In order to reduce the formation of pinholes and cracks, we improved the process for making perovskite solar cells.
Scaling up to large scale production
While relatively simple to produce on a small scale in a lab, scaling up perovskite solar cells so they’re useful for real application has been a challenge.
Often, thin film solar cells are fabricated in the lab by spin coating. Spin coating is a deposition method used to deposit uniform thin films to flat substrates. First, coating material is applied to the centre of a substrate. The substrate is then rotated at high speed for a set time. During the set spinning time, centrifugal force causes the coating material to spread and dry, resulting in coating the substrate with a thin, homogeneous film.
While spin coating is a useful deposition technique to use in the lab, industrial scale deposition is usually carried out in very different conditions. As such, spin coating cell fabrication methods are not commonly useful for industrial manufacturing.
Modifying the process
We developed a small scale slot-die coater to fabricate our lab scale perovskite cells using a deposition process that is transferable to industry. Slot die coating is a non-contact deposition technique. It involves delivering a precise volume of material to a substrate by means of a meniscus between a die and the substrate, while the coating die is moved in a controlled manner in relation to the substrate.
The implementation of this type of coater circumvents the use of spin coating as the go-to deposition method for small scale solar cell research. As such, all deposition techniques we use at any point during this research are directly transferable to industrial roll-to-roll production.
Printing and coating of thin films, rather than spin coating films, is preferable due to compatibility with industry. However, during our research it became apparent that coating and printing of electroactive layers often resulted in thin films that had defects in the form of cracks and pinholes. These cracks and pinholes can lower the efficiency of large area solar cells substantially. To combat this, our researchers developed an effective polymer based additive to reduce the amount of cracks and pinholes in the electroactive layers of perovskite solar cells.
CSIRO has patented this additive technology.
A new technique
Since the purpose-built lab scale slot-die coater was installed the pace of research has increased, while the transition from research to potential industry use has been streamlined.
Using a polymer based additive to create pinhole and crack free films is an invaluable contribution to solar research. It also overcomes a major barrier to producing high performance, large area perovskite solar cells.