More interesting insights unveiled by Electroluminescence testing. It’s a fairly common defect to find backsheet scratches on modules in the field. Upon close visual inspection, often they are nothing more than a slight indentation mark on the rear of the modules. However, in more severe cases, such as what we’ve found following the resent spate of storm damage, you do see scratches which actually penetrate the multi-layered laminations of the module and impact on the cell structure.
Often backsheet scratches are wrongly diagnosed as microcracks during an EL analysis. The main characteristic to look out for is that microcracks are contained to the cell they are affecting. Microcracks don’t jump over the gap between the cells and start on another cell. So when you see a continuous line reaching across multiple cells, 9 time out of 10, it’s a backsheet scratch.
The other interesting observation we’ve seen is sometimes on the front of the modules you’ll see ‘snail-trails’ in one continuous line reaching across multiple cells. This is a visual indication of a backsheet scratch. Check the back of the module and it will be there.
What we are seeing under EL with these extreme storm related backsheet scratches is that there is so much force applied, that they have indeed caused microfractures in the respective cells. Not only that, many modules with these extreme scratches will be condemned as the electrical insulation of the module is compromised.
Let us know if you suspect backsheet scratches on your modules. We can carry out a visual inspection and determine whether they are affecting the output of the modules.