6 March 2014 Silver-free solar cell interconnection by laser spot welding of thin aluminum layers: analysis of process limits for ns- and μs-lasers
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Abstract
We investigate a laser welding process for contacting aluminum metallized crystalline silicon solar cells to a 10-μm-thick aluminum layers on a glass substrate. The reduction of the solar cell metallization thickness is analyzed with respect to laser induced damage using SiNx passivated silicon wafers. Additionally, we measure the mechanical stress of the laser welds by perpendicular tear-off as well as the electrical contact resistance. We apply two types of laser processes; one uses one to eight 20-ns-laser pulses at 355 nm with fluences between 12 and 40 J/cm2 and the other single 1.2-μs-laser pulses at 1064 nm with 33 to 73 J/cm2. Ns laser pulses can contact down to 1-μm-thick aluminum layers on silicon without inducing laser damage to the silicon and lead to sufficient strong mechanical contact. In case of μs laser pulses the limiting thickness is 2 μm.
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H. Schulte-Huxel, H. Schulte-Huxel, S. Blankemeyer, S. Blankemeyer, S. Kajari-Schröder, S. Kajari-Schröder, R. Brendel, R. Brendel, } "Silver-free solar cell interconnection by laser spot welding of thin aluminum layers: analysis of process limits for ns- and μs-lasers", Proc. SPIE 8967, Laser Applications in Microelectronic and Optoelectronic Manufacturing (LAMOM) XIX, 896716 (6 March 2014); doi: 10.1117/12.2037628; https://doi.org/10.1117/12.2037628
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