Preparation Of TiO₂ Nanocrystalline Thin Film And Study On Its Photoelectric Properties

Nanocrystal TiO₂ thin film has advantages of simple preparation, low cost, good chemical stability and low toxicity. It is a widely applicable inorganic material. According to its characteristics of wide band gap, insensitive to visible light and sensitive to ultraviolet, we studied the ultraviolet response of TiO₂ thin film, looking forward to making an UV detector with low-cost, high-performance, and fast-response.Nanocrystalline TiO₂ was prepared by sol-gel method, and porous TiO₂ thin film electrode was prepared by sol-gel method on ITO conductive glass using dip-coating method. The crystal, structure, morphology and optical properties of the samples were studied by X-ray diffraction(XRD), infrared spectroscopy(IR),photoluminescence spectra(PL), atomic force microscope(AFM) and UV-visible spectroscopy(UV-vis). Using TiO₂ thin film as the working electrode, saturated calomel electrode as reference electrode, platinum wire as counter electrode, Na₂SO₄ as electrolyte, we made a photoelectrochemical cell UV detector, and the photoelectric properties of thin-film electrode was studied.The results showed that because there were many defects and dislocations in anatase phase TiO₂ lattice, there were many oxygen vacancies to capture the photoinduced electrons, the photoelectric activity of anatase phase was higher than that of rutile phase. In addition, the thickness of thin film had a significant influence on photocurrent. The thicker the film was, the more ultraviolet the film can absorb, the more electron-hole pairs there were, so the higher the photocurrent would be. However, when reached to a certain thickness, the probability of electron-hole recombination increased, so the photocurrent decreased with the increase of thickness. When the film electrode was irradiated with 310nm UV light, it had the highest photocurrent. With the increase of electrode potential, the photocurrent had an enhanced trend. When the potential reached 0.4V, the photocurrent trended to saturation and grew slowly. As soon as the light was on, the film responsed rapidly. The response time was less than 1 s and the photocurrent had no change in 100s. We had also found that the intensity of photocurrent was related to the electrolyte concentration and PH value. When the electrolyte concentration and PH value were higher, the photocurrent was higher too. The addition of PEG made the porous structure of film surface, increased the contact area between the electrolyte and the film, and created favorable condition for the transfer of carriers. It was benefit to enhance its photoelectric property.The TiO₂-Ga electrode was prepared by adding Ga³⁺ ion to TiO₂ thin film.The addition of Ga³⁺ ion reduced the grain size and impeded phase transition. The photoelectric property of TiO₂-Ga was lower than that of intrinsic film, and the higher the doping concentration was, the smaller the photocurrent was. It is probably that when Ga³⁺ is doped, the surface of TiO₂ film will generate many defects, which will become the recombination centers of electrons and holes, reducing photoelectric property of TiO₂ film..