Perovskite solar cells: TEAM PV develops reproducibility and comparability
Perovskite materials for photovoltaic applications come in many shades, reflecting their huge variety of optical properties. This makes them uniquely fit to be combined with other materials in multijunction solar cells. © M. Setzpfandt/HZB
At HZB several labs are dedicated to perovskite research. Here different compositions of the material can be prepared. © M. Setzpfandt/HZB
The HZB runs a testing facility in order to observe different perovskite solar cells in real life conditions. © HZB
Ten teams at Helmholtz-Zentrum Berlin are building a long-term international alliance to converge practices and develop reproducibility and comparability in perovskite materials. The TEAM PV project is funded by the Federal Ministry of Education and Research (BMBF), Germany.
Solar energy is already the cheapest way to generate electricity in many parts of the world. But the world needs much higher efficiency solar modules to power demanding sectors such as electric vehicles, steel production, and AI. Likely the only option for increasing efficiency within the next decade is halide perovskites, a new class of materials that has been the subject of intensive research in the last decade. And while the silicon modules that dominate the market today are mainly produced in China, production facilities for halide perovskite cells could also be set up in Europe and the US, de-risking supply chains.
However, the road from the laboratory to mass production is long and there are still a number of hurdles to overcome. "The central goal is to increase the manufacturability, stability, and reliability of perovskite-based technologies. We urgently need common protocols to reliably compare diverse global developments in these novel materials and also to predict their service life," says Dr Siddhartha Garud, who drives the management of the TEAM PV project at HZB. Within this project, HZB aims to converge best practices in fabrication and analyses together with the National Renewable Energy Lab NREL, the University of Colorado Boulder and Humboldt-Universität zu Berlin.
One of the main questions is how the stability determined in a laboratory will behave under real conditions in a field. Another focus will be on machine learning methods to navigate this extremely vast class of materials and devices. The participating teams will work closely together to further develop the fabrication and analysis of perovskite thin films and full devices.
The BMBF is providing a total of €4 million in funding for the TEAM PV project for tools, personnel and researcher exchanges. "We want to establish a long-term partnership in photovoltaics with sustained researcher exchanges and also make it a starting point for further collaborations between the Helmholtz Association and National Labs and top Universities in the U.S.", Garud says.
- Magnetic imaging: Micro-flowers increase the local magnetic fieldMaterials with magnetic nanostructures have many potential applications such as in spintronics. To explore such materials, nanoscale magnetic-sensitive imaging techniques are very useful, but up to now only weak magnetic fields could be applied during the imaging process. Now an international collaboration led by Dr. Sergio Valencia, HZB, has developed an approach that overcomes this limitation. The team designed tiny magnetic flux concentrators (MFCs), into which the sample is placed. The geometry of the MFCs resembles a flower with a number of petals which focus the applied magnetic field into its center. This greatly expands the magnetic field range available during imaging, and so the range of magnetic systems that can be investigated. The micro-flowers, enhancing magnetic fields locally, can find application in different nanometric magnetic microscopy techniques.
- CIGS-perovskite tandem cell achieves record efficiency of 25.5 %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.
- Disorder creates new properties in compound semiconductorsAn 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.