Nomenclature and Description of EL Observations: Cell Cracks and Other Findings

Crystalline silicon solar cells were, are and will dominate the Photovoltaic module market. In the past decade a lot of work was done to better understand and characterize findings utilizing Electroluminescence EL to look into the appearance of c-Si solar cells. Even standards work was done, however, a clear definition based on a standard is still missing. Within the project PV-Riss, a group, including manufacturers, advisory experts and research facilities, is working on an overview of different findings in the literature (typically of Al-BSF and PERC cells) and bringing this into the context of today’s cell technologies (TOPCon, HJT, IBC…), multi-Busbar (more then 6), large(r) cells (M6, M10(R), M12(R)) and larger module sizes with even varying constructions (glass/backsheet vs glass/glass). The first step is to agree on a clear wording and description of certain findings. These will be presented in this contribution and a few examples are given in the “experimental results”. Besides the clear nomenclature of certain findings, the location within the module is relevant for clear and comprehensive communication. Therefore, a chessboard pattern is proposed on how to clearly locate cells within the different module types, including half-cut, third-cut, and even shingled module layouts. The final result from the project will be published as the English VDE-SPEC 90031 that is targeted to be published in Q4 2024. Depending on the results and feedback the VDE-SPEC can also serve as an IEC NWIP, e.g. within the IEC 62446-series or as a significant update to IEC 60904-13. A detailed paper is submitted to EPJ Photovoltaics.