A series of tests carried out by the researchers, from the University of Sheffield’s Energy Institute and Department of Physics and Astronomy, have revealed that storing perovskite precursor solutions at low temperatures increases their shelf life extensively.
Understanding how to make perovskite solutions more durable and reliable could potentially make the manufacture of perovskite solar cells more efficient, as the process would require fewer batches of more stable material to be produced, saving time, reducing material waste and also allowing device yield and efficiency to be optimised.
Perovskite solar cells are a relatively new class of photovoltaic device that efficiently convert sunlight into electrical power, with devices being fabricated using simple solution-based techniques similar to those used in the printing industry. A number of companies are now looking to commercialise perovskite solar cells and are thinking about the best ways that they can be manufactured at high volume.
Precursor solutions are used to create the perovskite light-absorbing layer which is positioned between electrically conductive layers that are used to extract current from the device. The efficiency of a perovskite solar cell critically depends on the composition of the perovskite which is itself dependent on the chemistry of the precursor solution.
“If a company cannot produce large volumes of precursor solutions and be able to rely on them performing consistently, it further complicates the manufacturing process” said Professor David Lidzey, from the University of Sheffield’s Department of Physics and Astronomy. “We have shown that this problem can be side-stepped by storing such materials at low temperature. Understanding how these solutions change over time is of significant importance if we are to use them to make the highest performance solar cell devices.”
In collaboration with University of Sheffield spinout company, Ossila Ltd, the Physics and Astronomy researchers carried out a series of experiments to test the stability of perovskite precursors.
To explore ways to try and enhance the shelf-life of the perovskite precursor, the Sheffield researchers kept some of the precursor samples at room temperature and refrigerated others at four degrees celsius for varying periods of time. These aged solutions were then used to make solar cell devices. Other experiments looked at the structure and composition of the perovskite films created using aged solutions.
The findings, published in ChemSusChem, demonstrated that low temperatures are key to prolonging solution lifespan from much less than a month to over four months. This work addresses one part of a complex supply chain that will be needed for perovskite solar cell manufacture, and should help simplify the scale-up of this new class of photovoltaic device.
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