Screen Printed Fire-Through Contact Formation for Polysilicon-Passivated Contacts and Phosphorus-Diffused Contacts

Abstract

In this article, we investigate the passivation quality and electrical contact properties for samples with a 150 nm thick n+ polysilicon layer in comparison to samples with a phosphorus diffused layer. High level of passivation is achieved for the samples with n+ polysilicon layer and an interfacial oxide underneath it. The contact properties with screen-printed fire-through silver paste are excellent (no additional recombination from metallization and specific contact resistivity (ρc) ≤ 2 mΩ·cm2) for the samples with the polysilicon layers. Fast-firing peak temperature was varied during the contact formation process; this was done to see the trend in the contact properties with the change in the thermal budget. The differences in the J0met and ρc for the two different kinds of samples are explained with the help of high-resolution scanning electron microscope imaging. Finally, we prepare M2-sized n-passivated emitter rear totally (PERT) diffused solar cells with a 150 nm thick n+ polysilicon based passivated rear contact. The best cell achieved an efficiency of 21.64%, with a Voc of 686 mV and fill factor of 80.2%.