Exploratory Surface Assessment of POE-Rich Residues on Field-Aged Crystalline Silicon Cell Fragments After Femtosecond NIR Post-Treatment

This exploratory study examined whether visible native cell texture alone verified chemical cleanliness in selected fields on fragments from one field-aged crystalline-silicon photovoltaic module with polyolefin elastomer (POE)-rich encapsulant. After preparatory laminate opening, eight single-pass femtosecond near-infrared (fs-NIR) raster programs were applied. Optical profilometry described 77 local regions within 24 fields. Scanning electron microscopy and energy-dispersive X-ray spectroscopy (SEM/EDS) examined corresponding local fields, spatially separate from the profilometry measurements. A visibly textured pre-fs-NIR reference field yielded 9.23 wt.% C in the original normalized EDS output. Selected treated fields showed irregular morphology and regional carbon signals. Visible texture therefore did not verify chemical cleanliness in the examined fields. Overall, the screening did not establish a reproducible, chemically verified cleaning outcome. Spatially unmatched observations and purposive sampling prevent the quantification of residue removal or ranking of the programs; EDS does not uniquely identify carbon as POE. Further work requires measurements at the same locations before and after irradiation, independent specimens, and a predefined chemical cleaning criterion.