Thanks to his double bachelor’s and master’s degrees, Pols has a background in both chemistry and physics – exactly the expertise needed for his research on materials for electronic applications, such as solar cells, LEDs, and photodetectors. “In our research group, we study what processes take place in the material, with the goal of improving it for different applications,” he explains. “Unlike some other groups, our work is exclusively based on simulations.”

The material he is concerned with is perovskite – a mineral that turns out to be particularly promising for use in solar cells. His work deals with a specific class of perovskites – halide perovskites – that have the potential to replace silicon and form the basis for a new generation of solar panels.

Unique, but unstable

“Perovskite is a mineral with unique properties,” he says. As halide perovskites absorb light very well, they’re particularly suitable for use in solar cells. Moreover, they are easier and cheaper to make than silicon solar cells, while offering almost the same efficiency. This makes them ideal for applications in which weight plays an important role, such as in solar panels for buildings or in vehicles.

But the material also has drawbacks, Pols admits. “The biggest disadvantage is that the material is very unstable and falls apart quickly,” he says. Current perovskites normally remain stable for no more than three months. “Imagine if I sell a solar panel like that to someone and it falls apart after three months. They won’t be happy, as you understand,” he says with a smile. “So one of the big challenges is: how do you get the material stable?”

Customize properties

Fortunately, the material is particularly modular, meaning that the chemical composition and crystal structure of perovskites can be modified relatively easily by adding or taking out different elements. “You can add atoms and achieve the desired structure, such as different layers on top of each other,” Pols explains. “That way you can tailor the properties of perovskites to specific applications.” In addition, it’s possible to create so-called chirality – an asymmetry in the chemical structure, which makes the material absorb light in a different way.

All these possibilities make perovskites extremely versatile. “In theory, we can solve the stability problem by modifying the structure,” Pols says. “But for that we first need to understand what happens exactly. Right now, we don’t really know why the material falls apart.”

Too much to keep track of

With his research, he seeks to provide more insight into these processes. And he’s certainly not the only one; perovskites are a particularly dynamic and active field of research. The cabinet in the hallway of the Cascade building, which houses his research group, is therefore full of dissertations with perovskites in the title. Researchers focus on a variety of aspects of the promising material. “Some concentrate on improving energy efficiency, while others do experimental research on material properties, such as the movement of atoms within the material,” he clarifies.

“An awful lot of papers are published on this subject every day, too many to keep track of. There are even entire conferences devoted to perovskites,” Pols says. The enormous flow of new knowledge is valuable, but sometimes you can’t see the forest for the trees, he admits. “As a researcher, you always have to make choices about what to delve into, and you can never get a complete overview of the entire field.”