Cesium lead mixed-halide perovskite thin films were fabricated by using a chemical vapor anion exchange procedure. Optical and structural properties of the materials obtained were studied comprehensively.

Inorganic cesium lead halide perovskite nanowires, generating laser emission in the broad spectral range at room temperature and low threshold, have become powerful tools for the cutting-edge applications in the optoelectronics and nanophotonics. However, to achieve high-quality nanowires with the outstanding optical properties, it was necessary to employ long-lasting and costly methods of their synthesis, as well as postsynthetic separation and transfer procedures that are not convenient for large-scale production. Here we report a novel approach to fabricate high-quality CsPbBr3 nanolasers obtained by rapid precipitation from dimethyl sulfoxide solution sprayed onto hydrophobic substrates at ambient conditions. The synthesis technique allows producing the well-separated nanowires with a broad size distribution of 2–50 μm in 5–7 min, being the fastest method to the best of our knowledge. The formation of nanowires occurs via ligand-assisted reprecipitation triggered by intermolecular proton transfer from (CH3)2­CHOH to H2O in the presence of a minor amount of water. The XRD patterns confirm an orthorhombic crystal structure of the as-grown CsPbBr3 single nanowires. Scanning electron microscopy images reveal their regular shape and truncated pyramidal end facets, while high-resolution transmission electron microscopy ones demonstrate their single-crystal structure. The lifetime of excitonic emission of the nanowires is found to be 7 ns, when the samples are excited with energy below the lasing threshold, manifesting the low concentration of defect states. The measured nanolasers of different lengths exhibit pronounced stimulated emission above 13 μJ cm–2 excitation threshold with quality factor Q = 1017–6166. Their high performance is assumed to be related to their monocrystalline structure, low concentration of defect states, and improved end facet reflectivity.

Porous films without periodic structuration were formed by direct current anodizing the surface of type-304 stainless steel in glycerol solution containing NH4F and H2O at elevated temperatures. Formed in the solutions containing both NH4F and H2O at the constant voltage mode of up to 50 V, these films are thin (∼1.0–1.2 μm) and yellow, whereas those formed at higher voltages, ca. 60–70 V, are thicker (up to 15 μm) and greenish. Note that these porous films are composed of both amorphous and crystalline species. X-ray diffraction (XRD), energy-dispersive X-ray (EDX), and X-ray photoemission spectroscopy (XPS) investigations and the detailed chemical analysis of incorporated elements revealed the complex nature of these films varied depending on the anodizing solution composition and voltage value applied. On the basis of the obtained data, the possible mechanism of formation of the glycerol anodic films on the SS304 substrate is presented. Compositional and structural transitions of as-grown films to material composed of crystalline Cr1.3Fe0.7O3 and spinel-type species were achieved via calcination procedure of anodized samples in air at 700 °C.

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