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In partnership with the NREL/DOE PV Manufacturing R&D Program, Energy Conversion Devices, Inc. (ECD) has developed a comprehensive set of online diagnostic systems that allow real-time measurement of PV device characteristics in-situ during amorphous silicon (a-Si) deposition, prior to deposition of ITO, PV device characteristics measured include open-circuit voltage (Voc), charging rate (CR), and thickness (t) of each of the three cells in the triple-junction device. Measurements are made with an rms precision of about 0.05%, and at periods of 1 s to 1 min (1 cm to 1 m). The information from these systems is displayed real-time in the control room for online quality assurance (QA) and trouble-shooting. The diagnostics systems have been incorporated into software feedback loops to control film thicknesses. We are now beginning the development of programs for continuous online optimization.