Chemical and Structural Stability of CsPbX Nanorods during Postsynthetic Anion-Exchange: Implications for Optoelectronic Functionality.

We examine halide anion-exchange reactions on CsPbX nanorods (NRs), and we identify reaction conditions that provide complete anion exchange while retaining both the highly quantum-confined 1-D morphology and metastable crystal lattice configurations that span a range between tetragonal structures and thermodynamically preferred orthorhombic structures. We find that the chemical stability of CsPbBr NRs is degraded by the presence of alkyl amines that etch CsPbBr and result in the formation of CsPbBr and 2-D bromoplumbates. Our study outlines strategies for maintaining metastable states of the soft lattices of perovskite nanocrystals undergoing exchange reactions, despite the thermodynamic driving force toward more stable lattice configurations during this disruptive chemical transformation. These strategies can be used to fine-tune the band gap of LHP-based nanostructures while preserving structure-property relationships that are contingent on metastable shapes and crystal configurations, aiding optoelectronic applications of these materials.