A Detailed Analysis Of Visible Defects Formed In Commercial Silicon Thin-Film Modules During Outdoor Exposure

We analyzed defects in silicon thin-film tandem (a-Si: H/mu c-Si: H) modules from an outdoor installation in India. The inspection of several affected modules reveals that most of the defects - which optically appear as bright spots - were formed primarily nearby the separation and series connection laser lines. Cross-sectional SEM analysis reveals that the bright spots emerge due to electrical isolation, caused by a delamination of the cell from the front TCO in the affected area. In addition, the morphology of the a-Si: H top cell differs in the delaminated area compared to the surrounding unaffected area. We propose that these effects are potentially caused by an explosive and thermally triggered liberation of hydrogen from the a-Si: H layer. Electrical and thermal measurements reveal that these defects can impact the cell performance significantly.