Study On Hydrothermal Synthesis Of WO₃ Nanostructures And Their Photoelectricity Properties

WO3 is an indirect band gap(2.4-2.8 e V) semiconductor material which can absorb visible light within the solar spectrum. It is a kind of promising material for excellent photocatalytic properties and gas sensitive properties. Thus, in the paper, the tungsten oxide films with different microstructures were synthesized and their photoelectric properties were discussed. In this article, in order to keep the morphology of the materials, we improved the structure of the device. WO3 films were fabricated on fluorine-doped tin oxide(FTO) substrates ablated by using a focused laser beam using a hydrothermal method. Then, through the surface modification and heat treatment process, the microstructures of WO3 films were adjusted. The main topics are summarized as follows.Firstly, we studied the influences of additives on the morphology of WO3 films. In this work, we use the NaWO4·2 H2 O as the raw material and the K2SO4,(NH4)2C2O4 as the additives. As a result, WO3 nanoplates were obtained under the help of(NH4)2C2O4. The average length and thickness of the platelets are ~500 nm and ~100 nm. While when the additive was K2SO4, the WO3 nanorods were obtained. The average length, width and thickness are ~800 nm, 100 nm and 50 nm, respectively.Secondly, we investigated the photoelectric properties of tungsten trioxide films with different heat treatment processes. The untreated-WO3 showed 2.5 times higher photocurrent value than hydrogen-treated WO3 and the hydrogen-treated WO3 shows 17 times higher photocurrent value than air-treated WO3. The experiments confirmed that both of the oxygen vacancies and phase structures had great influences on the photoelectric responses of WO3 films, and the influence of phase structure on the photoelectric performance of WO3 was far greater than that of oxygen vacancy. Furthermore, we find that H-WO3 showed high photosensitivity to infrared light in our study. The results confirmed that the solar energy can be achieved effective utilization by regulating the internal structures of materials.Finally, on the basis of heat treatment in the previous chapter, the parameter Pt was introduced. The quantitative results showed that the gas-sensitized WO3 film in formaldehyde exhibited much higher photocurrent than that in air. In addition, the sensitivity of Pt loaded hydrogenated WO3 to formaldehyde reached 15.8 which was nearly 15 times higher than that of the others. Moreover, Pt- loaded hydrogenated WO3 showed excellent electrical response towards formaldehyde in the dark. The intriguing performance of the Pt- loaded hydrogenated WO3 film indicated an efficient coupled effect of oxygen vacancies and Pt. The results provide the potential for improving the efficiency of photoelectric sensing devices by coupling two modification mechanisms.