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

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.