Analysis of PV modules based on thin film solar cells by dark measurements technique

The dark measurements technique which were developed to analyze the material properties of solar cells in a PV module and performed either at DC or at AC conditions, can give useful information on the quality of the active material. This technique leads to better understanding the PV module degradation processes, occurring during indoor qualification testing or in real operating conditions. To this purpose an indoor testing laboratory has been set up to detect and monitor the PV modules degradation. A simple technique, based on the analysis of the behaviour of PV devices biased by an AC signal on dark conditions, has been developed to easily and quickly evaluate some parameters like the series, the shunt resistances and the capacitance affecting their electrical characteristics. In the present paper the technique basic concepts will be illustrated. Preliminary experimental results, achieved by applying the technique to some kinds of PV modules based on simple and triple junction's silicon amorphous solar cells, will be presented.