Three-Terminal Bipolar Junction Bottom Cell as Simple as PERC: Towards Lean Tandem Cell Processing
Michael Rienäcker1,2, Emily L. Warren3, Tobias F. Wietler1,2, Adele C. Tamboli3, Robby Peibst1,2
1Institute for Solar Energy Research in Hamelin (ISFH), Emmertal, Germany
/2Institute for Electronic Materials and Devices at Leibniz Universität Hannover, Hanover, Germany
/3National Renewable Energy Laboratory, Denver, CO, United States

Silicon-based tandem cells can upgrade the dominating PERC technology and greatly increase the conversion efficiency. A novel approach, the three-terminal (3T) tandem using interdigitated back-contact (IBC) cells, was shown to combine the advantages of four- and two-terminal tandem cells at the expense of a more complex bottom cell fabrication process. In this paper, we propose a simplified and lean PERC-like 3T bipolar junction bottom cell featuring two minority carrier selective contacts and a single majority carrier selective contact, and thus resembling a bipolar junction transistor architecture. We present the lean PERC-like fabrication process and explain the working principle by using current-voltage measurements of illuminated 3T IBC cells.