Inkjet-Printing of Phosphorus and Boron Dopant Sources for Tunnel Oxide Passivating Contacts

This paper presents inkjet-printing of phosphorus and boron dopant inks for the formation of tunnel oxide passivating contacts (TOPCon) for back-contact back-junction (BC-BJ) silicon solar cells. The successful realization of passivating contacts utilizing printing technologies is a crucial prerequisite to simplify the fabrication process of BC-BJ cells while approaching the theoretical efficiency limit of silicon solar cells. In this work, the focus is set on developing inkjet printing processes for the application of dopant sources towards higher precision, homogeneity of printed lines and lifetime, in order to establish high passivation quality for TOPCon. Excellent passivation quality is achieved for inkjet-printed n-type (phosphorus) poly-Si surfaces with an implied open-circuit voltage iVOC of up to 733 mV and an implied fill factor iFF of up to 86.4%. For p-type (boron) poly-Si, iVOC of up to 682 mV and iFF of 80.6% were achieved. Similar results were realized by ion-implanted poly-Si surfaces, herein used as the reference, underlining the high potential of the investigated printing processes.