On the Stability of CsxFA(1-x)PbI3 Layers Obtained by a Single Step Spin Coating Process

It was possible to improve the chemical stability of FAPbI3 perovskite thin films (without altering other important characteristics such as the band gap or morphology) by introducing small amounts of Cesium atoms, when the films are deposited by a single step spin coating deposition process. It is shown that an optimum x = 0.33, for the prepared Cs
x
FA
(1-x)
PbI
3
thin films, provides a long degradation time (more than one month) as compared to pure FAPbI
3
in the alpha phase, which lasts for only one hour, under ambient conditions, before transforming to the degraded (non-desirable) delta phase. The bandgap variation for Cs
x
FA
(1-x)
PbI
3
as a function of x was also evaluated, and it was confirmed that this compound behaves approximately according to Vegard´s law.