Application of the Terrestrial Photovoltaic Module Accelerated Test-to-Failure Protocol

The Terrestrial Photovoltaic Module Accelerated Test-to-Failure Protocol was applied to seven crystalline silicon module types to test the durability of the various module constructions on a quantitative basis in chamber and to evaluate the protocol itself. The modules under test are subdivided into three accelerated lifetime testing paths: 85°C/85% relative humidity with system voltage bias, thermal cycling between - 40°C and 85°C, and paths that alternate between humidity with bias (one in each polarity) and thermal cycling. Three of the module types were also fielded to ascertain degradation mechanisms occurring in the natural environment for comparison to the mechanisms seen in the accelerated testing. Potential induced-degradation in modules negatively biased and silicon nitride antireflective coating thinning on cells in modules positively biased are among the important mechanisms that are seen both in the modules stressed in the natural environment and in chamber. Junction box failure, cell breakage, and acid-assisted metallization degradation are included in the mechanisms seen in chamber tests, and they vary significantly between module types. Per a goal of the accelerated test protocol, we found examples of modules with components and process methods that showed degradation mechanisms that occurred faster than incumbents that had satisfactory field experience. These were evaluated as opportunities for durability improvement. Conversely, types that showed substantial improvement were also seen, especially with respect to system voltage stress durability.