12 Aug. Longevity test demonstrates efficiency of perovskite solar cells
A unique long-term experiment is underway on the roof of a research building on the Adlershof campus in Berlin: a wide variety of solar cells are being exposed to wind and weather for years and measured in the process. These include perovskite solar cells, which are characterized by high efficiency and low manufacturing costs. The team led by Dr. Carolin Ulbrich and Dr. Mark Khenkin from the Helmholtz Center Berlin (HZB) has evaluated four years of measurement data. The researchers emphasize that this is the longest series of measurements on perovskite cells in outdoor use to date. One finding: standard perovskite solar cells work very well during the summer season, even over several years, but their performance declines somewhat during the darker months.
Several years on the outside
Small perovskite solar cells on a laboratory scale now achieve an efficiency of up to 26.95% under standard test conditions, the researchers report. They are easy to manufacture and inexpensive, and the first perovskite-based solar cells are already on the market. This makes it all the more important to understand the long-term behavior of such perovskite solar cells in outdoor use so that energy yields and service lives can be predicted even more accurately.
At HZB, Ulbrich and her team, supported by the Helmholtz Association-funded Tapas project with the University of Ljubljana, have set up a large outdoor test station: racks equipped with solar cells and measurement technology are installed on the roof. They are exposed to wind and weather all year round. Measurement data from the past four years from small perovskite solar cells encapsulated in glass are now available. The cells were manufactured at HZB by Eva Unger’s team (details on the structure: ITO | 2PACz | Cs0.15FA0.85PbI2.55Br0.45 (band gap of 1.65 eV) | C60 | SnO2 | Cu. ).
Less energy in winter
According to the researchers, the results are encouraging: in the first two summers, peak performance remained virtually unchanged, and between the first and fourth summers, efficiency declined by only about 2% in absolute terms. However, efficiency fell by approximately 30% during the winter months. The team found several reasons for this. At higher latitudes (i.e., at the Berlin site), the spectral distribution of sunlight changes, with more blue components in summer and more red components in winter. However, perovskite solar cells are primarily able to convert the blue components of light into electrical energy. In locations closer to the equator, these spectral shifts are less pronounced, so perovskite solar cells are likely to deliver a more consistent yield throughout the year. “What distinguishes perovskite solar cells from more mature PV technologies is that they often reversibly change their efficiency in the day-night cycle; this property contributes significantly to the strong seasonal fluctuations observed,” says Khenkin.
Original publication
[Advanced Energy Materials (2025): Seasonality in Perovskite Solar Cells: Insights from 4 Years of Outdoor Data, Marko Remec, Mark Khenkin, Ulas Erdil, Quiterie Emery, Gopinath Paramasivam, Eva Unger, Rutger Schlatmann, Steve Albrecht, Marko Topič, Carolin Ulbrich. DOI: 10.1002/aenm.202501906]
Source: www.helmholtz-berlin.de
Image: HZB / Industriefotografie Steinbach