Light and water are well known factors that can cause degradation to organic lead halide perovskites, which hinders their commercial applications. Here, we studied the degradation mechanism of FA0.85Cs0.15PbI3 using peak force infrared microscopy, which enables subdiffractional spatial identification of the formamidinium (FA) cation and allows us to probe the degradation mechanism of individual grains. We found that upon exposure to light or water alone, no significant change in the spatial distribution of FA and no pure inorganic decomposition product was observed. However, upon exposure to both light and high humidity, we found that FA0.85Cs0.15PbI3 degrades through a multistep pathway. First, α-FA0.85Cs0.15PbI3 decays to δo-CsPbI3, δ-FAPbI3, and PbI2 and the distribution of the FA cation became increasingly inhomogeneous. Second, the organic cations are lost and PbI2 further photodecomposes.

Nanoscale degradation mechanism of mixed cation perovskite under humidity and light revealed by peak force infrared microscopy

Macromolecular Chemistry: The Second Century

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ACS Spring 2020 National Meeting & Expo

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.