In the future, tandem solar cells will far exceed the maximum efficiency rates of today’s conventional silicon solar cells at around 32 percent. Scientists already know that stacking a perovskite cell on top of a conventional silicon photovoltaic (PV) cell makes more effective use of the solar spectrum – and efficiency rates of 35 percent have been achieved.

For the last two years, researchers at the Fraunhofer Institute for Solar Energy Systems (ISE) have been working simultaneously on four projects to bring the production of tandem perovskite-silicon PV technology to market, with support from the German Federal Ministry of Economic Affairs and Climate Action.

At the cell level, in the projects MaNiTU and PrEs-to, the researchers succeeded in scaling up perovskite-silicon cells from laboratory size (1cm²) to wafer size (around 1M²). While some efficiency was lost in the process, the scientists are confident they can close the gap. “We have succeeded in achieving a certified efficiency of 22.5 percent...with an area of more than 100cm² and with industrial screen-printing metallisation. Our aim is now to realise the high efficiencies of our small laboratory cells on large-area cells using scalable fabrication methods,” summarises Dr Patricia Schulze in a press release.

In the joint project SwiTch, Fraunhofer ISE worked with industrial partners to develop interconnection and encapsulation techniques for full modules. “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,” explains Dr Holger Neuhaus, head of Photovoltaic Modules. The first prototypes with an output of 430 watts peak have been produced.

Finally, in project SALTO, ISE verified the use of a new kind of low-temperature interconnection technology called SmartWire (SWTC™), developed by solar module company Meyer Burger, as a more effective alternative to soldering.