Influence of Silicon Substrate Surface Finish on the Screen-Printed Silver Metallization of Polysilicon-Based Passivating Contacts

Abstract

Passivated contact based on a thin interfacial oxide and a highly doped poly-silicon layer has emerged as the next evolutionary step to increase the efficienciesof industrial silicon solar cells. To take maximum advantage from this layer stack,it is vital to limit the losses at the metal polysilicon interface, which can bequantified as metal polysilicon recombination current density (J0met) and contactresistivity. In cell concepts, wherein a large variety of silicon substrate surfacefinish can be obtained, it is essential to know how the surfacefinish affects the J0met and contact resistivity. Herein, commercially availablefire through silverpaste and the metal-polysilicon recombination current densities and contactresistivity are used for three different silicon substrate surfacefinishes, namely:planar or saw damage etched (SDE), chemically polished in acidic solution andalkaline pyramidal textured. Contact resistivity values below 3 mΩcm2withJ0met in order of the recombination current density of the doped region (J0pass) areobtained for samples with planar surface for both 150 and 200 nm nþpolysiliconlayer thicknesses. The results presented in this work show that the samples withflat substrate morphology outperform the samples with textured surfaces.