Thermal decomposition kinetics of FAPbI3 thin films

In the realm of organic-inorganic-hybrid metal-halide perovskites, ${\mathrm{FAPbI}}_{3}$ is seeing increasing attention as a potentially more stable alternative to ${\mathrm{MAPbI}}_{3}$. To add to our previous paper, where we studied the reaction kinetics of the thermal decomposition of ${\mathrm{MAPbI}}_{3}$, here we analyze the compositional change and crystal phase evolution during the thermal decomposition of ${\mathrm{FAPbI}}_{3}$ thin films. To this end, we prepare the perovskite using thermal coevaporation and monitor the growth and thermal decomposition in vacuum with an in situ x-ray diffraction setup. The experimental procedure has been carried out via three approaches: producing a partially decomposed sample with the help of a graded temperature profile, using a temperature ramp and a set of isothermal decomposition experiments. From this data we analyze and calculate the stoichiometry and phase changes, the activation energy $E$ and the frequency factor $A$ of the thermal decomposition process, in addition to the thermal expansion coefficient during heating. We compare our results to the ones obtained for ${\mathrm{MAPbI}}_{3}$ thin films by the same experimental method, confirming the enhanced thermal stability of ${\mathrm{FAPbI}}_{3}$.