Hi Habibur

Sorry for the delay in replying. Depending on the crystallinity of your (solar cell) materials, you will get more or less well-defined powder rings or oriented blobs in the GIWAXS on your 2D detector at specific locations based on the ordering within and between the organic molecules. Your question really comes down to what you mean by “the phase purity of your out of plane crystallites”. If, by phase purity, you mean different structural phases then you can look at the shape and distribution of the GIWAXS pattern. To determine a phase of the material, you need to compare relative intensities of different Bragg reflections. So, several rings or 2theta intensities will be needed and this might mean working at high photon energies and/or at close sample-to-detector distance. This (for one phase) is already difficult. To distinguish between two (or different) phases, you have to identify the Bragg peaks associated with each and compare their relative intensities and shapes. The presence of multiple phases may manifest through asymmetry in peak shapes or peaks in unexpected locations. On the other hand, if by phase purity you are referring to stoichiometry it is much more difficult as you really need to look at the relative peak intensities which are more prone to experimental artefacts.

An alternative may be differential scanning calorimetry (DSC). The technique looks at how materials behave at phase transitions (normally associated with heating the sample). Pure systems will have a sharp phase transition, but these would be broadened if there were multiple stoichiometries or phases I expect. I am not an expert, but it might be worth looking into. An alternative would also be some sort of spectroscopy such as IR or even Brillouin Light scattering. I am an expert in neither, but you might be able to seek others who are.

Thanks again,

Tom

Kind Regards,
Habibur
PhD Student
UNSW