Substrate Functionalization to Improve the Stability of α-FAPbI₃

One of the major limitations of the commercialization of perovskite solar is the scalability of the different fabrication processes. In this context, thermal evaporation offers several advantages compared to solution processes, such as higher uniformity, better control of the thickness, deposition of non-soluble materials, and avoiding the removal of solvent orthogonality. Co-evaporation of FAPbI₃ is a promising choice for the fabrication of highly efficient and scalable perovskite solar cells. However, the presence of the non-perovskite hexagonal phase, which is the most stable phase at room temperature, is detrimental to the device's performance. Here, grazing incident wide-angle X-ray scattering (GIWAXS), X-ray diffraction (XRD), and X-ray fluorescence (XRF) techniques are used to understand the role that intermolecular forces (i.e. hydrogen bonds, dipole-dipole, van der Waals) between the perovskite and the substrate plays in determining the crystalline structure and crystallographic orientation of FAPbI₃ deposited by thermal evaporation