Copper–Nickel Alloy Plating to Improve the Contact Resistivity of Metal Grid on Silicon Heterojunction Solar Cells

Abstract: As a dominant metallization technique of crystalline silicon solar cells, screen printing with silver paste has been generally used in photovoltaic industries. In case of the silicon heterojunction solar cells (SHJ) structure, a metal contact with silver paste has lower electrical conductivity than pure silver due to the other compositions of the paste. For the reason, copper plating is attractive substitute for the silver paste since the plated-copper contacts have high conductivity and easily reduce line width which is beneficial to light absorption. In this experiment, we studied copper–nickel (Cu–Ni) alloy plating to form a seed layer of the copper plating on an indium tin oxide (ITO) layer which is used for the transparent conductive oxide of the SHJ solar cells. As a requirement of suitable seed layer, contact resistivity (ρ_c) between the seed and the ITO is important to obtain high fill factor by decreasing series resistance of solar cells. Contact resistivity values of the samples with varied nickel contents in the Cu–Ni films were extracted by using transfer length method. Also, the composition ratio of the alloy layer was analyzed by energy dispersive spectrometer. Moreover, X-ray diffraction was used to compare lattice parameter and crystallite size of the film. Graphical Abstract: [Figure not available: see fulltext.].