Epitaxially Connected CsPbBr<sub>3</sub>–PbTe Perovskite-Chalcogenide Nanocrystal Heterostructures
Rajdeep Das, Souvik Banerjee, Diptam Nasipuri, Narayan Pradhan
Abstract
Connecting two crystalline nanomaterials epitaxially requires minimal lattice mismatch and strong chemically interactive interface bonding. For binary materials having both cations and anions in the crystal lattice, surface ions at the junction facets play a crucial role in efficient bonding. Hence, establishing epitaxial heterostructures between ionic perovskite and covalent chalcogenide nanostructures has remained synthetically difficult and is also less explored in halide perovskite nanocrystals. In this study, by extending the Pb sublattice, perovskite-chalcogenide heterostructures of CsPbBr 3 –PbTe are reported. Minimizing the bromide concentration in the reaction medium and Pb-rich facets of CsPbBr 3 facilitated the formation of such heterostructures . By tuning the amine-to-acid ratio, the length of PbTe on the facet of CsPbBr 3 is regulated. Based on extensive electron microscopic imaging analysis, the epitaxial junctions are established between the (101) or (011) facets of orthorhombic CsPbBr 3 (space group Pbnm ) and the (111) facet of cubic PbTe. While absorption spectra remain unaltered, the emission is quenched in this heterostructure case. In spite of the larger Te anion size, the formation of such epitaxial heterostructures indeed suggests that other perovskite-chalcogenide nanocrystals might be possible with optimized reaction chemistry.