Promising step in perovskite solar cells: organic building blocks provide much greater stability

More stable perovskite

In 2009, the material perovskite was first used as a solar cell. At the time, it achieved an energy yield of barely 3.9 percent. A few years later, it was already close to 26 percent. This meant that the material achieved the same efficiency as the silicon solar cells that are now standard on our roofs. And yet perovskite solar cells are hundreds of times thinner than silicon solar cells and therefore much cheaper and more durable. "Perovskites are a very promising material for replacing silicon as a solar cell in the future. Only there is one big problem: perovskite solar cells are incredibly unstable. If you start with an efficiency of 26 percent, that efficiency drops to zero not much later. Comparable to an airplane that takes off and gradually crashes when it reaches its altitude," says Dr. Wouter Van Gompel.

Stable for 5 months now

Perovskites are salts, so on contact with moisture they absorb water and disintegrate on average after 1 to 3 days if we do not encapsulate the perovskite in a protective layer. For many years now, the Hybrid Materials Design research group of imo-imomec, the integrated research institute of Hasselt University and imec, has been working, within the EnergyVille collaboration, on ways of making perovskites more stable so that they can effectively be widely used as solar cells or in other applications such as LEDs, photodetectors or transistors. To do this, they are developing organic building blocks that they build into the structure. "By doing so, we create a so-called 2D-perovskite that can withstand both moisture and temperatures of up to 230 degrees. By adding our organic building blocks to the perovskite, we make the material more stable from the inside out. The best results in our lab show that even under 77 percent humidity, our material has been stable for 5 months (without additional protection), and continues to increase," says PhD researcher Paul-Henry Denis.

Future

Before perovskites can be widely used in a variety of applications, a lot of research is still needed. "Our strategy of adding organic building blocks is enormously versatile," says postdoctoral researcher Wouter Van Gompel "The properties of the organic building blocks we use can be further optimized by adapting their molecular structure based on what we have learned so far. We expect that in this way we can still make gains in terms of stability and efficiency". The knowledge within this research on the structure of materials is also one of the important pillars within the new master program Materiomics that will start in September 2022 at UHasselt.

"And in addition, there is still a lot of potential to make perovskite better," says PhD researcher Martijn Mertens. "Our organic building blocks improve the internal stability of the perovskite material. Now you can think of external ways to additionally improve the stability of perovskite solar cells. For example, by working with coatings and protective layers on the outside of the material that allow you to eliminate even more and very specific external stress factors. The future belongs to perovskite, we as a research group are convinced of that."

This research could count on financial support from FWO and BOF.