Fig. 2: Crystal facet-dependent ion migration of MAPbBr3 perovskite films.
a X-ray diffraction (XRD) pattern of perovskite films with pure solvent and different ratios of 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (BMITFSI) additives. Grazing-incidence wide-angle X-ray scattering (GIWAXS) patterns of perovskite films (b), with additive, and (c) without additive. d Diffraction peak intensity of (110) crystal facets of perovskite films with additive and without additive. The schematic diagram of the (e), (100) crystal facet, and the (f), (110) crystal facet. Scanning electron microscopy (SEM) morphology and the corresponding schematic of perovskite films fabricated (g), with additive and (h), without BMITFSI additive. Photoluminescence photographs of mix-halide perovskite films. i, with additive, and (j), without BMITFSI additive under different ultraviolet (UV) irradiation times. The bromide ion migration paths in the (k), (100) crystal facets and the (l), (110) crystal facets. The red dashed circles represent the ___location of migrating ion. m, n The calculated ion migration activation energies for the (100) crystal facets and the (110) crystal facets.
