Kinetics of Ion-Exchange Reactions in Hybrid Organic–Inorganic Perovskite Thin Films Studied by In Situ Real-Time X‑ray Scattering

The exchange of ions
in hybrid organic–inorganic perovskites
with the general formula APbX3 (A = MA, FA; X = I, Cl,
Br) is studied in five different systems using in situ real-time grazing
incident X-ray diffraction (GIXD). In systems where the organic cation
is exchanged, we find a continuous shift of the lattice parameter.
The relative shift compared to the pure materials is used to quantify
the exchange. Whether or not a conversion is possible, as well as
the amount of exchanged cations, depends on the halide used. In the
case of the interconversion of MAPbI3 and MAPbCl3, we observe a decay of the diffraction peaks of the original perovskite
and the emergence of new peaks corresponding to the structure with
the alternative halide. Moreover, we determined the relevant time
scales of the growth and decay of the perovskite structures.