Scientists at Helmholtz Zentrum Berlin (HZB) have developed tandem cells that combine two different semiconductors and convert different parts of the light spectrum into electrical energy. The new perovskite CIGS tandem cell achieves a record efficiency of 24.16%.

The metal halide perovskite compounds mainly convert visible parts of the spectrum, whereas, CIGS semiconductors deal with the infrared light.

As the name suggests, CIGS cells are made of copper, indium, gallium, and selenium, and these can be deposited as thin films with a total thickness of only 3 to 4 micrometers. The perovskite layers are even much thinner at 0.5 micrometers. The tandem cells, which are a combination of CIGS and perovskite cells, have thickness well below the five-micrometer level, and this could lead to the production of flexible solar modules.

Talking about this latest combination, Steve Albrecht of HZB, said, “This combination is also extremely lightweight and stable against irradiation, and could be suitable for applications in satellite technology in space.”

Speaking on the tandem cells, Christian Kaufmann from PVcomB at HZB, commented, “This time, we have connected the bottom cell (CIGS) directly with the top cell (perovskite), so that the tandem cell has only two electrical contacts, so-called terminals. Especially the introduction of rubidium has significantly improved the CIGS absorber material.”

By using the new perovskite CIGS tandem cells, the team has achieved an efficiency of 24.16%, and it has been officially certified the CalLab of the Fraunhofer Institute for Solar Energy Systems (ISE).

The new ‘2 Terminal’ tandem cells have been made of CIGS and perovskite cells. The National Renewable Energy Lab (NREL), USA, has created a new branch on the famous NREL chart for this purpose. The chart has been keeping track of cell efficiencies for all solar types since 1976, and perovskite compounds were included since 2013.

Recently, several new world records using perovskite cells in combination with inorganic semiconductors have been issued by HZB.

Recently, the researchers at the NREL have come up with a technology that could sequester the minuscule quantity of lead used in developing perovskite solar cells. This development might mark the beginning of an efficient emerging photovoltaic technology.

Earlier, Mercom had reported that combining thin-film solar modules based on perovskite semiconductors with semiconductors made of CIGS, solar module technology could cross the 30% efficiency mark, according to a study conducted by the Karls-ruhe Institute of Technology (KIT), Nice Solar Energy, and the Centre for Solar Energy and Hydrogen Research Baden-Württemberg (ZSW).

Image credit: HZB