Researchers from Lund University in Sweden and Fudan University in China have designed a new structural organization using perovskites that could greatly benefit perovskite-based solar cells. Perovskites, in their regular form, are sensitive to moisture and dissolve in contact with water, and even normal humidity deteriorates the material. Now, the researchers claim to have overcome this problem.
"We have succeeded in producing thin sheets with a water-repelling surface, making the whole construction much more stable. In addition, we have succeeded in orienting the sheets so as to obtain acceptable solar cells, with an efficiency of ten percent," says professor of chemical physics at Lund University.
Since the sheets are so thin, many need to be layered on top of each other in order for the absorption of sunlight to be sufficient. A problem arises at this point in that the water-repelling surfaces do not allow electrons to circulate freely within the material. It becomes difficult for the electrons to jump from one sheet to another, which reduces efficiency in the solar cells.
The researchers first tested two different water-repelling surfaces. They expected one version to give better results, enabling the electrons to jump more easily from one sheet to another. Instead, the outcome was the opposite - the second version gave much better results. This surprised the researchers, who then started new experiments in order to understand why.
"Here, our laser experiments were crucial. We could show that the sheets with the second surface material self-organised in such a way as to stand on edge instead of lying flat against one another," say the researchers.
Thanks to the self-organizing structure of the sheets, the electrons were able to move freely between the contacts, considerably increasing the efficiency of converting the solar energy to electricity. The team sees the result as an important step on the way to constructing stable and efficient solar cells out of perovskite.