Solar cells harness energy from the sun and provide an alternative to non-renewable energy sources like fossil fuels. However, they face challenges from costly manufacturing processes and poor efficiency - the amount of sunlight converted to useable energy.

Light-absorbing materials called hybrid halide perovskites are used in a new type of solar cells that have shown great promise, as they are more flexible and cheaper to manufacture than traditional solar cells made of silicon.

However, perovskite solar cells degrade rapidly in natural conditions, greatly decreasing their performance in a matter of days.

This breakdown is due to the formation of ‘superoxides’ that attack the perovskite material, which are formed when light hitting the cells releases electrons, which then react with oxygen in the air.

Now in a study published in Nature Communications Dr Christopher Eames and Professor Saiful Islam from the University of Bath, working with colleagues from Imperial College London, have determined how the superoxides form and how they attack the perovskite solar cell material, and have proposed possible solutions.

The team found that superoxide formation is helped by spaces or ‘vacancies’ in the structure of the perovskite normally taken up by atoms of iodide. These vacancies are found to be the location for the formation of superoxides.

The team found that dosing the material with extra iodide after manufacturing improved stability.

Lead author of the new study, Nicholas Aristidou, a PhD student in the research group of Dr Saif Haque from the Department of Chemistry at Imperial, said: “After identifying the role of iodide vacancies in generating superoxide, we could successfully improve the material stability by filling these vacancies with additional iodide ions.”

Professor Saiful Islam added: “The new fundamental insights from our study will help in the design of perovskite solar cells with much better long-term stability”.

'Fast oxygen diffusion and iodide defects mediate oxygen induced degradation of perovskite solar cells' by Nicholas Aristidou, Christopher Eames, Irene Sanchez-Molina, Xiangnan Bu, Jan Kosco, M. Saiful Islam and Saif A. Haque is published in Nature Communications.