Scientists from Germany’s Fraunhofer Center for Silicon Photovoltaics CSP have developed a new process aimed at lowering the series resistance of monocrystalline PERC solar cells.
The new technique was tested in partnership with German company CE Cell Engineering GmbH. “Contacting surface structures (emitters) of solar cells with high sheet resistance is already technically possible, but costly,” said Stephan Großer, project manager in the diagnostics and metrology group at Fraunhofer CSP. “The series resistance of the contact structure on the solar cell increases due to high contact resistances, which significantly reduces the efficiency of a solar cell. In the project, we were able to lower the series resistance by using laser-assisted current treatment and elucidate the active principle.”
Through this process, which was dubbed laser enhanced contact optimization (LECO), the researchers were able to identify faulty semiconductor-to-metal contacts in the PERC cells and to establish where there was insufficient electrical contact formation between the metal and semiconductor. Furthermore, all this happened without damaging the solar cells. “The optimization of the contact takes place through a large number of microscopic current-fired contact points, which enable … very low series-resistance between the metallic silver contact finger and the doped silicon wafer,” the research team further explained.
The Fraunhofer CSP is currently evaluating the LECO process parameters for patenting.
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