Preparation And Characterization Of SnO₂:F Films Coated On The Glass Substrates With TiO₂-SiO₂ Composite Film By Spray Pyrolysis Method

F-doped SnO2 (FTO) thin film is emerging as one of the best potential alternatives to other TCOs in TFT-LCD, thin film solar cells, not only due to its comparable electro-optical properties with ITO thin films, but also its costefectiveness (with inexpensive, abundant raw materials), and environment-friendly nature. FTO thin films has been researched and studied a lot. This article creatively utilized TiO2-SiO2 composite layer to prevent Na+ diffusing to FTO film, and decreasing interference color of the FTO films.Tetraethyl orthosilicate, tetrabutyl and ethanol were used for prepared TiO2-SiO2 composite sol precursors. Inorganic metal salts SnCl2·2H2O, mono-butyl tin trichloride(MBTC) and ammonium fluoride (NH4F) as precursors were used for preparing fluorine doped SnO2 (FTO) films on glass substrates. TiO2-SiO2 composite films were prepared on glass substrates by dip coating of sol-gel. FTO films were prepared on glass substrate, SiO2/glass and TiO2-SiO2/glass by spray pyrolysis. The transmission is detected by Uv-Vis and the optical constants are deduced from the fringe pattern of the transmission. The surface topography of the films is analyzed by SEM. The influence of the content of TiO2 and the process of anneal to the optical constants is studied. The sheet resistance was investigated by the means of four probe method. The crystal structure of the FTO films coated on TiO2-SiO2/glass substrates was analyzed by X-ray diffraction (XRD). The obtained results are as follow:(1) It has been shown that stability of sol is critical in production of the films. With the content of TiO2 in composite sol, the refractive index of composite films increased. When the content of TiO2 is 50%. the refractive index of composite films was 1.74, which could match to the the refractive index of FTO.(2) It was found that the stacks have a higher optical transmittance (up to 75% in the visible light region). With the Fluorine dopant amount increasing, the sheet resistance decreases gradually. When the Fluorine dopant amount is 5%, the heet resistance 8Ω/sq.(3) The films were found to be of cassiterite type with a tetragonal rutile structure. All the films contain the characteristic SnO2 peaks only. All films presented prominent (200) planes.(4) FTO films coated on 50%TiO2-50%SiO2 composite films could reduces reflecting interference color of the FTO films and prevent the Na ion diffusing.