Synthesis Of TiO₂ Nano-array For Photovoltaic Devices

Titanium dioxide is a wide-bandgap semiconductor material with unique photocatalytic properties and optical properties. The band gaps of rutile, anatase and brookite are 3.2eV,3.2eV and 2.96eV, respectively. Research on TiO₂ has become one of the hot-spots in the field of energy and environment. Ordered one-dimensional or two-dimensional TiO₂ nano array structures, which possess direct electronic transmission channels, can reduce the occurrence of charge recombination during the charge transfer process. It will be far-reaching significance to improve its photoelectric properties. This article focuses on the synthesis of four kinds of ordered TiO₂ nano array structure and regulation of morphology. In addition, the structures are applied for dye-sensitized solar cell and constructing a three-dimensional amorphous silicon solar cells. The main work of this article is as follows.A variety of novel TiO₂ nanostructure arrays was synthesized by hydrothermal or anodization methods. Their formation mechanisms were discussed based on the relation between the reaction parameters and the morphology of the TiO₂ structures. With tetrabutyl titanate （TBOT） and hydrochloric acid （HCl） as the reactants in the hydrothermal process, different structural TiO₂ nanowire array on fluorine doped tin oxide （FTO） glass were fabricated by modifying the reactant contents, the seed layer and the orientation of the substrates. TiO₂ nanosheet array on FTO substrate was obtained by hydrothermal method with TBOT/acetic acid （HOAc）/AgNO3 as the reactants, and its structure was modified by the reactant contents and the thermal annealing parameters. Moreover, TiO₂ nanotube array on titanium foil and FTO substrates were also fabricated through anodization method with NH4F/ethylene glycol/H2O as the electrolyte. By adjusting the parameters in the anodization process, TiO₂ interpenetrating porous film with titanium film was obtained.The TiO₂ films are applied in dye-sensitized solar cells （DSSCs） as photoanodes, which enable the DSSCs performing excellent photovoltaic performance. A novel photoanode with TiO₂ nanosheet array and a TiO₂ scattering layer was fabricated, leading to a remarkable improvement in the device performance of the DSSCs. The efficiency of the DSSC with this novel photoanode is 17% higher than that of the DSSC with standard nanoparticular （P25） photoanode. TiO₂ nanostructure array was also applied as the framework to construct three-dimensional （3D） amorphous silicon thin film solar cells. The optical absorption of amorphous silicon with 3D framework is 25%～100% higher than that with the planar structure. The photovoltaic performance of the 3D amorphous silicon solar cells was also investigated.