The Hydrothermal Synthesis Of TiO₂Nanordos Array And Its Photoelectric Property

The photo-anode in DSSC is of vital importance for the cell’s PCE, for it not only acts as the carrier for dye molecular, but also provides the path for electron transportation. Since1D nanostructure can provide direct transport pathways for charge carriers, the electron transport along the long axis of the crystalline nanowires is expected to be several orders of magnitude faster than that in the random network of nanoparticles.It is well known that immobilizing nanotubes or nanorods onto solid substrates isessential for many applications.In this regard, this paper deals with direct hydrothermal growth of1D TiO2nanostructures onto a solid substrate. The work can be divided into two parts; one is based on the rutile titania nanorods array and the other is centered on the preparation of anatase titania nanorods array grown directly onto the fluorine-doped transparent conductive oxide glass (FTO).As to the preparation of one-dimensional rutile titaniananorods array via hydrothermal synthesis, the novelty of this work is the introduction of seed layer in the FTO before hydrothermal synthesis. During the synthesis of rutile nanorods array, the existence of seed layer improved the uniformity and the rod density of the array film, so did the performance of the DSSCs fabricated with the rutile array. Besides, the oriented growth direction changed from [101] to [001] after coating the seed layer on growth substrate.What is more, seed layer is the key factor of growing anatase nanorod directly onto the FTO substrate which compensates the lattice dismatch between SnO2in FTO and anatase. Experimental parameters were explored to obtain desired nanostructure and to unveil the growth mechanism. A new growth mechanism"seed decomposition recrystallization-oriented growth" was proposed. The anatase nanorods arraywith thickness of2.3μm wasfabricated into DSSC, and the PCE was2.1%, higher than the DSSCs fabricated with anatase nanoparticles film of the same thickness. And this has confirmed that nanorod arrays could facilitate the electron transportation in photo-anode, and equip the DSSCs with improved performances.In the last chapter, the nanoparticles with different morphologies were tested for photovoltaic performances. And the PCE results illustrated that the bowknot-like titania performed the best for it possessed the highest specific surface area. Besides, it was found that one black hydrothermal product was N-doped TiO2/C nanocomposite, which can absorb in the whole visible light region. Photocatalytic degradation measurements of methylene blue under visible light have confirmed that this black N-TiO2/C have photocatalytic activity under visible light.