Contact resistivity and adhesion of copper alloy seed layer for copper-plated silicon heterojunction solar cells

Abstract

To reduce optical loss and contact material cost in silicon heterojunction (SHJ) solar cells, copper plating has been considered as a suitable metallization technique. However, a plated copper contact on indium tin oxide (ITO) generally has low adhesion reliability. For this reason, suitable seed layer materials are required for adhesive copper plating. As a requirement of a suitable seed layer material, contact resistance between the seed and the ITO is also important, as well as the adhesion, since a high series resistance results in a low fill factor. In this work, we applied copper alloy (Cu-X) materials as a seed layer that was deposited by co-evaporating copper with other metals. The contact resistivity (ρ c ) values of the Cu-X seed layer and copper-plated contact with the Cu-X seed layer (Cu-X/Cu) on the ITO layer were evaluated by the transfer length method (TLM). Also, tape tests were carried out to check the adhesion of the Cu-X/Cu contact.

Direct Electroplating on Indium-Tin-Oxide-Coated Textured and Polished Silicon Substrates via Transition Metal Alloyed Interlayers

“…Initially evaporated Cu seed layers with subsequent electroplating were also shown to have good adhesion. [4][5][6] However, the metal evaporation technique needs a high vacuum chamber and does not provide high-throughput.…”