Morphology-Controlled Vapor-Phase Nanowire Growth with Ruddlesden–Popper Lead Bromide Perovskite
Pushpender Yadav, Kyeongdeuk Moon, Anupam Biswas, Christopher K. Herrera, Yunlu Zhang, Scott Calabrese Barton, Richard R. Lunt, G. J. Blanchard, Seokhyoung Kim
Abstract
Two-dimensional (2D) Ruddlesden–Popper (RP) halide perovskite has attracted significant attention as a promising candidate for high-efficiency light sources. RP perovskites, when synthesized into well-defined nanowires (NWs), have the potential to serve as nanoscale coherent light sources by incorporating optical cavity effects with their light emission behaviors. However, RP perovskites tend to grow in macroscopic thin sheets as opposed to relevant NW structures due to the layered nature of the crystal lattice, which necessitates a new way of controlling nanoscale morphologies. Here, we achieve NWs of RP BA 2 PbBr 4 (BA = butylammonium), for the first time, using chemical vapor deposition (CVD) by systematically navigating a wide range of growth conditions and constructing growth regimes of distinct morphologies. Of the two particular regimes that produce well-formed nanostructures, we find that RP BA 2 PbBr 4 grows into energetically favored thin nanoplatelets (NPLs) at high temperatures, whereas intermediate temperatures allow it to first grow into three-dimensional (3D) pyramidal nuclei and then get elongated into NWs upon continued growth. We propose temperature-dependent diffusion of surface species as a deciding factor of our morphological control. We present crystallographic and elemental analyses to confirm that our NWs have the appropriate lattice structures and chemical stoichiometry of BA 2 PbBr 4 . Static and time-resolved optical measurements show quantized absorption and emission features at 400 and 406 nm, respectively, with a radiative decay time of 1.7 ns that is much quicker than the 8.7 ns decay time of a prototypical 3D CsPbBr 3 perovskite. The RP NWs exhibit a strong exciton binding energy of 279 meV, which can be understood by the reduced dimensionality of BA 2 PbBr 4 . The strong absorption and radiative emission characteristics suggest that the RP BA 2 PbBr 4 NWs are good candidates as bright, ultrasmall light sources for nanophotonic and optical communication applications.