Solvent Vapor Annealing\nof CsPbI<sub>3</sub> Nanocrystal\nSuperlattices Followed by <i>In Situ</i> X‑ray Scattering

Tetragonal superlattices of orientationally ordered,\ncube-shaped,\nperovskite CsPbI<sub>3</sub> nanocrystals were annealed with hexane\nvapor and characterized with <i>in situ</i> grazing incidence\nsmall- and wide-angle X-ray scattering (GISAXS/GIWAXS). The superlattice\nexpands in all directions and periodic order is retained in the <i>c</i>-direction orthogonal to the substrate, while in-plane\norientational order is eventually lost. The tetragonal superlattice\nstructure with orientational nanocrystal order is recovered after\nremoving the solvent vapor. The perovskite crystal structure of the\nCsPbI<sub>3</sub> nanocrystals remains unaffected throughout the solvent\nvapor annealing process.