Investigation of SHJ Module Degradation: A Post- Mortem Approach

We present a “post-mortem” procedure for analyzing degradation of fielded photovoltaic modules. We use this procedure to investigate degradation mechanisms in silicon heterojunction (SHJ) modules. We study cell fragments cored from two modules, one operated in the field for a decade and one stored in the dark as a control. We find that both the front surface passivation and bulk have likely been degraded. Through comparisons of spectral photoluminescence emissions, we conclude that although an increase in density of the pre-existing types of radiative defects is possible, it seems that any new defects types are purely non-radiative.