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The present study applied Sn−0.7Cu−0.2Zn alloy solders to a photovoltaic ribbon. Intermetallic compounds of Cu₆Sn₅ and Ag₃Sn formed at the Cu/solder/Ag interfaces of the module after reflow. Electron probe microanalyzer images showed that a Cu−Zn solid-solution layer (Zn accumulation layer) existed at the Cu/solder interface. After a 72 h current stress, no detectable amounts of Cu₆Sn₅ were found. However, a small increase in Ag₃Sn was found. Compared with a Sn−0.7Cu photovoltaic module, the increase of the intermetallic compounds thickness in the Sn−0.7Cu−0.2Zn photovoltaic module was much smaller. A retard in the growth of the intermetallic compounds caused the series resistance of the module to slightly increase by 9%. A Zn accumulation layer formed at the module interfaces by adding trace Zn to the Sn−0.7Cu solder, retarding the growth of the intermetallic compounds and thus enhancing the lifetime of the photovoltaic module.