Solvent Vapor Annealing of CsPbI3 Nanocrystal Superlattices Followed by In Situ X-ray Scattering

Tetragonal superlattices of orientationally ordered, cube-shaped, perovskite CsPbI₃ nanocrystals were annealed with hexane vapor and characterized with in situ grazing incidence small- and wide-angle X-ray scattering (GISAXS/GIWAXS). The superlattice expands in all directions and periodic order is retained in the c-direction orthogonal to the substrate, while in-plane orientational order is eventually lost. The tetragonal superlattice structure with orientational nanocrystal order is recovered after removing the solvent vapor. The perovskite crystal structure of the CsPbI₃ nanocrystals remains unaffected throughout the solvent vapor annealing process.