High and Low Work Function Materials for Passivated Contacts

The tunnel oxide passivated contact (TOPCon) is a promising technology improving the efficiency of Si solar cells by cutting recombination losses and simplifying the solar cell design (1D junction design). The objective of this paper is to investigate possible contact materials having a high/low work function for passivated contacts thereby enabling the realization of a double-sided contact Si solar cell featuring n-type TOPCon on the front and p-type TOPCon at the rear side. The main part of this paper deals with the eligibility of thin atomic layer deposited (ALD) AZO (aluminum doped zinc oxide) interlayers sandwiched between n-TOPCon and ITO (tin doped indium oxide) in order to avoid sputter damage. It will be demonstrated that the insertion of ALD AZO improved the efficiency by 0.8% abs. and lead to a maximum efficiency of 20.2%. Finally, WOx and MoOx which have a high work function are identified as promising contact layers for p-TOPCon.