Extensive research in recent years has proven that tandem solar cells (TSCs) – a double semiconductor layer capable of absorbing the widest solar spectrum – are far more efficient at generating electricity than conventional single-layered cells. While conventional cells are now approaching their practical maximum level of 27 percent efficiency, tandem perovskite cells are expected to exceed the 30 percent mark in the next few years. They are also lightweight and highly flexible.
Now it’s time to fast-track the technology to ready it for market. That’s why the Federal Ministry of Economic Affairs and Climate Action (BMWK) has funded the construction of two state-of-the-art research plants for producing TSCs at the Centre for Solar Energy and Hydrogen Research Baden-Württemberg (ZSW). Both facilities are now up and running –one makes thin-film perovskite solar cells for absorbing visible light; the other makes CIGS (cells made of copper, indium, gallium and selenium) for the bottom layer which converts light in the near-infrared spectrum.
Both types can easily be combined with other solar cells: for example, perovskite and CIGS, double perovskites or perovskite and silicon. In practice, this means silicon cell manufacturers can now have their products converted into TSCs at ZSW in an ultra-clean laboratory using a vacuum-coating process. The institute is also breaking new ground with its fabrication techniques including a vapour-deposited organic electron conductor layering process.
“Excellent conditions are now in place... to develop tandem solar cells, particularly in terms of the process technology for manufacturing solar cells in a vacuum under ultra-clean lab conditions,” says Dr Jan-Philipp Becker, the new head of the ZSW's Photovoltaics: Materials Research department in a . “We want to use these assets to explore the technology’s physical boundaries.”