Hydration Intermediate Phase Regulated In‐Plane and Out‐Plane Epitaxy Growth of Oriented Nano‐Array Structures on Perovskite Single Crystals

Abstract Fabrication of organic–metal‐halide perovskite micro‐nano array structures draws attention to the potential application in polarized light, high‐resolution X‑ray imaging, light‐emitting diodes, and lasers. However, it is still challenging to achieve the growth of controllable long‐range ordered nanostructure arrays by chemical solution‐based techniques. Herein, controllable epitaxial growth of long‐range ordered micro‐nano arrays on MAPbI₃ single crystal (SC) surface is reported. A hydrated intermediate phase is found that can effectively regulate in‐plane and out‐plane orientated growth, respectively. This is attributed to the regulation of growth thermodynamics by hydration 0D perovskite intermediate phase enabling free recombination of PbI₄^2– octahedral cages. Further, it is found that the degree of hydration is the key to the realization of in‐plane and out‐plane growth. Meanwhile, polarization emission and amplified spontaneous emission property are observed in highly oriented nanorod arrays with potential applications in anti‐counterfeiting polarized emission.