Structural analysis of thin film silicon PV modules by means of large area laser beam induced current measurements

The spatial variation of key properties of large area silicon thin film PV modules is investigated using a Laser Beam Induced Current (LBIC) system. The system produces a very detailed current mapping of devices, allowing the identification of spatially varying structural defects of photovoltaic modules. It allows for efficient defect detection as well as investigations of localised performance variation. In this paper, the results are shown for large area single junction amorphous silicon modules from different manufacturers that have been installed outdoors for more than two years. Several defects are identified as probable sources of poor performance and low efficiency of some devices. Some of the major contributions to these defects are likely to occur during the production process while some are developed during outdoor exposure.