Advances with Resist-Free Copper Plating Approaches for the Metallization of Silicon Heterojunction Solar Cells
The metallization of silicon heterojunction (SHJ) solar cells by selective Cu electroplating without any resist-mask is in development. A thin multi-functional PVD Cu-Al stack is deposited to mask the ITO and to promote homogeneous current distribution for simultaneous bifacial plating. This investigation reviews different approaches to perform the Al-patterning - by printing of a metallic ink, laser metal transfer or selective metal etching - to produce a metal-seed susceptible to plate selectively against the self-passivated Al surface. This NOBLE - native oxide barrier layer for selective electroplated, metallization allows reaching a first promising efficiency of 20.0% on a full area SHJ solar cell with low contact resistivity to ITO. This simultaneous bifacial metallization features several advantages: low temperature processing, high metal conductivity of plated copper, no organic masking and low material costs (almost Ag free).