| dc.description | The utilization of the ZnO in the nanotechnology is widely spread due to its
superior properties, such as wide direct bang gap (~3.37eV), high exciton binding
energy of 60 meV, non-toxicity and low cost [1]. The hexagonal crystalline
structure allows obtaining a larger diversity morphologies and this allows its
utilization in: UV lasers, piezoelectric crystal, chemical sensor, gas sensor, light
emitting diode, photo detectors, and solar cells. One such morphology of ZnO thin
film is the one-dimensional (1D) sub-micron rods or nanorods and nanowires,
which has attracted interest due to a larger surface area and high aspect ratio. In
the solar cell the ZnO has been utilized in the electrode for the dye-sensitized cell
in substitution of TiO2. In this study, ZnO nanostructured thin films were prepared
by successive ionic layer adsorption and reaction (SILAR) on SnO2-coated glass
substrates [2]. In this procedure, the substrate is immersed in successive aqueous
baths containing zinc nitrate hydrate and/or hexamethylenetetramine, hydrogen
peroxide and triethanolamine. The pH solution was adjusted by addiction of
ammonium hydroxide. At a low zinc nitrate concentration of 0.01M the surface is
formed by individual nucleus. At a concentration of 0.02 M nanorod arrays were
shown and this morphology is of special interest for solar cells application, but
the deposition time used in this experiment was insufficient to promote the
desired thickness. At a higher concentration of 0.03 M rice like branches
morphology was observed but nanorods formation in the flowers was also present.
The angular petals suggest that the growth was taken on polar face. For DSSCs
applications the thin films prepared in 0.02 M solution was found to be the best
choice. | |
