On the metastability of silicon heterojunction solar photovoltaic modules

Silicon heterojunction (SHJ) solar modules gained strong interest from solar photovoltaic (PV) module manufacturers and in the global market due to their high-efficiency potential. However, the presence of an amorphous silicon layer in SHJ structures raises concerns about their stability under light exposure. In this article, we compare the stability of SHJ modules to the stability of p-type and n-type homojunction monocrystalline silicon modules and of several thin-film PV technologies. The analysis is performed in intermediate precision conditions of measurement, where the same modules are measured indoors with the same measurement procedure, same location and equipment, and over an extended period of time, during which the modules are kept stored and not exposed to light. The results from all tested SHJ modules, which were also confirmed in reproducibility conditions, show a slow exponential degradation in the dark, which is fully recovered when the module is subsequently light-soaked. With this behavior, SHJ modules recall the metastability of certain thin-film technologies.