化学溶液沉积法制备WO_3·2H_2O薄膜及其电致变色性能

Preparation of WO_3·2H_2O Thin Films by Chemical Solution Deposition and Electrochromic Properties

目的研究具有不同微观结构的WO_3·2H_2O薄膜的电致变色性能。方法采用化学溶液沉积法在FTO玻璃上制备WO_3·2H_2O薄膜,通过加入不同的形貌控制剂(柠檬酸或草酸铵),制备不同纳米结构的WO_3·2H_2O薄膜。采用X射线衍射仪(XRD)和扫描电子显微镜(SEM)分析薄膜的成分结构和微观形貌,利用紫外可见光分光光度计对薄膜在波长为200～1000nm范围内的透光性进行研究,并通过电化学工作站对薄膜进行电化学性能分析。结果采用柠檬酸作为形貌控制剂制备的WO_3·2H_2O薄膜的透光性高达82%左右,其在着色和褪色状态的透过率差值为36.2%。通过添加柠檬酸或草酸铵作为形貌控制剂制备的WO_3·2H_2O薄膜均呈现出纳米片状结构,纳米片的厚度分别为5～15 nm和50～60 nm,但是采用柠檬酸制备的WO_3·2H_2O具有较多的间隙和裂缝,使其表现出了较好的电致变色性能。结论具有间隙和裂缝的纳米WO_3·2H_2O薄膜增加了薄膜与电解质的接触面积,减少了离子扩散的路径距离,更小的纳米结构可以提供更多的化学活性位点,从而表现出较好的电致变色性能。

The work aims to study electrochromic properties of tungsten oxide dihydrate films with different microstructures. Tungsten oxide dihydrate films were prepared on FTO by chemical solution deposition method. Different nanostructured WO3·2H2O films were synthesized by adding different morphology control agents(citric acid or ammonium oxalate). The composition and microstructure of the films were analyzed by X-ray diffraction(XRD) and scanning electron microscopy(SEM).UV-visible spectrophotometer was used to study the transmittance of films with wave length within 200~1000 nm and electrochromic performance of the films was investigated by an electrochemical workstation. The transmittance of WO3·2H2O film prepared with citric acid as the morphology control agent reached 82%, and the transmittance difference of film in colored and faded state was 36.2%. The WO3·2H2O films prepared by adding citric acid or ammonium oxalate as the morphology control agent exhibited nano-sheet structure. The thickness of the nanosheets was 5~15 nm and 50~60 nm, respectively. However,WO3·2H2O prepared with citric acid had more gaps and cracks, which exhibited better electrochromic properties. WO3·2H2O film with gaps and cracks increases the contact area between the film and the electrolyte, and reduces the path distance of ion diffusion. The smaller nanostructures can provide more chemically active sites, thus showing better electrochromic properties.