  Hybrid organometal halide perovskites (HP) present exceptional optoelectronic
properties, but their poor long-term stability is a major bottleneck for their
commercialization. Herein, we present a solvent-free approach to growing
single-crystal organic nanowires (ONW), nanoporous metal oxide scaffolds, and
HP to form a core@multishell architecture. The synthetic procedure is carried
out under mild vacuum conditions employing thermal evaporation for the
metal-free phthalocyanine (H2Pc) nanowires, which will be the core,
plasma-enhanced chemical vapor deposition (PECVD) for the TiO2 shell, and
co-evaporation of lead iodide (PbI2) and methylammonium iodide (CH3NH3I / MAI)
for the CH3NH3PbI3 (MAPbI3 / MAPI) perovskite shell. We present a detailed
characterization of the nanostructures by (S)-TEM and XRD, revealing a
different crystallization of the hybrid perovskite depending on the template:
while the growth on H2Pc nanowires induces the typical tetragonal structure of
the MAPI perovskite, a low-dimensional phase (LDP) was observed on the
one-dimensional TiO2 nanotubes. Such a combination yields an unprecedentedly
stable photoluminescence emission over 20 hours and over 300 hours after
encapsulation in polymethyl methacrylate (PMMA) under different atmospheres
including N2, air, and high moisture levels. In addition, the unique
one-dimensional morphology of the system, together with the high refractive
index HP, allows for a strong waveguiding effect along the nanowire length.
