The importance of surface roughness in the adhesion of electroless-plated metal in inkjet printed grooves

Good metal to silicon adhesion is essential in achieving high fill factor and low series resistance in high-efficiency solar cells, and electroless plating has provided a cost-effective method of metallising the grooves of these cells. Unfortunately the smoothness and shallowness of grooves created using inkjet printing can limit the mechanical adhesion of the deposited metal. In this paper we examine the importance of roughness in achieving a successful adhesion between electroless-deposited nickel and the silicon surface in inkjet printed grooves. We investigate several low HF or HF-free chemical solutions commonly used for etching the surface of inkjet-printed grooves with minimum impact on the sensitive dielectric layer. We conclude by presenting a roughening technique suitable for inkjet printed solar cell fabrication.