Minority-carrier diffusion lengths on both sides of the CuxS/CdS heterojunction in polycrystalline thin-film solar cells were determined from the decay of the short-circuit current generated by a 20-keV electron beam traversing the junction. The measured diffusion lengths in the low-field regions of these cells ranged from 0.11 to 0.57 μm for electrons in the p-type cuprous sulfide and from 0.07 to 0.31 μm for holes in the n-type cadmium sulfide. Uncertainties introduced by surface recombination effects, internal fields, and experimental accuracy specified that the actual bulk diffusion lengths could range from 0.09 to 1.71 μm for minority electrons in the cuprous sulfide and from 0.06 to 0.44 μm for minority holes in the cadmium sulfide. Measurement and analysis errors were estimated to cause bulk diffusion lengths to differ from measured values by less than the worst case limits of +200 and −31%.
Technical performance measures (TPMs) are tools that show how well a system is satisfying its requirements or meeting its goals. This paper presents the BAE National Security Solutions TPM process and a TPM template. It gives lessons learned from piloting it on a program.
The atmosphere within a furnace chamber is a basic factor in achieving the desired chemical reactions with metals during heat treating. This article presents the fundamentals of heat treating atmospheres, and describes two groups of atmosphere control, namely, furnace atmosphere control and supply atmosphere control. The two basic types of atmospheric supply systems are generated atmospheres and nitrogen-base atmospheres. The article provides a brief overview of the gas reactions associated with oxidation and carbon control to ensure either carburization, or to prevent decarburization. It demonstrates how the carbon potential control is achieved by controlling water vapor concentration, carbon dioxide concentration, or oxygen partial pressure. The article also describes the various devices and analyzers used to monitor sampled gas from furnace atmospheres, namely, chromatographs, oxygen probes, Orsat analyzers, infrared analyzers, dewpoint analyzers, and hot-wire analyzers. Finally, it discusses the advantages, disadvantages, and limitations of these analyzers.
Heat treaters regularly seek ways to prevent and reduce rework and scrap loads by implementing procedures and tools to make sure the heat treating process meets customer expectations and specifications. One process parameter requirement is to ensure consistent atmosphere carbon content. Measuring carbon absorption into steel is commonly done to verify atmosphere consistency. This article describes an atmosphere carbon potential analyzer that provides a cost-effective way to measure carbon using a wire coil that functions in a way similar to using shim stock.
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