Researchers at Northwestern University have found that large-scale perovskite films, commonly used in solar technology, can be protected by liquid crystals that can respond to temperature change to avoid accumulating precipitation.

The new protection method achieved a stabilized efficiency of 21% for solar modules with enhanced damp heat stability, that is, 85% relative humidity at 85 degrees Celsius and a size of 31 sq cm. The earlier recorded efficiency was 19.5% for the highest certified stabilized aperture-area efficiency for perovskite solar modules exceeding 30 sq cm.

While organic-inorganic hybrid perovskite solar cells have shown promise in producing solar energy, they have only achieved an energy-to-power conversion efficiency of 26% in small samples. Scaling up perovskite solar cells to produce power at a larger scale has been hindered due to defects that arise from how the solutions are processed.

To combat this, a team of chemistry and engineering researchers at Northwestern University developed a method to accelerate the widespread industry adoption of perovskite solar cells.

In a study published in the Nature Energy journal, the researchers said they had developed a new material processing method to achieve uniform protection from defects on large-scale perovskite films, which achieved a record stabilized efficiency. They aimed to incorporate liquid crystals that homogenized and minimized defects of large perovskite films, yielding enhanced device performance. While extensive work has been done in bolstering perovskites to replace silicon, the usage of liquid crystals might represent significant progress.

“The liquid crystal strategy helps address a critical issue in the scale-up of perovskite solar cells, which demonstrates the potential for more efficient and stable solar energy generation on a larger scale, making it more robust for real-world applications,” said Yi Yang, a postdoctoral fellow, part of the researching team. It highlights the necessity for developing tailored solutions to minimize performance gaps in the scale-up process, she adds.

Prior research on liquid crystals used them as common additives in perovskite films but overlooked their ability to change with temperatures. This allowed for the regulation of crystal growth and prevented defects in large-area perovskite films, presenting potential for applications in the future.

“This methodology can be extended to the slot-die coating process, facilitating the production of larger-area perovskite submodules,” Yang said. “Exploring the functionality and phase structure of liquid crystal molecules presents an opportunity to enhance passivation effects and bolster device stability.”

Several new methods have been developed to improve the commercial utility of perovskite cells and improve their adoption across solar technology.

Last March, researchers at UK-based Swansea University established a low-cost and scalable carbon ink formulation with the potential for large-scale manufacturing of perovskite solar cells.

Early this year, a research team created tandem cells by combining silicon-based semiconductors with perovskites to make the cells last longer.