Selective Copper Electroplating on Patterned Self-Assembled Monolayers for Photovoltaic Applications

The photovoltaic industry is expected to consume 30–50% of the global silver supply by 2030, indicating the need for using other materials for solar cell metallization processes. We report herein a low-cost and scalable mask of phosphonic acid (PA) self-assembled monolayers (SAMs) on indium tin oxide (ITO) for nickel and copper electroplating on solar cells. Octadecylphosphonic acid and 12-azidododecylphosphonic acid were deposited using different procedures and characterized by cyclic voltammetry and etching resistance tests to assess the barrier properties of the SAMs. It was found that the PA chemical functionalization and the deposition method strongly affect the masking properties of SAMs. The underlying PA binding modes were investigated using attenuated total reflectance Fourier transform infrared spectroscopy, which revealed that the heterocondensation reaction between 12-azidododecylphosphonic acid and ITO was promoted during heating. Patterning of SAMs was performed using UV-C radiations to achieve selective electroplating of nickel and copper on ITO.