Because they are so cheap to make, perovskite solar cells have been at the center of much recent solar research. As a consequence, their efficiency has risen from less than 4 percent in 2009 to over 24 percent at present, which is close to traditional silicon cells. So-called tandem cells, which combine silicon and perovskite cells, achieve an efficiency of more than 28 percent.



Despite this success, perovskite has a number of defects due to the nature of the material and the way it is manufactured. Over time, vacancies in the atomic structure of the metal halide trigger the degradation of the perovskite under the influence of moisture, light and heat.

Protective layer

The researchers in Eindhoven, Twente and Beijing have experimented with a new type of perovskite, by adding a small amount of fluoride in the production process. Just like fluoride in toothpaste, the fluoride ions form a protective layer around the crystal, preventing the diffusion of the harmful defects.

