HZB Sets New World Record for CIGS Perovskite Tandem Solar Cells
© G. Farias Basulto / HZB
The tandem cell consists of a combination of CIGS and perovskite and achieves a certified record efficiency of 24.6%. © G. Farias Basulto / HZB
The main components are clearly visible under the scanning electron microscope: granular CIGS crystals on the contact layer, followed by an intermediate layer of aluminium-doped zinc oxide, above which is the extremely thin perovskite layer (black). This is followed by an indium-doped zinc oxide layer and an anti-reflective coating. © HZB
Combining two semiconductor thin films into a tandem solar cell can achieve high efficiencies with a minimal environmental footprint. Teams from HZB and Humboldt University Berlin have now presented a CIGS-perovskite tandem cell that sets a new world record with an efficiency of 24.6%, certified by the independent Fraunhofer Institute for Solar Energy Systems.
Thin-film solar cells require little energy and material to produce and therefore have a very small environmental 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, known as CIGS cells. CIGS thin films can even be applied to flexible substrates.
Now, experts from HZB and Humboldt University Berlin, have developed a new tandem solar cell that combines a bottom cell made of CIGS with a top cell based on perovskite. By improving the contact layers between the top and bottom cells, they were able to increase the efficiency to 24.6 %. This is the current world record, as certified by the Fraunhofer Institute for Solar Energy Systems ISE in Freiburg, Germany.
As always, this record cell was the result of a successful team effort: the top cell was fabricated by TU Berlin master's student Thede Mehlhop under the supervision of Stefan Gall. The perovskite absorber layer was produced in the joint laboratory of HZB and Humboldt University of Berlin. The CIGS sub-cell and contact layers were fabricated by HZB researcher Guillermo Farias Basulto. He also used the high-performance cluster system KOALA, which enables the deposition of perovskites and contact layers in vacuum at HZB.
‘At HZB, we have highly specialised laboratories and experts who are top performers in their fields. With this world record tandem cell, they have once again shown how fruitfully they work together,' says Prof. Rutger Schlatmann, spokesman for the Solar Energy Department at HZB.
The record announced today is not the first world record at HZB: HZB teams have already achieved world record values for tandem solar cells several times, most recently for silicon-perovskite tandem solar cells, but also with the combination CIGS-perovskite.
We are confident that CIGS-perovskite tandem cells can achieve much higher efficiencies, probably more than 30%," says Prof. Rutger Schlatmann.
- Green hydrogen with PEC electrolysers: New insights into transport processesOne method of storing solar energy is to use PEC electrolysers to produce hydrogen. However, scaling up this technology remains challenging. Now, a team at the HZB Institute for Solar Fuels has used 2D fluorescence imaging and particle velocimetry to observe the movement of ions and dissolved gases within the electrolyte during electrolysis. These new insights may prove useful in the development of larger PEC electrolysers.
- New contact material boosts the efficiency of perovskite solar cellsA newly developed material for the electron contact improves the efficiency of single perovskite solar cells and perovskite/silicon tandem solar cells. The new material is based on a carborane molecule. It offers several advantages over the standard material C60, as shown by the study led by Steve Albrecht’s team. The new material has since been patented and is already commercially available.
- BESSY II: New sample environment allows glimpse into thermocatalytic processesA novel measurement cell allows, for the first time, soft and hard X-ray investigations under high pressures of up to 20 bar and temperatures of up to 400°C. This provides new insights into thermocatalytic processes, such as the Fischer-Tropsch synthesis for producing synthetic fuels. The development of the measurement cell is considered a significant achievement within the Care-O-Sene project.