adhesive removers to prevent skin stripping and filler gels to prevent appliance leaks. Until recently, silicone has not been used in stoma appliances flanges, as its hydrophobic nature has not allowed for moisture management to permit trans-epidermal water loss and prevent maceration. Traditional hydrocolloid appliances manage moisture by absorbing water, but this can lead to saturation and moisture-associated skin damage (MASD), as well as increased adhesion and resultant skin tears on removal, known as medical adhesive-related skin injury (MARSI). However, novel silicone compounds have been developed with a distinct evaporation-based mechanism of moisture management. This uses colloidal separation to allow the passage of water vapour at a rate equivalent to normal trans-epidermal water loss. It has been shown to minimise MASD, increase wear time and permit atraumatic removal without the use of adhesive solvents. Trio Healthcare has introduced this technology with a range of silicone-based flange extenders and is working with the University of Bradford Centre for Skin Sciences on prototype silicone-based stoma appliance flanges designed to significantly reduce the incidence of peristomal skin complications, such as MARSI and MASD. It is hoped that this will also increase appliance wear time, reduce costs and improve patient quality of life

Effects of heterogeneous surface boundary conditions on parameterized oceanic deep convection

Vertical mixing and deep convection are routinely parameterized inbasin-scale and global ocean general circulation models. Theseparameterizations are designed to work with homogeneous surfaceboundary conditions for an individual grid cell. A partial icecover, however, yields heterogeneous fluxes of buoyancy that arenot resolved by the computational grid. In idealized scenarios,the effects of such heterogeneous surface boundary conditions areexplored by comparing coarse resolution models with three commonparameterizations for mixing and deep convection with large eddysimulations (LES) of free convection. Generally, models withparameterized convection reproduce the temperature profiles of theLES reference accurately when the surface boundary conditions areresolved by the grid. Significant biases are introduced when thesurface boundary conditions are not resolved and buoyancy fluxesare averaged horizontally. These biases imply that mixing depthsmay locally be too shallow in large scale simulations withoutproper handling of heterogeneous boundary conditions duringconvective events; also the grid-cell averaged density may bevertically homogenized within the shallow boundary layer.Adaptation of present mixing schemes may overcome these spuriouseffects of horizontally averaging the surface buoyancy fluxes

Experimental study and velocity scaling of the tip-leakage noise generated by low-speed axial flow-fans

The present paper reports of an experimental study of the broad band and the tip leakage noise generated by axial flow fans employed for automotive cooling systems. Two operating points and three different configurations, with and without tip leakage flow, have been considered. The measurements have been taken in a hemi-anechoic chamber at constant rotational speed and during speed ramps, and the problem of the scaling of the different noise components has been faced. The acoustic response function of the test configuration, computed by means of the spectral decomposition method, has been compared with the SPL at constant Strouhal number. The comparison has shown that the acoustic response strongly affects the trend of the SPL spectra and results in a complicated dependence on the rotational speed. However, the analysis of the acoustic propagation function demonstrates that the broad band noise and the tip leakage noise scale with different power laws but are both affected by the same propagation effect. The scaling law also depends on the operating point