Tokyo (SCCIJ) – Swiss researchers have pushed the efficiency of tandem solar cells beyond the 30%-barrier while using low-cost materials and processes. These results will boost high-efficiency photovoltaics and pave the way toward even more competitive solar electricity generation.
The perovskite-on-silicon tandem cells are either flat or textured on their front side (Credit: D. Türkay/C. Wolff (EPFL)).
Official certification
The Swiss Federal Laboratories for Materials Science and Technology (Empa) and the Photovoltaics and Thin Film Electronics Laboratory of the Swiss Federal Institute of Technology in Lausanne (EPFL) joined forces to develop these perovskite-on-silicon-tandem solar cells. The National Renewable Energy Laboratory (NREL) in the United States certified the measured efficiency.
Other types of solar cell materials, namely III-V semiconductors, have already achieved the 30% efficiency mark. However, the used materials and the processes make them a thousand times more expensive than silicon solar cells.
Such cells have a theoretical efficiency limit of around 29%. Current efficiencies for this technology stand slightly below 27%. Materials called halide perovskites have been identified as an ideal tandem partner for silicon.
“Our results are the first to show that the 30% psychological barrier can be overcome using low-cost materials and processes, which should open new perspectives for the future of photovoltaics,” says Christophe Ballif, Head of the EPFL Photovoltaics Laboratory and CSEM’s Sustainable Energy Center.
Double strategy
The researchers from Neuchâtel have succeeded in improving the efficiency of two kinds of perovskite-on-silicon tandems. Firstly, they adapted 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.
Secondly, by working on a new version of a hybrid vapor/solution processing technique compatible with textured silicon surfaces, they have produced a solar cell with a power conversion efficiency of 31.25%. These results constitute two new world records: one for the planar and one for the textured device architecture.
The latter approach provides a higher current and is compatible with the structure of current industrial silicon solar cells. The previous efficiency conversion record for perovskite-on-silicon tandem solar cells of 29.8% was set in 2021 by a team at the Helmholtz Zentrum Berlin.
“These high-efficiency results will now require further R&D to allow their scaling up onto larger surface areas and to ensure that these new cells can maintain a stable power output on our rooftops and elsewhere over a standard lifetime,” notes Quentin Jeangros of CSEM.
Text: CSEM (editing by SCCIJ)
