1. Perovskite solar cells like to work at the edge


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    This illustration shows a side view of sheets of perovskite. The coloured pattern represents perovskite and the grey lines symbolize the water-repelling surfaces.

    A team of researchers from Lund University in Sweden and Fudan University in China have successfully designed a new structural organization using the promising solar cell material perovskite. They have found that the efficiency of a perovskite solar cell increases when it self-organizes to stand on edge.

    Perovskite is a new and highly promising material in the context of solar cells. In its regular form, however, the material is very sensitive to moisture; it simply dissolves in contact with water, and even normal humidity deteriorates the material within hours or minutes. As the researchers report in a paper in Advanced Energy Materials, they have now found a way to 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 10%," says Tönu Pullerits, professor of chemical physics at Lund University.

    Pullerits sees great development potential for solar cells based on perovskite, thanks to the outcome of the current study. The researchers not only built thin sheets of the material with water-repelling surfaces, but also discovered, to their surprise, that these perovskite sheets self-organized in a way that clearly increased their efficiency.

    Since the sheets are so thin, many need to be layered on top of each other to ensure they absorb sufficient sunlight. A problem arises at this point, however, because 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, reducing the efficiency of the solar cells.

    The researchers first tested two different water-repelling surfaces. They expected one version to give better results, allowing the electrons to jump more easily from one sheet to another. Instead, they found the opposite – the second version gave much better results. This surprised them and led them to undertake new experiments to understand the reason.

    "Here, our laser experiments were crucial. We could show that the sheets with the second surface material self-organized in such a way as to stand on edge instead of lying flat against one another," explains Pullerits.

    Thanks to this self-organizing behavior, the electrons were able to move freely between the sheets, considerably increasing the efficiency with which the sheets could convert solar energy into electricity. Pullerits sees this result as an important step on the way to constructing stable and efficient solar cells out of perovskite. "Stability is a key issue for solar cells," he says.

    This story is adapted from material from Lund University, with editorial changes made by Materials Today. The views expressed in this article do not necessarily represent those of Elsevier. Link to original source.

    Perovskite solar cells like to work at the edge
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