Perovskite solar cells: UK innovation can help scale up production

Researchers at the SPECIFIC Innovation and Knowledge Centre at Swansea University in the U.K. have developed the world's first perovskite full printable perovskite photovoltaic solar cells. Made using a slot die coating in a roll-to-roll process, the method will enable the production of solar cells at a low cost, enabling their adoption.

Perovskite-based solar technologies are the next generation of solar cells that have demonstrated the potential for high energy conversion efficiency and lower production costs. Large-scale production of perovskites has been attempted using printing or coating techniques. However, roll-to-roll production has not been achieved before.

All hands on deck approach

To get to the bottom of the issues preventing such production, the Center brought together a team of chemists, materials scientists, and engineers all on-site.

One of the major hurdles the team came across was the gold electrode that was applied to the perovskite solar cell. Not only is this an expensive component of the entire assembly, but it also uses a slow evaporation process after the device is printed, preventing the production from being scaled up.

The researchers were looking for a suitable alternative to the gold electrode and, by using X-ray diffraction analysis, found that carbon electrode ink was the right solvent to achieve drying of the film without dissolving the underlying layer.

"This innovative layer can be applied continuously and compatibly with the underlying layers at a low temperature and high speed," said David Beynon, Senior Research Officer at SPECIFIC, who was involved in the research.

Further analysis of the carbon electrode-equipped solar cells showed that photovoltaic performance on a rigid glass substrate was similar to that of the evaporated gold electrodes with power conversion efficiencies of 13-14 percent and demonstrating long-term stability as well.

The researchers then used the roll-to-roll production method to print 65 feet (20 m) long flexible substrate, demonstrating an energy conversion efficiency of 10.8 percent.

"In just four years, this innovative method for PV has been designed and made, assessed and analyzed in detail, adapted and improved, making the possibility of printing and installing millions of meters of solar cells across the globe closer than ever," added Ershad Parvazian, Postdoctoral Researcher at the University in a press release.

The researchers now want to build something with printed solar cells that resemble a solar panel and then install it on buildings to demonstrate to people how well it works.

The research findings were published in the journal Advanced Materials.

Abstract

Perovskite photovoltaics have shown great promise in device efficiency but also the promise of scalability through solution-processed manufacture. Efforts to scale perovskites have been taken through printable mesoporous scaffolds and slot die coating of flexible substrates roll-to-roll (R2R). However, to date, there has been no demonstration of entirely R2R-coated devices due to the lack of a compatible solution-processable back electrode; instead, high-value evaporated metal contacts are employed as a post process. Here, in this study, the combination of a low-temperature device structure and R2R-compatible solution formulations is employed to make a fully R2R printable device architecture overcoming interlayer incompatibilities and recombination losses. Therefore, the n–i–p device structure of SnO2/perovskite/poly(3,4-ethylenedioxythiophene)/carbon is employed to form an ohmic contact between a p-type semiconductor and printable carbon electrode. In particular, the results show that the small-scale device efficiencies of 13–14% are achieved, matching the device performance of evaporated gold electrodes. Also, this entirely R2R-coated perovskite prototype represents a game changer, reaching over 10% (10.8) stabilized power conversion efficiency with unencapsulated long-term stability retaining 84% of its original efficiency over 1000 h under 70% RH and 25 °C.