SOLAR CELLS UK study reports highest ever efficiency for printed perovskite cells
A team from the Swansea University in Wales, UK claim to have achieved the highest ever efficiency recorded for full roll-to-roll printed perovskite solar cells.
A team of researchers from the UK’s Swansea University claim that they have used a roll-to-roll fabrication method to coproduce four layers of slot-die coated photovoltaic solar cells (PSCs) with the highest efficiency levels ever recorded. If true, this achievement could go down in history as a major milestone, paving the way for more economical and efficient methods for solar energy generation in the years to come.
Record-breaking efficiency levels
The PSCs printed using the Swansea team’s roll-to-roll method are said to provide a stable power output of 12.2 percent, the highest efficiency for four layers of PSCs fabricated by using this method to date. When compared to silicon photovoltaic (PV) solar cells, which require high temperatures and vacuum depositions to produce, PSCs can be solution-processed at much lower temperatures which not only drastically cuts manufacturing costs but also makes it possible to use plastic substrates, which would otherwise be destroyed, and create flexible solar cells.
According to the Swansea team’s research, it is this solution-process method that provides the opportunity to apply well-developed printing and coating techniques to their PSCs and use roll-to-roll methods to fabricate four layers of printed PSCs. These include screen printing, inkjet printing, and slot-die and spray coating.
In an official statement, lead researcher Rahul Patidar said: “Perovskite solar cells aim to increase the efficiency and lower the cost of traditional solar energy generation. They have the potential to be highly efficient and relatively cheap to manufacture, so the aim is to improve fabrication methods for upscaling. This study signifies the next step towards commercialisation.”
Slot-die coating PSCs
By using a slot-die coating method, the researchers were able to control the thickness of the wet film prior to coating. It is also very efficient in terms of materials usage because it results in minimal loss in contrast to spray coating or screen printing.
Further efficiencies were achieved through the use of an acetonitrile-based system which features a rheological advantage due to low viscosity and surface tension. This results in better coatings. Without this system, the Swansea team would have had to use a significantly more expensive process that uses toxic solvents at an industrial scale. Along with this system, a ternary blend of high workspace exposure limit solvents was introduced. These replaced chlorobenzene for the deposition of hole transport material.
There are still challenges to overcome, however.
An entire solar cell for a selected architecture requires five layers of coating. But in this study, four layers were coated via the slot-die technique, with the top contact formed using thermal evaporation. Coating the fifth layer (top contact) through slot-die coating without damaging any of the other layers is currently not possible. If this problem is solved, it may become possible to manufacture a fully roll-to-roll printed perovskite solar cell, the researchers say.