Quantification of Front Side Metallization Area on Silicon Wafer Solar Cells for Background Plating Detection

This work describes a method to measure the metallized area on the front side of silicon wafer solar cells. The method is especially applicable to detect and quantify background plating, which can occur in the production of solar cells with plated front-side metallization. The metallized area of plated solar cells is determined by an image processing algorithm (“MetDetect”) using images of the solar cell front side obtained by a simple commercially available flatbed scanner. The algorithm is verified by the comparison of scanned images from test samples with microscope images. Furthermore a correlation of the metallized area with the measured short-circuit current density of the samples justifies the proposed method. With “MetDetect” a precise quantification of the background plating on the plated solar cell front side can be realized. It is suitable for inline inspection in solar cell production or quantification of pinholes and cracks in the surface dielectric. In this work “MetDetect” is applied to corroborate the observation that background plating of solar cells with a nickel copper front side metallization can surprisingly be removed during plating by a thin Sn-capping.