25.7% Tandem Solar Cell Efficiency Reported

• A team of Canadian and Saudi researchers have reported 25.7% efficiency for perovskite-silicon tandem solar cells
• They increased the thickness of the perovskite layer to effectively cover all peaks and valleys of the silicon wafer
• For their research, the team also enhanced charge separation by coating perovskite crystals in a passivation later made of 1-butanethiol
• Tandem cells were seen to have reduced their performance only slightly when these were exposed to temperatures of up to 85° Celsius for more than 400 hours

Germany's Fraunhofer Institute for Solar Energy (ISE) has certified a 25.7% perovskite and silicon tandem solar cell that was created by researchers from the University of Toronto Engineering and King Abdullah University of Science and Technology (KAUST).

The team achieved this efficiency level by overcoming what they say is a 'key obstacle' for tandem solar cells. Their approach meant increasing the thickness of the perovskite layer to cover the peaks and valleys created by tiny pyramidical structures. They also enhanced charge separation by coating the perovskite crystals in a 'passivation layer' made of a common industrial chemical, 1-butanethiol.

Little loss of performance was seen for these tandem solar cells during the research, as these were able to withstand temperatures of up to 85° Celsius for more than 400 hours. Researchers from both the teams are now working on improving their design to enable stability increase for up to 1,000 hours.

"The fact that we can do all this without modifying the silicon makes it a drop-in solution," said ECE postdoctoral fellow and lead author of the paper that's been published in the journal Science, Yi Hou. "Industry can apply this without having to make costly changes to their existing processes."

The research paper published in Science journal is titled Efficient tandem solar cells with solution-processed perovskite on textured crystalline silicon.

In January 2020, Germany's HZB researchers reported 29.15% conversion efficiency for perovskite and silicon tandem solar cells which was also confirmed by Fraunhofer ISE (see Perovskite Tandem Cell 29.15% Efficiency Record).