Bill of Materials Variation and Module Degradation in Utility-Scale PV Systems

PV modules of the same make and model are often assembled with different bills of materials (BOMs). We describe two case studies of utility-scale silicon PV systems in which these differing BOMs were associated with faster-than-expected degradation. In one of the sites we found that different metallization paste had been used for grid lines in some cells leading to loss of contact to the cell and severe series resistance degradation. In another site, we found that two different types of cell had been used, one of which suffered from light and elevated temperature induced degradation (LeTID). Our results from both sites underscore that variations in BOM, even among modules of the same make and model can lead to reliability challenges.