4D-STEM in an FIB-SEM: A Proper Tool to Characterize Perovskite Single-Photon Emitters and Solar Cells

Four-dimensional scanning transmission electron microscopy (4D-STEM) is a characterization technique that allows high-resolution imaging of thin samples while providing structural and crystallographic information. We have developed a 4D-STEM solution for scanning electron microscopes, enabling lamella fabrication and analysis without exposing the lamella to air. This technique has been used to analyze emerging materials, including low-dimensional lead halide perovskites and perovskite solar cells. We resolved individual CsPbBr3 nanocrystals, determined their lattice constant, and mapped their crystallographic orientation, locating well-ordered superlattice ensembles for single-photon emission. In perovskite solar cells, we observed a nondegenerate tetragonal MAPbI3 photoactive layer and documented the amorphization and subsequent degradation of the MA3Bi2I9 photoactive layer when exposed to air. Our findings facilitate the identification and characterization of lead halide perovskite nanocrystal ensembles and perovskite photoactive layers, thereby reducing the time required for these processes. This efficiency is generally valuable for large-scale production and quality control of materials manufactured on an industrial scale.