Laser Assisted Separation Processes for Bifacial pSPEER Shingle Solar Cells
In this paper, two laser-assisted separation processes (i) laser scribe and mechanical cleaving (LSMC) and (ii) thermal laser separation (TLS) for the separation of p-type silicon shingled passivated edge, emitter and rear (pSPEER) solar cells are examined. Both separation processes involve two process steps, where one of them is considered the main laser process that is conducted along the whole separation path (laser scribe for LSMC and laser cleave for TLS). We analyze the influence of the main laser process as well as the complete separation process of both, LSMC and TLS, on the electrical performance of pSPEER solar cells. We include an investigation of the dependency on the separation side, i.e. emitter (front side) or emitter-free side (rear side). It is found that by conducting the LSMC process from the front side, a significantly lower energy conversion efficiency by = -1.9%abs in comparison to the rear side process is observed which originates in particular from a lower pseudo fill factor pFF = -7.5%abs. This is attributed to local ablation of the p-n-junction leading to increased j02-like recombination. By conducting the laser scribe without subsequent mechanical cleaving of host cells, we measure pFF = -9.1%abs in comparison to the initial host cell measurement. This indicates that the laser ablation process itself leads to the strong pFF and losses observed after LSMC separation of pSPEER cells. In comparison, the TLS process is found to be invariant to the processed cell side. It is shown that in this case, the involved laser cleave process itself has no measurable impact on the performance of unseparated host cells.