Innovative Methods for Low-Temperature Contact Formation for Photovoltaics Applications

Interest in silicon heterojunction with intrinsic thin layer and newly proposed wider bandgap carrier selective contact solar cells in recent years motivates the investigation of low temperature contact formation in order to preserve the order of electronic quality of these layers as well as the chemical surface passivation provided by hydrogenated passivation layers. The realization of low temperature contacts may also broaden solar cell and other optoelectronic devices opportunities, e.g. to use thermally sensitive materials, such as flexible polymer substrates, while at the same time reducing the thermal budget expended on device fabrication. In this work, two methods for low-temperature ohmic contact formation are investigated. The first is a rapid localized annealing technique using electromagnetic induction and the second a deposition method using inkjet printing of reactive silver inks. These techniques are evaluated for use in solar cell devices (not only silicon-based) by comparing demonstrated properties to those targeted for front contacts to solar cells, i.e. finger width, aspect ratio, resistivity, specific contact resistance, and apparent adhesion.