Researchers find they can stop the degradation of promising solar cell materials

Georgia Tech materials engineers have discovered the mechanism that causes a promising new material for solar cells to degrade and were able to stop it with a thin layer of molecules that repel water.

Their findings are the first step in solving one of the main limitations of metal halide perovskites, which are already as efficient as the best silicon-based solar cells at capturing light and converting it into electricity. They reported their work in the Journal of the American Chemical Society.

“Perovskites have the potential to transform not only the way we produce solar energy, but also the way we make semiconductors for other types of applications like LEDs or phototransistors. We can think about it for applications in quantum information technologies, such as light emission for quantum communication.” said Juan-Pablo Correa-Baena, assistant professor in the School of Materials Science and Engineering and lead author of the study. “These materials have impressive and very promising properties.”

Perovskite development accelerated, particularly after engineers and chemists recognized their potential for more efficient solar cells a decade ago. The problem with metal halide perovskites is that they are unstable when they interact with water and oxygen, transforming into a different structure that doesn’t work well for creating solar energy.

The Georgia Tech team discovered why, using X-ray scattering and spectroscopy to study chemical interactions between perovskites and the environment. The researchers found that the complex interaction of water and oxygen with perovskites leads to instability; by removing one of those that preserved the energy-capturing crystal structure of the perovskites.

“Before this paper, people thought that if you only exposed them to water, these materials degraded. If you exposed them only to oxygen, these materials degraded. We decoupled one from the other,” said Correa-Baena, who is also a Goizueta. Early career professorship. “If you prevent either one from interacting with the perovskites, you mostly avoid degradation.”

Correa-Baena’s team, which included collaborators from Brookhaven and Argonne National Laboratories as well as Italy and Germany, tested their discovery by adding a thin layer of a material called phenethylammonium iodide (PEAI). on a perovskite film. PEAI molecules repel water, and the researchers found that this was enough to stabilize the structure of the perovskites and therefore their energy conversion efficiency.

However, PEAI has drawbacks. “These molecules are very good at preventing water from interacting with the perovskite, but they are also very poor in terms of thermal stability,” Correa-Baena said.

Once sunlight hits the perovskite cells and they heat up, the PEAI molecules begin to move and their effectiveness decreases. The team is now working on the problem of thermal stability.

For this, Correa-Baena turns to Georgia Tech chemist and materials scientist Antonio Facchetti to develop new molecules that can prevent interactions with water and remain stable at high temperatures.

It will be the next chapter in a story Correa-Baena said Tech is writing to help make Georgia a leader in emerging solar energy technology.

“There’s already a lot of interest in the industry, with companies in the United States popping up and trying to commercialize this product. All the technology we’re creating here at Georgia Tech will eventually be able to be translated into industry,” he said. declared. “We want to create an ecosystem in which Georgia becomes important in solar manufacturing activities, and we hope that this will include perovskites.”