Solar cells made of perovskites and copper indium diselinide can be flexibly attached to vehicles or wearables. KIT researchers have now achieved record efficiency for tandem cells.
The efficiency of solar cells can be increased by stacking two or more cells to form so-called tandems. By combining perovskites with materials such as copper indium diselenide (CIS) or copper indium gallium diselenide (CIGS), flexible solar cells are created that can also be folded and rolled. In the EU project Percistand, researchers from the Karlsruhe Institute of Technology (KIT) and partners have produced perovskite/CIS tandem solar cells with a peak efficiency of 24.9 %. According to the university, this is the highest efficiency ever achieved for this technology.
Crucial to the development was the reduction in the amount of gallium and the associated narrow band gap of about one electron volt in the bottom solar cell, which is close to the physical optimum. Because of the narrow band gap, which indicates what part of the sunlight spectrum the cell absorbs, the scientists were able to produce the top perovskite solar cell with a low bromine content, making it more efficient and stable.