Researchers from the Fraunhofer Institute of Solar Energy Systems (ISE) collaborated with industry partners to achieve an efficiency of 22.55% in a perovskite-silicon tandem solar cell measuring over 100 square centimeters.

Funded by the German Federal Ministry of Economic Affairs and Climate Action (BMWK), the project, titled SwiTch, developed interconnection and encapsulation solutions for perovskite-silicon tandem cells using industrial screen-printing metallization.

The experiment aimed to reach the best achievable power conversion efficiency in tandem solar cells of larger size. The best-published efficiency for tandem cells measuring 1 square centimeter under laboratory settings has been 31.3%.

However, Fraunhofer ISE researchers realized that most manufacturing processes used in the laboratory are not suitable for the industrial-scale production of perovskite-silicon tandem solar cells.

According to the department head of photovoltaic modules at Fraunhofer ISE, Holger Neuhaus, “The interconnection and lamination processes had to be understood and adapted in such a way that the perovskite-silicon solar cells can be integrated into the module without damage at low cost, and with long-term stability.”

The solar cell made of perovskite material was stacked atop a conventional silicon solar cell in the experiment. The cells were arranged to enable the enhanced use of the solar spectrum, allowing better capture of sunlight, compared to used pure silicon solar cells.

The positioning of the perovskite solar cell and silicon solar cell establishes improved stability and durability, paving the way for possible industrial production of tandem cells.

The researchers developed the first module prototypes with a peak output of 430 W, for which they performed a detailed analysis of cell-to-module losses while targeting the long-term stability of the tandem photovoltaic modules.

“Efficiencies of over 35% are possible with these tandem solar cells. Laboratory-scale perovskite-silicon tandem solar cells have already overcome the silicon cell’s theoretical upper-efficiency limit of 29.4%, showing promise for even more efficient solar cells in the future,” observed Andreas Bett, director at Fraunhofer ISE.

Earlier this month, scientists at the Swiss Laboratories for Material Science & Technology, Empa, claimed to have developed a low-temperature method using silver to produce a bifacial perovskite-copper indium gallium selenide tandem solar cell. They achieved record efficiencies of 19.8% and 10.9% in the front and rear sides of the bifacial tandem solar cells, respectively.

In June this year, scientists from Fraunhofer ISE’s Center for High-Efficiency Solar Cells claimed to have achieved an energy conversion efficiency of 47.6% in a multijunction solar cell (III-V) using an anti-reflection coating at a concentration of 665 suns.