Helmholtz-Zentrum Berlin für Materialien und Energie (HZB) researchers reported a new world record for tandem solar cells consisting of a silicon bottom cell and a perovskite top cell. The new tandem solar cell converts 32.5 percent of the incident solar radiation into electrical energy.

Photo of the perovskite/silicon tandem solar cell. You can see the active bluish area in the middle of the wafer, which is enclosed by the metallic, silvery electrode. Image Credit: © Johannes Beckedahl/Lea Zimmerman/HZB. Click the press release link for more images.

The certifying institute European Solar Test Installation (ESTI) in Italy measured the tandem cell and officially confirmed this value which is also included in the National Renewable Energy Lab, USA chart of solar cell technologies.

Scientists from HZB could significantly improve on the efficiency of perovskite/silicon tandem solar cells. Prof. Steve Albrecht said, “This is a really big leap forward that we didn’t foresee a few months ago. All the teams involved at HZB, especially the PV Competence Center (PVComB) and the HySPRINT Innovation lab teams have worked together successfully and with passion.”

Interface modifications

Prof Albrecht’s team used an advanced perovskite composition with a very smart interface modification. The lead authors, postdocs Dr. Silvia Mariotti, and Dr. Eike Köhnen in Albrecht’s team, developed an interface modification to reduce charge carrier recombination losses and applied detailed analysis to understand the specific properties of the interface modification. These developments were then successfully implemented in tandem solar cells, and with help of Master’s student Lea Zimmermann, combined with further optical improvements.

In addition, many more scientists and technicians helped to develop and fabricate the tandem cells to achieve this success. Altogether, the interface and optical modifications enabled highest photovoltages (open-circuit voltage) and resulted in the new record efficiency for this fascinating tandem technology.

Fast progress

There is an ongoing efficiency development by various research institutes and companies over the past few years and especially the last month was quite exciting for the field: Various teams from HZB had achieved a record value in late 2021 with an efficiency of 29.8% that was realized by periodic nanotextures. More recently, in summer 2022, the Ecole Polytechnique Fédérale de Lausanne, Switzerland, first reported a certified tandem cell above the 30% barrier at 31.3%, which is a remarkable efficiency jump over the 2021 value.

With the new certified value of 32.5%, the record is again back at HZB. “We are very excited about the new value as it shows that the perovskite/silicon tandem technology is highly promising for contributing to a sustainable energy supply,” said Prof Albrecht.

HZB’s scientific director, Prof. Bernd Rech, emphasized: “At 32.5 percent, the solar cell efficiency of the HZB tandems is now in ranges previously only achieved by expensive III/V semiconductors. The NREL graph clearly shows how spectacular the last two increases from EPFL and HZB really are.”


With exemplary results like this coming in one has to wonder if solar collection research into generating electricity is actually just getting started. At “two deep” and more tech and innovation coming it seems the end of the beginning isn’t here yet.

What may be more important is the suggestion that this technology isn’t as expensive as top of the line silicon models in the III/IV range. In the lab for now, and costs not mentioned one does wonder if this might light up some commercial interest. There is an installed solar industry that has aging cells not much over half the efficiency of this research. Worthwhile motive exists for progress.

Perovskite based cells are not really mass market ready for now, but this news could likely incite a bit more zip into “getting the lead out”, the basic recycling issue perovskite research is working to solve.

Solar electrification’s niche is getting bigger!


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