A simple method of synthesizing nanomaterials and the ability to control the size and position of them are crucial for fabricating nanodevices. In this work, we developed a novel ammonia aqueous solution method for growing well-aligned ZnO nanorod arrays on a silicon substrate. For ZnO nanorod growth, a thin zinc metal seed layer was deposited on a silicon substrate by thermal evaporation. Uniform ZnO nanorods were grown on the zinc-coated silicon substrate in aqueous solution containing zinc nitrate and ammonia water. The growth temperature was as low as 60-90 degrees C and a 4-in. wafer size scale up was possible. The morphology of a zinc metal seed layer, pH, growth temperature, and concentration of zinc salt in aqueous solution were important parameters to determine growth characteristics such as average diameters and lengths of ZnO nanorods. We could demonstrate the discrete controlled growth of ZnO nanorods using sequential, tailored growth steps. By combining our novel solution method and general photolithography, we selectively grew ZnO nanorod arrays on a patterned silicon substrate. Our concepts on controlled ZnO nanorod growth using a simple solution method would be applicable for various nanodevice fabrications.

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In this study, a novel and facile passivation process for a perovskite solar cell is reported. Poor stability in ambient atmosphere, which is the most critical demerit of a perovskite solar cell, is overcome by a simple passivation process using a hydrophobic polymer layer. Teflon, the hydrophobic polymer, is deposited on the top of a perovskite solar cell by a spin-coating method. With the hydrophobic passivation, the perovskite solar cell shows negligible degradation after a 30 day storage in ambient atmosphere. Suppressed degradation of the perovskite film is proved in various ways: X-ray diffraction, light absorption spectrum, and quartz crystal microbalance. This simple but effective passivation process suggests new kind of approach to enhance stability of perovskite solar cells to moisture.

In this communication, a novel CdSe/CdS/ZnO nanowire array fabricated by a 3-step solution-based method was used as a photoanode of a quantum dot sensitized solar cell, which generated a maximum power conversion efficiency of 4.15%.

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Tungsten oxide (WO 3 ) nanowires were prepared on a tungsten (W) substrate by thermal evaporation of WO 3 powder at elevated temperature in a tube furnace. The morphology, structure, composition, and chemical state of the prepared nanowires were characterized by SEM, EDX, TEM, XRD, Raman spectroscopic, and XPS measurements. The nanowires grown using WO 3 powder were found to have uniform morphology with a high density and a crystalline structure consistent with monoclinic WO 3 . The field-emission measurements showed that the prepared nanowires have a turn-on field of 4.8 V/µm. The role of WO 3 powder in the growth of high-density nanowires has been discussed by comparing the above results with those of nanowires grown without using WO 3 powder and also on a different substrate. Also, the effects of growth temperature on the chemical binding states and product morphology of the nanowires were investigated.

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Supporting information I: SEM images of CuO/ZnO heterostructured nanorod Figure S1 shows the growth steps of CuO nano-spikes on surface of ZnO nanorods by photochemical method. CuO nanospikes were grown not only on tips of ZnO nanorods but also on body surface of ZnO nanorods. The formation of CuO nucleation was observed at low Cu slat concentration of 0.025 mM under short time (~ 2 mins) irradiation of UV by SEM analysis. The surface coverage level of fully grown CuO nanospikes on surface of ZnO nanorods becomes larger as Cu salt concentration increases (0.025~ 0.1mM). After formation of high surface coverage, the CuO is formed like a porous CuO layer and the thickness of CuO layer increases on ZnO.