Perovskite cells in the future of photovoltaics
A team of researchers at the Polytechnic University of Turin, École Polytechnique Fédérale de Lausanne (EPFL),Polytechnic University of Milan and the Centre for Nanoscience and Technology of the Italian Institute of Technology (CNST-IIT) has conducted an experimental study on perovskite, a hybrid material, both organic and inorganic, able to absorb the entire solar spectrum and to transport the electric charge with high efficiency.
The study, published in Science, the journal of the American Association for the Advancement of Science, entitled “Improving efficiency and stability of perovskite solar cells with photocurable fluoropolymers”, is focused on perovskite solar cells and could be an important first step in improving next-generation photovoltaics, still little studied in Italy.
Perovskite has recently been studied by Professor Michael Grätzel (EPFL) for its possible applications in solar energy conversion devices. The promising results of the research allow us to assume large-scale application of this material by 2020.
Photovoltaic cells based on this technology, in addition to exploiting the unique properties of perovskite, can be produced by a simple and fast technology, with a sure industrial scalability. These characteristics have led universities and research centres worldwide to invest human and financial resources in the development of perovskite solar cells, with a dramatic increase in the sunlight conversion efficiencies of this technology, more than quintupled in the last six years.
The new technology has, however, a number of limitations to be overcome before moving to the industrial phase: perovskite solar cells have considerable losses in efficiency when exposed to ultraviolet light and atmospheric moisture and deteriorate in a very short time, at best after a few days.
The study published by Science addresses this crucial issue, by devising and proposing a coating made of an innovative polymeric material (fluorinated with micrometric thickness) that acts as a barrier against moisture and ensures self-cleaning characteristics to the solar panels, able to effectively counteract the ageing of perovskite solar cells.
Produced through photopolymerization, an extremely fast technique, economical and with low environmental impact, the polymeric coating was enhanced with luminescent molecules able to convert the ultraviolet light present in solar radiation in non-harmful light for the solar cell. The test results showed efficiencies close to 19% and exceptional stability, confirming the prospects of this new solar energy conversion technology.
At the Italian Institute of Technology, in addition to the research group of the CSF – IIT (Centre for Sustainable Futures) in Turin led by Guido Saracco, other laboratories are working in this field of research which the World Economic Forum has included among the 10 most promising technologies of 2016: the CNST-IIT team in Milan led by Annamaria Petrozza focuses, among other things, on improving the efficiency of perovskite solar panels, while the research team at the Graphene Labs, led by Francesco Bonaccorso, studies the integration of graphene and other two-dimensional materials in these new solar cells.
The word perovskite was coined by Gustav Rose in 1840 in honour of Lev Perovskiy, Minister of the Russian Imperial Court, a great collector of minerals. Perovskites are cubic-shaped opaque crystals with a particular crystal structure which can host a wide range of elements and has a variety of physical properties, including that of being an excellent conductor.