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This work presents a detailed analysis of a new two-layer process to contact industrial solar cells. However, most of the results seem to be transferable to standard screen print paste contacts. The seed layer was created by a pad or screen printer and thickened by light-induced plating (LIP) of silver. These contact structures were investigated microscopically to gain a better understanding of the observed electrical parameters. A review of the present microscopic contact formation model for flat surfaces is presented. This model was extended and applied to surfaces textured with random pyramids. This analysis has revealed two new types of silver crystallites which can be described by a crystallographic model. The dependence of the silver crystallite density on the surface doping concentration was investigated. Next, the dependence of the contact resistance on the width of the seed layer was measured showing that the contact resistivity increases with a reduction of the seed layer width. These results have been further approved by an analysis of SEM images of wet-chemically etched contacts examining the density of crystallites and the fraction of removed SiNx layer. Contact resistance R-C measurements before and after LIP of silver showed surprisingly a positive influence of tire plating process on R-C. A detailed microscopical analysis revealed four new possible current flow paths due to the LIP of a conventional contact or a seed layer. The results led to an extension of the existing model for a screen printed contact

This work presents the results of a detailed series resistance characterization of silicon solar cells with screen-printed front contacts using hotmelt silver paste. Applying the hotmelt technology energy conversion efficiencies up to 18.0% on monocrystalline wafers with a size of 12.5 cut X 12.5 cut have been achieved, an increase of 0.3% absolute compared to cells with conventional screen-printed contacts. This is mainly due to the reduction in the finger resistance to values as low as 14 Omega/m, which reduces the series resistance of the solar cell significantly. To retrieve the lumped series resistance as accurately as possible under the operating condition, different determination methods have been analyzed. Methods under consideration were fitting of the two-diode equation function to a dark IV-curve, integration of the area A under an IV-curve, comparison of a j(sc)-V-oc with a one-sun IV-curve, comparison of the jsc and V-oc points of a shaded curve with the one-sun IV-curve as well as comparison of a dark IV-curve with a one-sun IV-curve, and comparison of IV-curves measured at different light intensities. The performed investigations have shown that the latter four methods all resulted in reliable series resistance values

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Fraunhofer ISE's concept for an advanced metallization of silicon solar cells is based on a two-step process: the deposition of a seed layer to form a mechanical and electrical contact and the subsequent thickening of this seed layer by a plating step, preferably by light-induced plating (LIP). The concept of a multi-layer metallization is used for most of the relevant high-efficiency cell types in industry. The main advantage of this concept is that each layer can be optimized individually, i.e. the seed layer to achieve an optimal electrical and mechanical contact and the plated layer in terms of high lateral conductivity and good solderability. Solar cells results with seed layers fabricated by aerosol printing, chemical Ni plating on cells with a laser-structured dielectric layer and laser-enhanced Ni plating are presented