Perovskite Solar Cells: paving the way for rational ink design for industrial-scale manufacturing
Schematic illustration: the solvants (ink) are used to produce a thin film of polycrystalline perovskite. © HZB
For the production of high-quality metal-halide perovskite thin-films for large area photovoltaic modules often optimized inks are used which contain a mixture of solvents. An HZB team at BESSY II has now analysed the crystallisation processes within such mixtures. A model has also been developed to assess the kinetics of the crystallisation processes for different solvent mixtures. The results are of high importance for the further development of perovskite inks for industrial-scale deposition processes of these semiconductors.
Hybrid organic perovskite semiconductors are a class of materials for solar cells, which promise high efficiencies at low costs. They can be processed from precursor solutions that upon evaporation on a substrate form a polycrystalline thin film. Simple manufacturing processes, such as spin coating a precursor solution, often only lead to good results on a laboratory scale, i.e. for very small samples.
Printing large areas
For the production of larger area photovoltaic modules, the team of Dr. Eva Unger develops printing and coating processes in which the perovskite semiconductor is processed from inks containing the precursors dissolved in solvents. The composition of the ink determines the material formation mechanism with the solvent affecting the process by its rheological properties, evaporation rate and participation in intermediate phases. "Our research question in this project was: How can we rationalize the difference in crystallization kinetics when using different solvents," explains Unger, who heads the Young Investigator Group Hybrid Materials Formation and Scaling.
Different evaporation rates
In solvents with only one component, the crystallization process is determined by the evaporation rate. "In mixtures of solvents, evaporation is dominated by the most volatile component that evaporates the fastest. This changes the ratio of solvents that are present upon crystallization", says Dr. Oleksandra Shargaieva, postdoc in Unger's team.
Crystallization analyzed at BESSY II
At the KMC-2 beamline of BESSY II, she was able to analyse the formation of the perovskite semiconductor and crystalline intermediate phases incorporating solvent molecules during the evaporation of the solvents. “I found that the formation mechanism critically depends both on the solvents evaporation rate and binding strength to the lead-halide. “These insights will help to predict the kinetics of crystallization processes of the perovskite thin film for different solvent combinations based on the properties of the precursor solutions”, says Shargaieva.
"There is still a lack of systematic knowledge when scaling up from laboratory scale to industrial area sizes. With these results we pave the way for further ink design to enable industrial-scale manufacturing or perovskite thin films of high quality”, says Unger.
- Susanne Nies appointed to EU advisory group on Green DealDr. Susanne Nies heads the Green Deal Ukraina project at HZB, which aims to support the development of a sustainable energy system in Ukraine. The energy expert has now also been appointed to the European Commission's scientific advisory group to comment on regulatory burdens in connection with the net-zero target (DG GROW).
- The future of corals – what X-rays can tell usThis summer, it was all over the media. Driven by the climate crisis, the oceans have now also passed a critical point, the absorption of CO2 is making the oceans increasingly acidic. The shells of certain sea snails are already showing the first signs of damage. But also the skeleton structures of coral reefs are deteriorating in more acidic conditions. This is especially concerning given that corals are already suffering from marine heatwaves and pollution, which are leading to bleaching and finally to the death of entire reefs worldwide. But how exactly does ocean acidification affect reef structures?
Prof. Dr. Tali Mass, a marine biologist from the University of Haifa, Israel, is an expert on stony corals. Together with Prof. Dr. Paul Zaslansky, X-ray imaging expert from Charité Berlin, she investigated at BESSY II the skeleton formation in baby corals, raised under different pH conditions. Antonia Rötger spoke online with the two experts about the results of their recent study and the future of coral reefs.
- Long-term stability for perovskite solar cells: a big step forwardPerovskite 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.