Electrical properties of fine line printed and light-induced plated contacts on silicon solar cells

The properties of fine-line printed contacts on silicon solar cells, in combination with light-induced plating (LIP), arc presented. The seed layers are printed using an aerosol system and a new metallization ink called SISC developed at Fraunhofer ISE. The influence of multiple layer printing on the contact geometry is studied as well as the influence of the contact height on the line resistivity and on the contact resistance. The dependence between contact resistance and contact height is measured using the transfer length model (TLM). Further on, it is explained by taking SEM images of the metal semiconductor interface, that a contact height of less than 1 mu m or a minimum ink amount of only 4-6 mg is sufficient to contact a large area (15.6 cm x 15.6 cm) silicon solar cell on the front side and results in a contact resistance R-c x W < 0.5 Omega cm. As the line resistivity of fine-line printed fingers needs to be reduced by LIP, three different plating solutions are tested on solar cells. The observed differences in line resistivity between rho(f) = 5 x 10(-8) and 2 x 10(-8) Omega m are explained by taking SEM pictures of the grown LIP-silver. Finally, the optimum LIP height for different line resistivities is calculated and experimentally confirmed by processing solar cells with an increasing amount of LIP silver. Copyright (C) 2010 John Wiley & Sons, Ltd.