Copper(I) Induced Phase Transition and 1D Growth in Cesium Lead Bromide Cubic Nanocrystals

Lead halide perovskites have been explored ardently in the past decade owing to their excellent photophysical properties. High-temperature cation exchange reactions have been employed to improve the stability and performance in perovskite lattice, but lacks control over size, shape, and stoichiometry. Herein, the solution phase interaction of cesium lead bromide (CsPbBr₃) nanocrystals with monovalent and bivalent copper ions, under ambient conditions is systematically investigated. The introduction of Cu¹⁺ explicitly initiates a one-dimensional growth with a distinct phase transition, that is from cubic to orthorhombic, while Cu²⁺ induces a partial exchange with Pb²⁺ with no phase change. DFT calculations suggest that Cu¹⁺ induces structural distortion via Cs¹⁺ substitution, altering the Goldschmidt tolerance factor and perovskite octahedral tilting, leading to the phase transition. Additionally, the oleic acid/amine ligands used to stabilize the nanocrystals, are preferentially etched away to form complexes with Cu¹⁺, initializing an oriented growth of the nanocubes to nanorods. A mechanistic investigation of the evolution of the nanorods gave insights on tuning the tolerance factor via room temperature modifications and cation exchanges in perovskites for anisotropy and morphology tuning. This effortlessly obtained perovskite nanorods with Cu¹⁺ could find effective applications in optoelectronics, and as novel photocatalysts.