Extended Data Fig. 3: SEM / EDS imaging of (BA)2PbBr4-(BA)2(MA)2Pb3I10 vertical heterostructure.
From: Layer-by-layer anionic diffusion in two-dimensional halide perovskite vertical heterostructures
SEM images of (BA)2PbBr4xI4(1-x) alloy formed after placing bulk crystal of (BA)2(MA)2Pb3I10 on top of (BA)2PbBr4 nanocrystal and heating it for a, 4 hrs and e, 10 hrs at 80 °C. EDS elemental mappings of b, f, Pb, c, g, Br, and d, h, I for the SEM images in a and e, respectively. All scale bars are 3 µm. i, j, EDS spectrum corresponding to the SEM images in a and e, respectively. The insets show the zoomed-in spectrum to highlight the bromine and iodine counts. The weak iodine signal in EDS elemental mapping and spectrum after 4 hrs of heating suggest that the iodine ions diffused to only top few layers of the bromide perovskite after 4 hrs of heating. After 10 hrs of heating, almost all the bromide perovskite layers show dominant iodine composition as evident from the EDS mapping and spectrum.
