To overcome global energy challenges and fight the looming environmental crisis, researchers around the world investigate new materials for converting sunlight into electricity. Some of the most promising candidates for high-efficiency low-cost solar cell applications are based on lead halide perovskite (LHP) semiconductors. Despite record-breaking solar cell prototypes, the microscopic origin of the surprisingly excellent optoelectronic performance of this material class is still not completely understood. Now, an international team of physicists and chemists from Fritz Haber Institute of the Max Planck Society, École Polytechnique in Paris, Columbia University in New York, and the Free University in Berlin demonstrated laser-driven control of fundamental motions of the LHP atomic lattice. By applying a sudden electric field spike faster than a trillionth of a second (picosecond) in the form of a single light cycle of far-infrared Terahertz radiation, the investigators unveiled the ultrafast lattice response, which might contribute to a dynamic protection mechanism for electric charges. This precise control over the atomic twist motions will allow to create novel non-equilibrium material properties, potentially providing hints for designing the solar cell material of the future.

Surfactants play an important role in every day life, for instance as major components in soaps.  Since they feature hydrophilic and hydrophobic parts in their structure, they accumulate at water interfaces with air and can there influence the rate of evaporation of the solution or the efficiency with which gas molecules are taken up by the solution, a process that is for instance important for the incorporation of carbon dioxide into the oceans. How surfactants arrange themselves at the interface of water with air is an intriguing question that has fascinated scientist for centuries, going back to Benjamin Franklin who noted the calming effect of cooking oil on the surface of water, and Agnes Pockels who did some of the first systematic experiments on the subject in the late 19^th century. The question of the arrangement of surfactant molecules at the water-air interface is not easy to answer since a close look at the very skin of liquid water requires methods that hone in on the outer layers of water, where surfactant molecules are located in a layer with a thickness of only a few billionths of a meter.

Photovoltaics, the conversion of light to electricity, is a key technology for sustainable energy. Since the days of Max Planck and Albert Einstein, we know that light as well as electricity are quantized, meaning they come in tiny packets called photons and electrons. In a solar cell, the energy of a single photon is transferred to a single electron of the material, but no more than one. Only a few molecular materials like pentacene are an exception, where one photon is converted to two electrons instead. This excitation doubling, which is called exciton fission, could be extremely useful for high-efficiency photovoltaics, specifically to upgrade the dominant technology based on silicon. A team of researchers at the Fritz Haber Institute of the Max Planck Society, the Technical University of Berlin, and the Julius-Maximilians-Universität of Würzburg have now deciphered the first step of this process by recording an ultrafast movie of the photon-to-electricity conversion process, resolving a decades-old debate about the mechanism of the process.

The CatLab project now presented itself very successfully at the international conference on "Challenges on Renewable Energy Storage" in Liblice near Prague. In addition to the FHI, the Helmholtz Centre Berlin and the Max Planck Institute for Chemical Energy Conversion are also involved in the joint catalysis research for better use of green hydrogen.

The application process for the 13th THz Young Scientists Meeting is open. The event will take place from 14th - 15th September in Berlin.