HZB sets another world record for CIGS-Pero tandem solar cells
The tandem cell combines CIGS and perovskite and achieves a certified record efficiency of 24.6%. © G. Farias Basulto / HZB
The most important components are clearly visible under the scanning electron microscope: on the contact layer there are granular CIGS crystals, on top of which there is an intermediate layer of aluminum-doped zinc oxide, on top of which lies the extremely thin perovskite layer (black). On top of this there is an indium-doped zinc oxide layer and an anti-reflective coating. © HZB
By combining two semiconductor thin films to form a tandem solar cell, high efficiencies can be achieved with a minimal ecological footprint. Teams from the HZB and the Humboldt University of Berlin have now presented a tandem cell made of CIGS and perovskite that holds the new world record with an efficiency of 24.6%. This value was certified by the Fraunhofer Institute for Solar Energy Systems ISE.
Thin-film solar cells require little energy and material to produce and are therefore characterized by a very small ecological footprint. In addition to the well-known and market-leading silicon solar cells, there are also thin-film solar cells, e.g. based on copper, indium, gallium and selenium, so-called CIGS cells. CIGS thin films can even be applied to flexible substrates.
Now experts at the HZB, together with the Humboldt University of Berlin, have developed a new tandem solar cell that combines a lower cell made of CIGS with an upper cell based on perovskite. By improving the contact layers between the upper and lower cells, it was possible to increase the efficiency to 24.6%. This is the current world record, and the value was certified by the Fraunhofer Institute for Solar Energy Systems ISE in Freiburg.
As always, this record value could only be achieved through a successful team effort: The top cell was produced by TU Berlin master's student Thede Mehlhop, supervised by Stefan Gall. The perovskite absorber layer comes from the joint laboratory of the HZB and the Humboldt University of Berlin. The CIGS sub-cell and the contact layers were produced by HZB researcher Guillermo Farias Basulto. He also used the powerful KOALA cluster system, which enables the coating of perovskites and contact layers in a vacuum at the HZB.
"At the HZB, we have highly specialized laboratories and experts who deliver top performance in their field. With this world-record tandem cell, they have once again shown how productively they work together," says Prof. Rutger Schlatmann, spokesperson for the Solar Energy Department at the HZB.
The record now reported is not the first world record at HZB: HZB teams have already achieved world record values several times with tandem solar cells, most recently with silicon-perovskite tandem solar cells, but also with the CIGS-perovskite combination.
“We are confident that CIGS-perovskite tandem cells can achieve much higher efficiencies, most likely over 30%,” says Prof. Rutger Schlatmann.
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