Comparison of diode quality plus other factors in polycrystalline cells and modules from outdoor and indoor measurements

The Outdoor Test Facility (OTF) at NREL is equipped with data acquisition systems that monitor the performance of modules deployed outdoors in real time, including the measurement of current-voltage traces every 15 minutes during all daylight hours. This affords us the ability to analyze performance across many levels of illumination which allows the determination of factors that affect module performance and that serve as indicators of module quality, including average diode quality factors, series resistances values, and reverse-saturation currents of the cells. This study focuses on several polycrystalline thin-film modules, including cadmium telluride. CIS, and polycrystalline silicon. We present these parameters, acquired from outdoor measurements, and compare the results with measurements obtained from more canonical methods.