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Both-sides-contacted solar cells are the preferred choice for industrial production due to their lower complexity.

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Ninety percent of the photovoltaic (PV) systems in use worldwide are made from silicon cells. The theoretical efficiency limit of such cells is 29.4 percent, but until now, the only systems that have approached it have been special IBC solar cells, with both metal contacts at the rear. All of that has changed since The Fraunhofer Institute for Solar Energy Systems (ISE) published a record conversion efficiency of 26 percent for both-sides-contacted (BSC) silicon cells in a Nature Energy article this month.

BSC cells are the preferred choice for industrial production due to their lower complexity. The novel “TOPCoRE” cell uses TOPCon (Tunnel Oxide Passivating Contact) technology, first developed at the ISE, which combines the advantages of very low surface recombination losses with efficient charge carrier transport – on both sides. In effect, this allows for higher voltages and “fill factors” than in cells that have a collecting emitter on the front.

Detailed power loss analysis shows that the novel cell compensates for and minimizes both electron and hole transport losses and recombination losses. "Based on a systematic simulation-based analysis, we were able to derive some fundamental design rules for future high-efficiency silicon solar cells above 26 percent efficiency. Both-sides-contacted solar cells have the potential to reach efficiencies up to 27 percent and thus surpass the previous world record for silicon solar cells," explains Professor Stefan Glunz, division director of Photovoltaics Research at the ISE in a press release.

Moreover, the innovative cell structures can be mass-produced using existing technologies: the cells connect up to form a module in the same way as industry standard solar cells.