Abstract
High-efficiency silicon solar cells have potential applications on mobile electronic and electrical vehicles. The fabrication processes for high-efficiency cells necessitate complicated processes and expensive materials. Ti/Pd/Ag metal contacts have only been used in limited areas in spite of their good stability and low contact resistance because of expensive materials and processes. Commercial solar cells with screen-printed contacts formed by using Ag paste suffer from a low fill factor and a high shading loss because of high contact resistance and low aspect ratio. Low-cost Ni and Cu metal contacts have been formed by using electroless plating and electroplating techniques to replace the Ti/Pd/Ag and screen-printed Ag contacts. Nickel-silicide formation at the interface between the silicon and the nickel enhances stability and reduces the contact resistance, resulting in an energy conversion efficiency of 20.2 % on a 0.5 ${\Omega}cm$ FZ(Float Zone) wafer. A tapered contact structure has been applied to large-area, $6.7\;{\times}\;6.7\;cm^2$, solar cells in order to reduce power loss due to the front metal contact. The tapered metal contact is realized by electroplating and results in $45\;cm^2$ solar cells with efficiencies of 21.4 % on 2 ${\Omega}cm$ FZ wafer.