The semiconductor perovskite is seen as the new hope for bringing the production price of solar cells down below that of the silicon used to date. Empa is developing new manufacturing processes to produce perovskite solar cells not only more cheaply, but also faster and make them fit for industrial use.
Today, perovskite solar cells achieve an efficiency comparable to that of a conventional silicon cell. However, due to their structure and the materials used, they are very sensitive to moisture, oxygen, heat, UV light and mechanical stress. This makes the cell less durable. By developing a cell with a framework of oxides and carbon, these disadvantages could be eliminated, but the idea was not yet ready for the market.
Today, the so-called slot die process is used to produce this new type of perovskite cell. The material layer is applied to a glass layer and then structured by removing excess material using a laser. The new coating process not only enables faster coating, but also allows the thickness of the individual layers to be defined more precisely. In future, the slot die process will make it possible to coat meter-long strips relatively easily and quickly. The increased coating speed is also the central element in the possible industrialization of perovskite cell production.
A total of five layers of different materials, including titanium oxide, zirconium oxide and graphite, are required for such a cell. While the previous screen printing process required the layers to be dried and sintered (i.e. compacted) individually, which takes a lot of time and energy, the slot die process allows all layers to be applied directly one after the other and sintered together. This new process can be used to print seven times faster than the previous screen printing method. The perovskite solar cell is given the final touch by applying the perovskite absorber using inkjet printing at Empa's Coating Competence Center, a process known as infiltration. In this process, the perovskite is not applied to the substrate as a solid layer as before, but seeps through all the porous sub-layers of the solar cell to the bottom.
Empa, www.empa.ch
