Researchers find solution to reduce waste in solar cell production

Scientists have discovered a more efficient way of storing the chemical compounds used in perovskite solar cells that could help make the manufacturing process more efficient and create less waste.

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.

Professor David Lidzey, from the University of Sheffield's Department of Physics and Astronomy, said, "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. We have shown that this problem can be side-stepped by storing such materials at low temperature."

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.

"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," added Professor Lidzey.

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.

Lead Ph.D. Researcher, Mary O'Kane from the Department of Physics and Astronomy at the University of Sheffield, said, "While searching for a simple method to increase precursor-solution shelf-life, we also had to use a series of techniques to understand how the chemical composition of the solution changed with time. This allowed us to identify several key reactions that caused their degradation."

Their 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.

The University of Sheffield's Department of Physics and Astronomy explores the fundamental laws of the universe and develops pioneering technologies with real-world applications. Our researchers are looking beyond our planet to map out distant galaxies, tackling global challenges including energy security, and exploring the opportunities presented by quantum computing and 2D materials.

More information:
Mary E. O'Kane et al, Perovskites on Ice: An Additive‐Free Approach to Increase the Shelf‐Life of Triple‐Cation Perovskite Precursor Solutions, ChemSusChem (2021). DOI: 10.1002/cssc.202100332

Provided by University of Sheffield