February 1, 2023

New World Record: Almost 30% Efficiency for Next-Generation Tandem Solar Cells

The world record cell (here in front of the electron storage ring BESSY II) has an area of about one square centimetre, a typical lab size. Credit: Amran Al-Ashouri/ HZB.
3 HZB groups led by Prof. Christiane Becker, Prof. Bernd Stannowski and Prof. Steve Albrecht have jointly handled to increase the efficiency of perovskite silicon tandem solar cells fabricated totally at HZB to a new record worth of 29.80 %. The worth has now been formally certified and is recorded in the NREL-charts. This brings the 30 percent mark within reach.
Todays solar modules are mainly made from silicon, and possibilities for additional boosts in effectiveness have actually already been mainly exploited. But since 2008, the product class of “metal halide perovskites” has actually moved into the focus of research: these semiconductor compounds convert sunlight into electrical energy really well and still use a great deal of room for enhancement. In specific, they can be integrated with silicon solar cells to tandem solar batteries that use sunshine far more efficiently.
A race for records.
At HZB, a number of groups have been working intensively since 2015 on both the perovskite semiconductors and silicon technologies and the mix of both into ingenious tandem solar cells. In January 2020, HZB had achieved a record 29.15 % for a perovskite silicon tandem solar cell and published the operate in the journal Science. Prior to Christmas 2020, the company Oxford PV was able to announce a licensed effectiveness of 29.52 %. Considering that then, the interesting race for new records has actually been on. “An effectiveness of 30 % is like a mental limit for this remarkable new technology which might change the photovoltaic market in the near future,” explains Steve Albrecht, who is working on perovskite thin films at the HySPRINT lab at HZB. Bernd Stannowski, group leader for silicon technology, includes: “I would particularly highlight the great cooperation between the different groups and institutes at HZB. This is how we managed to establish these brand-new tandem solar batteries entirely at HZB and when again get the world record.”.

Three HZB teams led by Prof. Christiane Becker, Prof. Bernd Stannowski and Prof. Steve Albrecht have actually collectively managed to increase the effectiveness of perovskite silicon tandem solar cells made entirely at HZB to a new record value of 29.80 %. In particular, they can be combined with silicon solar cells to tandem solar cells that use sunlight much more effectively.
In January 2020, HZB had achieved a record 29.15 % for a perovskite silicon tandem solar cell and published the work in the journal Science. Now came the main confirmation by Fraunhofer ISE CalLab: “Our brand-new perovskite silicon tandem solar cells were separately accredited with a world record performance of 29.80 %,” states a pleased Christiane Becker, a specialist on nanostructures in solar cells and their results on the electrical and optical residential or commercial properties.
For the new work, Dr. Philipp Tockhorn (Albrecht group) and doctoral trainee Johannes Sutter (Becker group) investigated how nanostructures at different interfaces affect the performance of a tandem solar cell, consisting of a perovskite solar cell on top of a silicon solar cell.

The perovskite silicon tandem cell is based on 2 developments: A nanotextured front side (left) and a rear end with dielectric reflector (right). Credit: Alexandros Cruz/ HZB.
Official accreditation.
The recent research study and advancement focus was on the optical improvement of the silicon heterojunction bottom cell. A nanotextured front side and a dielectric back reflector were added. Now came the official verification by Fraunhofer ISE CalLab: “Our brand-new perovskite silicon tandem solar batteries were individually certified with a world record performance of 29.80 %,” states a thrilled Christiane Becker, a professional on nanostructures in solar batteries and their impacts on the electrical and optical properties.
Nanotextured silicon.
For the new work, Dr. Philipp Tockhorn (Albrecht group) and doctoral trainee Johannes Sutter (Becker group) investigated how nanostructures at various user interfaces affect the efficiency of a tandem solar cell, consisting of a perovskite solar cell on top of a silicon solar cell. They produced perovskite silicon tandem solar cells with different textures: “Even the nanotexturing on one side enhances the light absorption and enables a greater photocurrent compared to a flat recommendation,” says Sutter.
Dielectric reflector.
Improvements were also made to the back side of the tandem solar battery, which is designed to show infrared light back into the silicon absorber. “By using a dielectric reflector, we were able to utilize this part of the sunshine more efficiently, resulting in a higher photocurrent,” states Dr. Alexandros Cruz Bournazou (Stannowski group).
Outlook is bright.
The outcomes pave the way for further improvements. The simulations recommend that the performance could be increased even further by nanostructuring the absorber layers on both sides. The researchers are encouraged that a performance of well over 30 % could be possible quickly. The race is on.
Recommendation: “Monolithic perovskite/silicon tandem solar cell with >> 29% performance by enhanced hole extraction” by Amran Al-Ashouri, Eike Köhnen, Bor Li, Artiom Magomedov, Hannes Hempel, Pietro Caprioglio, José A. Márquez, Anna Belen Morales Vilches, Ernestas Kasparavicius, Joel A. Smith, Nga Phung, Dorothee Menzel, Max Grischek, Lukas Kegelmann, Dieter Skroblin, Christian Gollwitzer, Tadas Malinauskas, Marko Jošt, Gašper Matic, Bernd Rech, Rutger Schlatmann, Marko Topic, Lars Korte, Antonio Abate, Bernd Stannowski, Dieter Neher, Martin Stolterfoht, Thomas Unold, Vytautas Getautis and Steve Albrecht, 11 December 2021, Science.DOI: 10.1126/ science.abd4016.

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