Extended Data Fig. 2: Morphological characterization during in situ core/shell particle synthesis process.
From: Ultra-bright, efficient and stable perovskite light-emitting diodes
a, SEM image of a perovskite thin film (after 1s of reaction time with BPA-THF solution) showing small grains cracked out from large 3D grain. b, STEM image of 50 nm-size perovskite crystal during in situ core/shell synthesis process. Yellow arrows indicate the defective perovskite surfaces that can be bound with BPA. c, HR-TEM image of another perovskite crystal showing ultra-small nanocrystals segregated during in situ core/shell synthesis process. Insets: Magnified HR-TEM images of ultra-small nanocrystals taken from the white-boxed regions labelled C1 and C2. d, e, High-resolution HAADF-STEM images of single perovskite nanograins with decreasing grain size. Magnified HAADF-STEM images of the grain surfaces (D1, D2, E1, E2, F1, F2, G1, G2) demonstrate that the BPA shell coverages on the grain surfaces gradually increase and the defective surface regions decrease as the grain size decreases.
