Researchers at the Helmholtz-Zentrum Berlin (HZB) said they have achieved 32.5% conversion efficiency in tandem solar cells, which is the highest ever for this technology and also a world record.

The new tandem solar cell consists of a silicon bottom cell and a perovskite top cell.

European Solar Test Installation (ESTI), a certifying institute in Italy, measured the tandem cell and confirmed the value officially. This is also included in the NREL chart of solar cell technologies.

“This is a really big leap forward that we didn’t foresee a few months ago…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,” Prof. Steve Albrecht said.

Technology modification

The lead authors, Silvia Mariotti, and Eike Köhnen, developed an interface modification to reduce the charge carrier recombination losses and analyzed it in detail to understand the specific properties of the interface modification.

These developments were then successfully implemented in tandem solar cells, and were combined with further optical improvements, the researchers said.

Additionally, many more scientists and technicians helped to develop and fabricate tandem cells to achieve successful results.

Together, both the interface and optical modifications enabled the highest open-circuit voltage — the maximum voltage available from a solar cell — which resulted in the new record efficiency for the tandem technology.

There is an ongoing efficiency development by various research institutes and companies over the last years within the field.

The teams from HZB had claimed to achieve a record value in late 2021 with an efficiency of 29.8% in a tandem solar cell made of perovskite and silicon. The result was certified by Fraunhofer ISE CalLab. The researchers improved upon their earlier conversion efficiency record of 29.15%.

In November, a team of researchers from Northwestern University, the University of Toronto, and the University of Toledo claimed to have developed an all-perovskite tandem solar cell with a conversion efficiency of 27.4%, which is comparable with traditional silicon solar cells.

Image Source: Helmholtz-Zentrum Berlin