Fraunhofer ISE said it had developed a low-cost rear contact Tunnel Oxide Passivated Contact ‘TOPCon’ n-Type solar cell that has achieved a conversion efficiency of 24%.
According to Fraunhofer ISE TOPCon provides a passivated contact across the entire rear surface of the cell, while achieving improved surface passivation, reducing resistance losses.
“We developed a selective passivated contact that allows the majority carriers to pass and prevents the minority carriers from recombining,” noted Dr. Martin Hermle, Head of Department “High-Efficiency Silicon Solar Cells” at Fraunhofer ISE. “TOPCon consists of an ultrathin tunnel-oxide and a thin silicon layer. The surface passivation is of excellent quality and the rear contact poses little resistance for the charge carrier transport.”
The research centre noted that a key hurdle in reaching high efficiencies with n-Type wafer/cells is the patterning scheme of the rear contact as the rear side metal contacts are an efficiency limiting factor.
The TOPCon cell was said to provide a simple rear contact without any patterning required, reducing costs and process complexity as only a small fraction of the rear area is contacted.
“We have now developed a simple rear contact without any patterning, with which we have achieved an excellent efficiency of 24 percent for an n-type solar cell,” said Dr. Stefan Glunz, Division Director, Solar Cells – Development and Characterization at Fraunhofer ISE.