The perovskite film data used in this work for clustering analysis is originally published in with full descriptions of the sample preparation and measurement processes. A condensed description is provided here in parts that are relevant for the clustering analysis. The perovskite thin films analyzed in this work were spin-coated on cleaned and UV-ozone-treated glass substrates. Over-stoichiometric PbI2 was used for synthesizing all the films in a molar ratio of 1.09 (PbI2) to 1 (CsI, MAI, and FAI). Lead(II) iodide solution was prepared in 9:1 N.Ndimethylformamide to dimethyl sulfoxide solvent. The precursor solutions were mixed to their nominal Cs-FA-MA compositions, chlorobenzene antisolvent was used in the spin-coating, and the spin-coated films were annealed at 403 K for 20 min before cooling them down to room temperature, cutting them in halves, and transporting the other half to XRD measurements and the other half to the degradation test. Grazing incidence X-ray diffraction with incidence angle of 1° was performed with Rigaku Smartlab with Cu-Kalpha sources. Reference XRD spectra obtained from literature for delta-CsPbI3 , delta-FAPbI3 , and alpha-perovskite were used as the basis of the XRD analysis of the cluster centroids. It should be noted that the thin film samples have lattice strain leading to peak shifts in the spectra compared to the reference powder samples.