High-efficiency hybrid halide perovskites: a complex material with a simple start in the crystallization process

units, surrounded by solvent molecules, is extended to HPs with inorganic A-cations. Here, in the case of fully inorganic systems, the core can be surrounded by alkali cations as well. Applying the extended core-shell model, it is shown that fully inorganic compositions favour corner-sharing octahedra within the core, whereas in precursor solutions of the mixed-cation (organic-inorganic)-mixed-halide HPs, the single-octahedron core arrangement is favoured. This indicates that the halide composition exerts a stronger influence than the A-site cation on the atomic arrangement of species in the HP precursor solution. Analysis of the SAXS form factor further reveals higher polydispersity in fully inorganic systems due to the greater variety of species in solution, while the mixed-cation composition exhibits reduced polydispersity, highlighting the impact of precursor chemistry on crystallisation pathways and, ultimately, device performance.