Perovskite-silicon tandem solar cells achieve significantly higher efficiencies than silicon solar cells on their own. One particularly attractive method is co-evaporation of the perovskite precursor molecules on top of the silicon subcell. Scientists at HZB have analysed film growth on the nanoscale at BESSY II and found a new way to improve the quality of the perovskite layer: adding a thin seed layer of caesium chloride between the two sub-cells promotes uniform perovskite growth and suppresses the formation of undesired lead iodide at the interface.

Prof. Dr Hatice Mutlu is the new professor of sustainable polymer chemistry at HIPOLE Jena, the Helmholtz Institute for Polymers in Energy Applications. On 17 August 2026, she visited the HZB campus in Berlin-Adlershof including the BESSY II lightsource and discussed future collaboration with researchers and the board of directors.

One 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.

A 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.

A 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.

An international research collaboration has developed a new molecular strategy for controlling one of the most critical interfaces in perovskite solar cells. The resulting solar cells reached a power conversion efficiency of 26.19% in the n i p architecture, together with strong operational stability under prolonged illumination and elevated temperature. The results have been published in the Journal of the American Chemical Society.

Perovskite semiconductors efficiently convert sunlight into electrical energy; they are also inexpensive and extremely lightweight. A team at HZB has developed a triple-junction solar cell comprising different perovskite semiconductors, with a novel bilayer of graphene oxide (GO) and a self-assembled monolayer (SAM) as the hole conductor. This bilayer significantly increases both efficiency and long-term stability. The efficiency of the novel perovskite triple-junction solar cell is 27.3% and shows hardly any decline even after more than 770 hours of operation. The study has been published in the renowned journal Joule.

End of June, the Ukraine Recovery Conference (UCR2026) took place in Gdańsk, Poland. Unlike previous editions, URC2026 introduced a dedicated Energy Platform, jointly organised by the Ministry of Energy of Ukraine and the Ministry of Climate and Environment of Poland, which brought together energy-related discussions, announcements, and side events in one place, increasing the visibility and coordination of key energy topics. Green Deal Ukraїna, an initiative coordinated by HZB, organised three events on the sidelines of URC on research and energy topics as part of the conference.

A Berlin-based team from HZB and Center for the Science of Materials Berlin (CSMB) at the Humboldt-Universität zu Berlin has set a new record for a tandem solar cell. Using a combination of a CIGS semiconductor layer and perovskite, along with several optimised intermediate layers, they were able to convert 25.5% of sunlight into electrical energy. The previous record for this combination of materials and this size of cell stood at 24.6%. The new record has been certified and is visible in the prestigious Solar Cell Efficiency Tables (the "Green Tables"), which serve as the definitive ledger for the global photovoltaic community.

An international research team has demonstrated that the intrinsic disorder of the compound semiconductor CuInSnS₄ can be exploited to influence its optical properties. While the atomic vibrations also sense the local disorder, their response is averaged over many different local environments and therefore appear isotropic, as expected for a cubic crystal. In contrast, the optical excitations, known as excitons, are much more sensitive to the local arrangement of atoms. Surprisingly, they show a direction-dependent optical response even though the average crystal structure is cubic. These findings shed new light on the relationship between disorder and material properties, opening up new options for targeted 'disorder engineering' in optoelectronic and photocatalytic devices.