Limiting Halide Exchange and Doping Mn(II) in Vertex-Oriented Cube-Connected Patterned Lead Halide Perovskite Nanorods

Abstract

Lead halide perovskite nanocrystals remained in the forefront of inorganic optical nanomaterials for a decade. The chemistry of their formation leading to bright and phase-stable nanocrystals is also largely understood. However, this study mostly focuses on isotropic nanostructures and is limited to anisotropic shapes. Again, the study of shape anisotropy is more explored for orthorhombic CsPbBr₃ and limited for the high-bandgap cubic phase CsPbCl₃ nanocrystals. Keeping this in mind, herein, the halide exchange is carried out in a specific cube-connected patterned vertex-oriented nanorod of CsPbBr₃ intending for complete conversion to CsPbCl₃. The host CsPbBr₃ nanorods are prepared here by B-site cation exchange in CsCdBr₃ following a Cs-sublattice platform, as no such traditional protocol has been developed for their direct synthesis. In addition, direct synthesis of CdCdCl₃ nanorods having an appropriate Cs-sublattice framework leading to anisotropic CsPbCl₃ nanorods is also not achieved in a similar pathway. Hence, cubic CsPbCl₃ nanorods are targeted from CsPbBr₃ through anion exchange. However, it is observed that such anion exchange has a limiting stage beyond which the anisotropic rod is dismantled into isotropic cube structures. The chemistry of control of such limiting parameters is investigated, and the phase–shape relationship during the anion exchange is established. The key observation here for such a unique shape of CsPbBr₃ is related to their orthorhombic phase, which lost its sublattice structure when the phase slowly converted to a pure cubic phase. However, with optimum Cl insertion, the mixed halide perovskite nanorods are retained, and these are also further doped with Mn(II) for obtaining anisotropic doped nanorods, and their changes in optical features are reported. Hence, the shape–phase relationship in anisotropic halide perovskite nanorods matters and controls the limit of halide exchange leading to the mixed halide perovskite anisotropic nanorods.