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An ability to lift off or separate the thin-film polycrystalline CdTe from the CdS, without the use of chemical etches, has enabled direct electrical characterization of the asprocessed CdTe near the CdTe/CdS heterointerface. We use this ability to understand how a back-contact, nitric-phosphoric (NP) etch affects the grain boundaries throughout the film. Quantitative determination of the grain-boundary barrier potentials and estimates of doping density near the grain perimeter are determined from theoretical fits to measurements of the current vs. temperature. Estimates of the bulk doping are determined from high-frequency resistivity measurements. Also, a variable doping density within the grains of non-etched material has been determined. These results allow a semi-quantitative grain-boundary band diagram to be drawn that should aid in determining more-accurate two-dimensional models for polycrystalline CdTe solar cells.

A low-cost, non-contact sensor that provides endpoint detection for each stage in a three-stage CuIn x Ga 1Àx Se 2 (CIGS) deposition is described. CIGS and precursor emissivity data providing the fundamental basis for the sensor's operation are presented. In situ operation of the sensor is outlined and sensor-predicted film thickness, maximum Cu ratio during growth, as well as final Cu ratio are compared with those derived by other methods. Characteristics of the sensor relevant to automated and continuous processing are discussed.

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