Fraunhofer Institute Reports New Record Efficiency of 25.9% for Tandem Solar Cells

Researchers at Fraunhofer Institute for Solar Energy Systems ISE announced a new record efficiency of 25.9% for the III-V/Si tandem solar cell grown directly on silicon.

The research and development focus is now on tandem photovoltaics, in which high-performance solar cell materials are brought together in various combinations. This is to use the solar spectrum even more efficiently when converting light into electrical energy.

According to the researchers, the III-V/Si tandem solar cell was assembled on a low-cost silicon substrate for the first time, which can be used as an economical solution for tandem PV. They added that the new technology could also be used for electrolysis, a process to split water into hydrogen and oxygen using electricity to produce hydrogen.

In multi-junction solar cells, two or three different sub-cells piled up on top of each other absorb different portions of the solar spectrum and convert it into electricity. They added that the highest efficiency was achieved by replacing a single thin-layer in a multi-junction cell. Silicon can be used as an absorber as it is more suited for an infrared part of the solar spectrum.


“Not only are we working to make silicon solar cell production more sustainable and cost-effective, but we are also breaking new ground. We are aiming to reach even higher efficiencies using the tried and test silicon in combination with other semiconductors materials and have achieved this in the field of tandem photovoltaics,” said Professor Dr. Stefan Glunz, Division Director of the Photovoltaics Research at Fraunhofer ISE.

According to the press release, researchers at Fraunhofer Institute have been working to develop this technology with the Ilmenau University of Technology, the Philipps University of Marburg, and the company Aixtron since 2007. German Federal Ministry of Education and Research (BMBF) provided funding for these developments as part of the III-V-Si project and the MehrSi project.

In April 2020, Scientists at Helmholtz Zentrum Berlin said they had developed tandem cells that could combine two different semiconductors and convert different parts of the light spectrum into electrical energy. These perovskite CIGS tandem cells were said to be able to achieve a record efficiency of 24.16%.

Mercom earlier reported that researchers at the Australian National University claimed to set a new conversion efficiency record of 27.7% in mechanically-stacked perovskite-silicon tandem cells.

Image Credit: Fraunhofer ISE /Photo: Markus Feifel