Researchers at EPFL’s Photovoltaics and Thin film electronics laboratory and CSEM’s Sustainable Energy Center claim to have set two world records by achieving an efficiency of over 30% for perovskite-on-silicon-tandem solar cells. This path-breaking milestone was independently certified by National Renewable Energy Laboratory (NREL).

Silicon, the most adopted material in solar cell technologies, has a theoretical efficiency limit of 29%. Current efficiencies for this technology stand a little below 27%. The researchers at EPFL and CSEM adopted materials and fabrication techniques to deposit high-quality perovskite layers from solution on a planarized silicon surface, reaching a power conversion efficiency of 30.93% for a 1 cm² solar cell. This was for a planar device architecture and is a world record.

By working on a new version of a hybrid vapor/solution processing technique compatible with textured silicon surfaces, the researchers at EPFL and CSEM have produced a solar cell with a power conversion efficiency of 31.25% on 1 cm². This was for a textured device architecture and is the second world record.

The second record provides a higher current and is compatible with the structure of current industrial solar cells. “We have passed a psychological barrier. We have validated experimentally the high-efficiency potential of perovskite-on-silicon tandems,” said Christophe Ballif, Head of the EPFL Photovoltaics Laboratory and CSEM’s Sustainable energy center.

The 30% efficiency mark had already been achieved with other types of materials, namely III-V semiconductors.  These materials and the processes used to make them are too expensive to sustain the energy transition.

These results will now require further research and development to allow scaling up onto larger surface areas.

The research has received funding from the Swiss Federal Office of Energy, the Swiss National Science Foundation, the European Commission, the Services Industriels de Geneve, and the Advanced Manufacturing Initiative of the ETH domain.

The previous efficiency conversion record of 29.8% for perovskite-on-silicon tandem solar cells was set by a team at the Helmholtz Zentrum Berlin.

In June this year, scientists from the U.S. National Renewable Energy Laboratory (NREL) developed a new tin-lead perovskite tandem cell merging different layers of two chemical compounds achieving a power conversion efficiency (PCE) of 25.5%.

Image credit: CSEM