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PIN solar cells were light soaked up to 60 hours. The cell characteristics, the optoelectronic properties and the microstructure parameter (R = I2100/I2100+I2000) as well as the hydrogen content (CH) and density of states (g(Ef)) of the active i-layer were monitored throughout the entire light induced degradation process and compared with the correspondents μτ product (for both carriers) inferred through steady photoconductivity and FST measurements. Data show a strong correlation between the decrease of μτ product for electron and the increase of the fraction of hydrogen bonded on internal surfaces (R increases from 0.1 to 0.4) suggesting structural changes during the light induced defects' formation. For holes, the μτ product remains approximately constant and only dependent on the initial hydrogen content. As g(Ef) increases, μτ presents an asymmetrical decrease showing that electrons are more sensitive to defects' growth than holes. We also observe that the rate of degradation is faster for samples having the lowest defect densities, R and CH, showing that the amount of degradation is not a simple function of the photon exposure (Gt product) but also depends on the material microstructure.

This paper deals with a new model and structure able to tailor defects in pin devices. The model assumes the usual density of states profile, including donor and acceptor like states inside the mobility gap and has the capability to simulate the transient and steady state device behavior. The new structure is based in two interfacial defectous layers, located at the junctions, acting as "gettering" centers to tailor the defects. The role of the interlayer and its thickness on device performances will be also discussed. © 1993.

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A study using a primary Cs’ beam to carry out positive SIMS on conductive samples is presented. The energy distribution of positive secondary ions was measured and the sputter yield, S’ was calculated for several elements, The significantly different energetic behavior found between the secondary cesium ions and those ejected from the target will be discussed. Finally, the best conditions to perform positive SIMS with such a primary beam will be described.

Mode of operation and area of rnhanced efficiency for series-resonant converters is presented. Frequency control on voltage source DC-DC converters is discussed and other principles of control are introduced. Optimum modes of operation for power transistor resonant converters are also considered. For even better efficiency a resonant current shaping is discussed.

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