Researchers from Germany’s Fraunhofer ISE and US panel manufacturer Solaria have applied thermal laser separation and post-metallation passivated edge technology to the production of tunnel oxide passivated contact cells (TOPCon). They have developed shingle PV devices that are more efficient than cells built using conventional laser writing and mechanical cutting methods.
“To the best of our knowledge, this is the first publication dealing with TOPCon tile solar cells separated by thermal laser separation (TLS) and edge passivated using passivated edge technology (PET),” said researcher Elmar Lohmüller. pv magazine. “PET is a patented development by Fraunhofer ISE that can be used to correct the shear losses of today’s half-cut, third-cut or shingle solar cells through simple, efficient post-processing of individual cells.”
Fraunhofer ISE already filed a patent application in 2018 and offers samples to partners interested in the technology. Solaria is one of the first industrial partners to test post-metallization PET in TOPCon shingle solar cells.
“The PET approach could address a key need in the industry – to mitigate the efficiency losses from cutting cells and to do so in a cost-effective manner,” Solaria spokesman Ricky Dunbar said. pv magazine. “Our collaboration with Fraunhofer ISE has shown that PET can effectively reduce these losses in TOPCon tile cells with promising efficiency.”
The proposed fabrication process uses thermal laser separation (TLS) instead of conventional laser writing and mechanical cutting (LSMC) to isolate the cells. TLS requires only a short initial laser scribe with a cutting laser and a water-air aerosol jet to create an initial crack that can then propagate through the wafer in any direction.
“This leads to cuts with very smooth edge surfaces,” the researchers explained, noting that TLS was performed via a microDICE laser system developed by Germany’s 3D-Micromac.
“The TLS process optimized in this work produces up to 0.2% more efficient tile cells immediately after differentiation compared to tile cells isolated from LSMC,” the researchers said, noting that the TLS-based cell achieved a power conversion efficiency of 22.0% “It has been shown that TLS can performed in such a way that the passivation quality of the surface does not deteriorate in the vicinity of the dividing line.”
The research team presented their findings in “TOPCon shingle solar cells: Thermal laser separation and passivated edge technology,” which was recently published Advances in solar power.
“Since we are still in the development phase of an industrial PET tool, valid data on the yield ratios of both approaches for reliable cost calculation are not yet available,” said Lohmüller. “However, PET will add a process step that, to our current knowledge, is easily scalable to current capacity requirements, so the demonstrated efficiency gains have significant potential to more than offset the additional costs.”