Researchers at the University of Sheffield have found that storing perovskite precursor solutions at low temperatures extends their operational lifetime from under a month to over four months.

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 optimized.

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, the 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 PhD 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.”