Wire and wire-mesh plating
Silicon cells deliver clean current to copper conductors which in turn bundle it and deliver it to the consumers from the module via copper cable.
The solders of the copper conductors used in the module must have a low smelting temperature in order not to damage the silicon cells. For a long time, this was possible only with tin/lead (Sn/Pb) 60/40 or very similar highly leaded alloys. For the new generation of modules, unleaded low-melting solders are in use or being tested by now. Indium/tin (InSn), tin/bismuth (Sn/Bi), or tin/bismuth/silver (SnBiAg) are examples.