Mechanism of water degradation of methyl ammonium lead iodide (MAPI) perovskite.

What is it about?

We use a new surface analysis technique which allows us to measure the surface chemistry of materials under water vapour pressures of up to 9 mbar. This allows us to monitor the changes in chemistry of a methyl ammonium lead iodide thin film in real time.

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Why is it important?

We find a degradation pathway that involves production of hydrogen iodide and ammonia resulting in loss of the methyl ammonium ion. This allows chemists to design surface capping materials which can prevent the water/methylammonium ion reaction occurring and reduce the degradation rate.