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.
- Porous Radical Organic framework improves lithium-sulphur batteriesA team led by Prof. Yan Lu, HZB, and Prof. Arne Thomas, Technical University of Berlin, has developed a material that enhances the capacity and stability of lithium-sulphur batteries. The material is based on polymers that form a framework with open pores (known as radical-cationic covalent organic frameworks or COFs). Catalytically accelerated reactions take place in these pores, firmly trapping polysulphides, which would shorten the battery life. Some of the experimental analyses were conducted at the BAMline at BESSY II.
- Metallic nanocatalysts: what really happens during catalysisUsing a combination of spectromicroscopy at BESSY II and microscopic analyses at DESY's NanoLab, a team has gained new insights into the chemical behaviour of nanocatalysts during catalysis. The nanoparticles consisted of a platinum core with a rhodium shell. This configuration allows a better understanding of structural changes in, for example, rhodium-platinum catalysts for emission control. The results show that under typical catalytic conditions, some of the rhodium in the shell can diffuse into the interior of the nanoparticles. However, most of it remains on the surface and oxidises. This process is strongly dependent on the surface orientation of the nanoparticle facets.
- Shedding light on insulators: how light pulses unfreeze electronsMetal oxides are abundant in nature and central to technologies such as photocatalysis and photovoltaics. Yet, many suffer from poor electrical conduction, caused by strong repulsion between electrons in neighboring metal atoms. Researchers at HZB and partner institutions have shown that light pulses can temporarily weaken these repulsive forces, lowering the energy required for electrons mobility, inducing a metal-like behavior. This discovery offers a new way to manipulate material properties with light, with high potential to more efficient light-based devices.