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Graphene for the solar cells of the future

In Advanced Energy Materials a study led by the University of Florence

Overcoming silicon technology for a new economically viable and sustainable system is the challenge of photovoltaic research. A team led by the Department of Physics and Astronomy explained for the first time the positive effects of the use of graphene applied to a semiconductor class, the perovskites, to be the next alternative to silicon.

Using graphene could improve the performance of the solar cells of the future and make it economically more convenient. This is the result of a recent research published in the journal "Advanced Energy Materials", a result of the work of a team led by Anna Vinattieri, a professor of experimental physics, and by researcher Francesco Biccari, both at the Department of Physics and Astronomy at the University of Florence ("Graphene-Based Electron Transport Layers in Perovskite Solar Cells: A Step-Up for an Efficient Carrier Collection", DOI: 10.1002 / aenm.201701349).

"At present, the dominant technology in the field of photovoltaics is silicon-based, explains Anna Vinattieri. But in recent years, several studies have shown that a class of semiconductor minerals that share the same crystalline structure, the perovskites, lead to efficiencies in converting solar light into electricity (the so-called photovoltaic conversion) comparable to those of crystalline silicon technology. Perovskites, as much as silicon, are eco-friendly, continues Vinattieri, but as opposed to the latter, they are produced with a much simpler and cheaper processes which even allow them to be deposited on flexible substrates."
The UNIFI team, in collaboration with Aldo di Carlo (University of Rome Tor Vergata and The Center for Hybrid and Organic Solar Energy-CHOSE), Francesco Bonaccorso (Istituto Italiano di Tecnologia in Genoa) and Emmanuel Kymakis (Technological Educational Institute of Crete) has shown that, if appropriate quantities of graphene (G) and graphene oxide, "doped" with lithium atoms (GO-Li) are added within the solar cell of perovskite, both the speed in charge separation in the cell and the perovskite defect density are greatly improved, resulting in an increase in conversion efficiency.

"Other research has already used graphene oxide on perovskite cells," says Francesco Biccari, "but we were the first with optical measurements to investigate the positive effects of this use. The result is important not only for the increased efficiency achieved but also because the same technique can be experimented on other materials. Until now all experiments, including ours, have been carried out on perovskites consisting of an organic-inorganic hybrid compound, the organic part of which unfortunately degrades very rapidly in the presence of moisture. The scenario for the near future is the use of graphene and graphene oxide on completely inorganic perovskite cells: this will allow further advancements and such novel technologies will make their commercialisation closer. "

The research was funded by the Cassa di Risparmio di Firenze Foundation, the Ministry of Education, University and Research, and the European Framework Program for Research and Innovation Horizon 2020.

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25 October 2017