Energy yield considerations based on the BO-related defect

The boron-oxygen-related defect is formed under illumination and passivated under illumination at higher temperatures in silicon wafers. A model is set up combining the kinetics of the BO-related defect with the carrier injection density in PERC solar cells, its power behavior and an energy yield calculation of a PV system. The carrier injection dependent regeneration rate is discussed and reported values of the effective attempt frequency are parameterized carrier injection dependent. The model and its parameter are validated at published degradation and regeneration data from relevant industry companies with a good match. Thus, the model is used to calculate the temporal defect populations development over ten years for a climate data set of Halle (Central Europe). It is found that the recombination active defect complex is formed to over 95% after 100 days mainly from January to March during the first year, the defect passivation is reached to about 30% within the first year occurring in summer months and to over 90% in the 7^th year. The calculation of the energy yield loss for 20 years PV system lifetime is below 0.4%_rel compared to the light-induced degradation unaffected case. Thus, the PV system energy yield loss of 0.4%_rel during system lifetime is much lower compared to 2.15%_rel maximal power degradation of the modeled PERC solar cell. BO-related defect regeneration during solar cell processing might be therefore to be reconsidered under economic and quality considerations. A sensitivity analysis on the regeneration rate does not change this picture much.