HZB Newsroom

Perovskite solar cells are widely regarded as the next generation photovoltaic technology. However, they are not yet stable enough in the long term for widespread commercial use. One reason for this is migrating ions, which cause degradation of the semiconducting material over time. A team from HZB and the University of Potsdam has now investigated the ion density in four different, widely used perovskite compounds and discovered significant differences. Tin perovskite semiconductors produced with an alternative solvent had a particular low ion density — only one tenth that of lead perovskite semiconductors. This suggests that tin-based perovskites could be used to make solar cells that are not only really environmentally friendly but also very stable.

Perovskite solar cells are inexpensive to produce and generate a high amount of electric power per surface area. However, they are not yet stable enough, losing efficiency more rapidly than the silicon market standard. Now, an international team led by Prof. Dr. Antonio Abate has dramatically increased their stability by applying a novel coating to the interface between the surface of the perovskite and the top contact layer. This has even boosted efficiency to almost 27%, which represents the state-of-the-art. After 1,200 hours of continuous operation under standard illumination, no decrease in efficiency was observed. The study involved research teams from China, Italy, Switzerland and Germany and has been published in Nature Photonics.

Photovoltaics is the leading technology in the transition to clean energy. However, traditional silicon-based solar technology has reached its efficiency limit. Therefore, a HZB-team has developed a perovskite-based multi-junction cell architecture. For this, Kevin J. Prince and Siddhartha Garud received the Helmholtz-Zentrum Berlin's (HZB) Technology Transfer Prize of 5,000 euros.

Tin perovskite solar cells are not only non-toxic, but also potentially more stable than lead-containing perovskite solar cells. However, they are also significantly less efficient. Now, an international team has succeeded in reducing losses in the lower contact layer of tin perovskite solar cells: The scienstists identified chemical compounds that self-assemble into a molecular layer that fits very well with the lattice structure of tin perovskites. On this monolayer, tin perovskite with excellent optoelectronic quality can be grown, which increases the performance of the solar cell.

Scientists at HZB run a long-term experiment on the roof of a building at the Adlershof campus. They expose a wide variety of solar cells to the weather conditions, recording their performance over a period of years. These include perovskite solar cells, a new photovoltaic material offering high efficiency and low manufacturing costs. Dr Carolin Ulbrich and Dr Mark Khenkin evaluated four years of data and presented their findings in Advanced Energy Materials. This is the longest series of measurements on perovskite cells in outdoor use to date. The scientists found that standard perovskite solar cells perform very well during the summer months, even over several years, but decline in efficiency during the darker months.

Silvia Mariotti starts building up the new Helmholtz Young Investigator Group ‘Perovskite-based multi-junction solar cells’. The perovskite expert, who was previously based at Okinawa University in Japan, aims to advance the development of multi-junction solar cells made from different perovskite layers.