Investigating Reliability Attributes of Silicon Photovoltaic Cells: An Overview
Reliability attributes are being developed on a wide variety of advanced single-crystal silicon solar cells. Two separate investigations: cell-contact integrity (metal-to-silicon adherence), and cracked cells identified with fracture-strength-reducing flaws are discussed. In the cell-contact-integrity investigation, analysis of contact pull-strength data shows that cell types made with different metalization technologies, i.e., vacuum, plated, screen-printed and soldered, have appreciably different reliability attributes. In the second investigation, fracture strength was measured using Czochralskli wafers and cells taken at various stages of processing and differences were noted. Fracture strength, which is believed to be governed by flaws introduced during wafer sawing, was observed to improve (increase) after chemical polishing and other process steps that tend to remove surface and edge flaws.
Contact integrity testing of stress-tested silicon terrestrial solar cells
A test procedure was developed and applied to terrestrial silicon solar cells in order to determine the effect of accelerated environmental and time-temperature aging on metal contact integrity. Quantities of cells of four different manufacturers were given the contact integrity test after being subjected to accelerated stress tests that included forward bias-temperature, thermal cycle and thermal shock, power cycle, and bias-temperature humidity tests at two temperature-humidity levels. Significant effects due to certain stress tests were found for some cell types. It is concluded that cells fabricated using plated nickel/solder metallization showed significantly more serious contact integrity degradation than silver-metallized cells.
Amphotericin B microspheres: A therapeutic approach to minimize toxicity while maintaining antifungal efficacy
Amphotericin B microsphere formulations with and without addition of polyethylene glycol 2000 in cross-linked bovine serum albumin were prepared. Amphotericin B microspheres were characterized for particle size (<5 µm), zeta potential (∼30 mV) and drug interaction by DSC and FTIR and were found to be stable formulations. Drug release profiles for these microspheres revealed that the release was primarily by diffusion. In vitro toxicity as assessed by release of haemoglobin and potassium demonstrated no toxic effect as compared with conventional solution formulation. Antifungal activity in vitro was comparable to solution formulation when tested by broth dilution method.