Printed Dopant Sources for Locally-Doped SiOx/Poly-Si Passivating Contacts

This paper presents an industrially relevant solution for the formation of local passivating contacts for back-contact back-junction (BC-BJ) solar cells, based on inkjet- and screen-printing of dopant inks and pastes. The successful realization of passivating contacts utilizing printing technologies is a crucial prerequisite to simplify the fabrication process of BC-BJ cells while approaching theoretical efficiency limit of silicon solar cells. In this work, dopant inks and pastes as well as the printing parameters are tuned in order to establish a high passivation quality within c-Si/SiOx/poly-Si lifetime samples. The impact of the anneal/diffusion conditions on the surface passivation are studied. Excellent passivation quality is achieved for inkjet-printed n-type (phosphorus) poly-Si surfaces with implied open-circuit voltage iVOC of 726 mV and implied fill factor iFF of 86.2%. On p-type, iVOC of 692 mV and iFF of 82.8% and iVOC of 700 mV and iFF of 82.4% where measured by utilizing inkjet and screen-printing, respectively. Similar results were realized by Ion-implanted surfaces, herein used as the reference, underlining the high potential of the investigated printing processes.