Use of the Suns-Voc for diagnosing outdoor arrays & modules

The Suns-Voc technique has been widely used in both industrial settings and in research and development laboratories to characterize the fundamental behavior of photovoltaic diodes. Its application spans the development of metallization pastes, to novel thin-film technologies, to the failure analysis of high-efficiency c-Si modules. One area in which the technique has been used in only a limited fashion is in the analysis of modules and arrays in the field. This paper examines the application of the technique to outdoor measurements and highlights an under-utilized analysis method available to data sets from the field that include Voc as a function of illumination. Specifically, by comparing the module or array I-V curve with the Suns-Voc curve, the mismatch losses, shunting losses, and series resistance losses can be quantified. By tracking these parameters over time, module and array degradation can be monitored and broken down by mechanism.