Zincate processes for silicon solar cell metallization

To allow plating on aluminum, zincate processes are introduced in metallization of silicon solar cells. Different zincate solutions are investigated regarding their adhesion on typical solar cell surface morphologies. Sufficient adhesion (>1.5 N/plus 45 degree rule}mm) on PVD aluminum layers is demonstrated by zincate processes with subsequent plating of nickel, copper and silver on both random pyramid and damage etched surfaces. Small-size (4 cm2) back-contact back-junction solar cells with an aluminum or aluminum-silicon seed layer are successfully processed in this way. On screen printed aluminum, adhesion has been found to be below 1 N/plus 45 degree rule}mm. Microstructural investigation of the failure mode reveals that the aluminum peels off the silicon surface in this case.