Controlled growth of dodecapod-branched CsPbBr3 nanocrystals and their application in white light emitting diodes

All-inorganic metal halide perovskite (e.g., CsPbX3, X = Cl, Br, I) nanocrystals show excellent shape-dependent photophysical properties which have motivated the active exploration of new synthetic approaches for higher morphological complexity than those produced by current methods (cubes, plates, rods). Here, for the first time, we demonstrate that the transformation of Cs4PbBr6 to CsPbBr3 coupled with an overgrowth scheme can be exploited to produce CsPbBr3 dodecapods, each of which is composed of 12 well-defined branches. The critical step is the formation of cuboctahedral Cs4PbBr6 seeds in a Cs-rich environment induced by the faster dissolution of CsOAc than PbBr2. A phase transformation from Cs4PbBr6 to CsPbBr3 then leads to the growth of twelve branches from the twelve vertices, producing CsPbBr3 dodecapods with a high photoluminescence quantum yield (50%) and a narrow full width at half maximum (18 nm). We further demonstrate the production of dodecapods of CsPbX3 (X = Cl, I) NCs with tunable emission covering the full visible region (415-685 nm) through an anion exchange process. Furthermore, white light emitting diodes (WLEDs) fabricated with CsPbBr3 nanoflowers demonstrated a 135% color gamut of the National Television System Committee (NTSC) standard. This work not only adds a distinct new morphology to the CsPbX3 nanocrystal family but also sheds light on the fundamental understanding of the growth mechanism of these newly emerged functional materials.