KAUST team roll on with solar perovskite production

According to the team at King Abdullah University of Science and Technology (KAUST), they were also able to coat the ink onto textured silicon, creating the ‘very first slot-die coated silicon-perovskite monolithic tandem solar cell’ with a claimed efficiency of 23.8 per cent. It is hoped that their ink formulation could help to turn PSCs into commercially successful products.

Swansea team on a roll with printed perovskite solar cells

“PSCs have shown a lot of promise in lab-scale work over the last decade,” said Anand Subbiah, a postdoctoral researcher in Stefaan De Wolf’s lab at KAUST. “As a community, we need to start looking at the stability and scalability of PSC technology.”

PSCs made in research labs are typically made by spin-coating, which is unsuited to mass manufacture. Slot-die-coating, in contrast, is a technique used industrially for almost 70 years. In a statement, Subbiah said the process involves continuously and precisely forcing an ink through a narrow slit that is moved across the substrate to form a continuous film. “This high-throughput technique would allow for roll-to-roll fabrication, similar to printing newspapers,” he said.

There were several challenges faced by the team in producing high-efficiency slot-die coated PSCs, they confirmed. Some of the best-performing spin-coated PSCs combine the perovskite with a polytriarylamine (PTAA) transport layer, but PTAA is hydrophobic and highly repellent to liquid perovskite ink. Subbiah said they were able to overcome the repellence by adding a surfactant to the ink formulation, resulting in ‘better quality interface and films, and better device performance’.

The researchers also explained that they switched the ink to a lower-boiling solvent, reducing ink drying time without the need for further processing steps.

Overall, they claim that their optimised slot-coated PSCs captured solar energy with up to 21.8 per cent efficiency - ‘a significant improvement’ on the 18.3 per cent previously recorded for PSCs made this way.

“The development of scalable deposition techniques for perovskite solar cells is essential to bring this technology from the research labs to the market,” De Wolf explained. “Our next steps are making large-area devices and modules using our developed technology and testing their stability in the lab and the outdoors, while continuing to improve performance.”

The team's findings have been published in ACS Energy Letters.