Oriented Attachment of Perovskite Cesium Lead Bromide Nanocrystals

All-inorganic cesium lead halide (CsPbX3; X=Cl, Br, I) perovskite nanocrystals (NCs) have been appeared as a promising material for various opto-electronic applications. These perovskite NCs show high absorption co-efficient, high photoluminescence quantum yield (upto 90%), narrow photoluminescence full width half maxima, color tunable over entire visible range (400-700 nm) and more stable compared to bulk counterparts. The photo-physical properties of these NCs strongly depend on the interaction between the outermost atoms and corresponding surface bound organic passivating ligands. Some capping ligands are loosely connected to the perovskite NCs surface and can separate out very easily in presence of polar solvents. Our experimental observations reveal that in present of polar solvents CsPbBr3 NCs agglomerate among themselves via oriented attachment process and create big crystals by an Ostwald ripening process. While highly concentrated spherical CsPbBr3 NCs purified with excess acetonitrile, most of the NCs tends to attach and fuse together in (110) crystal plane to form micrometer sized nanorods. As far as I know, this is the first report on formation of micrometer sized 1-D CsPbBr3 nanorods from spherical NCs via oriented attachment process at room temperature.