Scanning Acoustic Microscopy as a Non-Destructive Method for the Investigation of PV Module Components

The application of new non-destructive testing for the inspection of photovoltaic modules is needed to advance the assessment of module quality and, thereby, improve their long-term performance. Scanning Acoustic Microscopy (SAM) has proved to be a powerful technique for the investigation of failures and defects in a great range of materials, including solar cells and modules. In this work, defects in PV modules are analyzed by SAM and the images are compared with well-established non-destructive methods, such as Dark Lock-In Thermography (DLIT) and Electroluminescence (EL). Acoustic micrographs were collected from different layers of the module and allowed the visualization and assessment of depth profiles of the embedded PV module components individually. SAM can detect irregularities on the encapsulant, backsheet and the solar cell at high lateral resolution and help elucidate defects detected with the other techniques. Moreover, the acoustic beam can be focused at the encapsulant/cell interface to visualize eventual failures occurring on these two layers separately. Therefore, SAM delivers complementary information to EL and DLIT on the quality of PV modules

Analysis of Shingle Interconnections in Solar Modules by Scanning Acoustic Microscopy

Scanning Acoustic Microscopy (SAM) is applied as a non-destructive testing to image the electrically conductive adhesive (ECA) joints used to connect shingled solar cells. The advantage of SAM is the possibility of imaging the internal structure of the material, which enables the visualization of the depth profile. In this work, we demonstrate the suitability of SAM for detecting ECA failures in shingled cells that are embedded within a solar module. Shingled interconnected cells were prepared by intentionally applying ECA strips equally spaced apart between adjacent cells. Single acoustic images from different layers inside shingle modules were obtained, as well as acoustic cross-sections. X-ray imaging was carried out to compare with the images obtained by SAM. Additionally, Electroluminescence imaging was further carried out to compare the electrical performance of the shingled cells with the physical distribution of the ECA joints. The results reveal that SAM is capable of imaging the structure of the ECA inside solar modules, and distinguishing intact ECA from defective adhesive areas. Therefore, SAM can be applied as a complementary technique to the qualitative analysis of ECA joints