21st December 2022 New record solar cell efficiency A new world record solar cell efficiency for a silicon-perovskite tandem solar cell has been achieved, with scientists in Germany converting 32.5% of sunlight into electrical energy.
The current world record of tandem solar cells consisting of a silicon bottom cell and a perovskite top cell has once again been broken by Helmholtz-Zentrum Berlin für Materialien und Energie (HZB), Germany. A team created a new tandem solar cell converting 32.5% of incident solar radiation into electrical energy. The certifying institute, European Solar Test Installation in Italy, measured the tandem cell and officially confirmed this value. It has also been included in the NREL chart of solar cell technologies (pictured below), maintained by the National Renewable Energy Lab, USA. The breakthrough could significantly improve on the efficiency of commercial perovskite/silicon tandem solar cells.
"This is a really big leap forward that we didn't foresee a few months ago," says Prof. Steve Albrecht. "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." His team used an advanced perovskite composition with a very smart interface modification. Lead authors, postdocs Dr. Silvia Mariotti, and Dr. Eike Köhnen in Albrecht's team, developed a way of reducing 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 Masters 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.
There is an ongoing efficiency drive by various research institutes and companies, which over the last few years and especially the last month has been quite exciting for the field: teams from HZB had achieved a record value in late 2021 with an efficiency of 29.8% that was realised 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," says Albrecht. HZB's scientific director, Prof. Bernd Rech, emphasises: "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."
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