The de X-RAY diffraction method is one of the methods found to be widely used in various fields. It has proven the possibility of a detailed analysis of the materials. In the years of use, multiple data has been collected through this research method. The database allows comparison with other materials and phase composition.
As already indicated, XRD is not only a simple technique like others. Using diffraction you can investigate different properties of crystalline materials. You can identify phases by their lattice parameters, you can derive the phases fractions in mixtures, you can determine symmetry change by peak splitting, you can collect information about lattice strain in order to evaluate stress, you can investigate the alignment of million of crystals described by the texture of the material, you can derive the atomic arrangement (crystal structure), the chemical diffusion (bei lattice parameter variation), you also can use the peak profiles in order to determine the grain size distribution or even lattice defects. I am sure that I still forgot some very advanced techniques which are based on diffraction and enables a correlation with important properties of state-of-the-art materials.
However, the material you mentioned is certainly investigated also by other alternative techniques which deliver not integrated information but locally resolved characteristics.It surprises me that you do not found this elsewhere?
With synchrotron XRD you can monitor in-situ simultaneous photovoltaic and structural evolution of perovskite solar cells during film formation. Laboratory XRD is still too slow for that. You need a synchrotron source for that, although systems such as the XENOCS are getting closer to earlier synchrotrons.
Have a look at: https://pubs.rsc.org/en/content/articlehtml/2018/ee/c7ee03013d
The third generation synchrotron X-ray source at the European Synchrotron Research Facility (ESRF) in Grenoble, which make available X-ray beams of higher energy and much higher intensity than laboratory X-ray sources, can be used monitor in-situ simultaneous photovoltaic and structural evolution of perovskite solar cells during film formation.
Powder XRD (and this is what we are talking about) helps to check whether your microcrystalline (rather nanocrystalline) material is phase pure. You do not need a single crystal and you can check a large portion of your material with this method.
Needless to say, that you should not work with materials which are not phase pure.