Fabrication Of TiO₂ Nano-materials Based On Solar Cells

Titanium dioxide (TiO₂), being a wide-bandgap semiconductor materials with plentiful stock, non-toxic property and chemical stability, has seen enormous applications in such fields as photocatalysis, sensing and photovoltaic devices. Ever since the year of 1991 when M.Gratzel put forward the innovative concept of dye-sensitized solar cells (DSSCs) and thus opened up a new frontier for this material's application in solar cells, solar cells based on TiO₂ has been widely used. Titania has been used in various solar cell systems, from the DSSCs,the hybrid solar cells, to the inorganic semiconductor-sensitized solar cells, even to the quantum dot solar cells. Titania was the most important part of these solar cell systems and the role this material plays allowed by it's unique property is self-evident. Therefore the preparation of TiO₂ in it's right form which meet the demand of solar cell usage is the first step toward solar cells with higher photoelectric conversion efficiency and better stability.Since the nanocrystalline TiO₂ films was used in DSSCs, the nanocrystalline electrode based on various structures of TiO₂ (nanowires,nanorods,nanotube) has been proposed in succession. Among the various structures proposed, the most typical is the porous nanocrystalline titania thin film. The aim of this paper is to fabricate porous nanocrystalline titania thin film for solar cell use and further discuss the possibility of utilizing gold nanoparticles as sensitizer in the solar cell thus fabricated.The crystallographic, morphology and microstructural of the nanocrystalline TiO₂ films affect the photoelectric conversion efficiency of the solar cells deeply, for which, the first task of paper is the study of the preparation of TiO₂ nanoparticles. The sol-hydrothermal synthesis is used in the experiment, through the control of the precursor solutions, the hydrothermal temperature and time, we successfully regulate the crystallographic, size and morphology of the nanoparticles prepared, and ultrafine anatase TiO₂ nanoparticles is achieved. At present, the applications of one-dimensional TiO₂ nanostructures in the solar cells has attracted much attention, in light of which, we have tried to prepare TiO₂ nanowires and nanobelts in the experiments. While grope out the situations of fabricate anatase TiO₂ nanoparticles, two different methods has been used to prepare nanocrystalline TiO₂ films: the first is to use polyethylene glycols(PEG) as template, acting as structure-directing agent in the formation of nanocrystalline TiO₂ films, with further spinning coating on the ITO glass ,and in the end calcinate to form porous nanocrystalline films and meantime to get rid of the PEG template; the second is to use TiO₂ nanoparticles as binder of titanium alkoxide, with hydrothermal treatment to form pore nanocrystalline TiO₂ films.The bandgap of anatase TiO₂ is 3.2eV, thus the corresponding threshold wavelength of absorption is 387.5 nm, which hinders the application of TiO₂. For this reason, the expanding of absorption spectrum is critical in order to get high photoelectric conversion efficiency. At present, the road to expand the absorption spectrum includes doped semiconductor, dye-sensitizing, organic polymer sensitizing, inorganic semiconductor- sensitizing, quantum dot- sensitizing and so on, but all these methods to some extent have limitations. Recently, based on the wide application of surface plasmon resonance in metal nanostructure, the idea of metal nanostructure used as sensitizer was put forward. Based on it, this paper fabricate the Au/TiO₂ composite film to study the influence of surface plasmon resonance on absorption. In the experiment, we treat the deposition time of gold as altering variable and then measure the UV-vis spectrum of the composite films. From the spectrum, it can be seen the resonance absorption peak, indicating the potential to use gold nanoparticles as sensitizers in the solar cells.