Study On Structure Control And Electrochromic Performance Optimization Of Tungsten Oxide Thin Films

WO₃ is an important transition metal oxide semiconductor material.It has good electrochromic,photochromic and photocatalytic properties.It can be used in electrochromic smart windows,gas sensors,photocatalysts and other fields.In this paper,different preparation methods and experimental parameters were used to prepare WO₃ films with different structures.The film was characterized and analyzed by X-ray diffractometer,metallurgical microscope,field emission scanning electron microscope,ultraviolet-visible spectrophotometer and self-made electrical testing equipment.The effects of different annealing conditions on the structure,morphology,optical and electrical properties of tungsten oxide films were studied in depth,and the electrochromic properties of the prepared films were explored.The WO_3-x（0≤x<1）film was prepared by ion beam sputtering deposition and annealing treatment,and the effects of different annealing parameters on the crystal structure and photoelectric properties of the tungsten oxide film were studied.The study found that under a wet oxygen annealing atmosphere,the crystallinity of the tungsten oxide film will get better and better as the annealing time increases and the annealing temperature rises,the main crystalline phase of WO₃ is enhanced more obviously,and some oxygen-deficient phases will also appear one after another;Under dry oxygen conditions,with the increase of temperature and time during annealing,the resistance value of the tungsten oxide film gradually decreases,and the visible light transmittance is also significantly increased;in addition,the tungsten oxide film electrochromic device performs well The electrochromic characteristic,its optical modulation value can reach 70%at the wavelength of 632.8 nm.The porous nanocrystalline WO₃ film was prepared by the method of ion beam sputtering deposition film,combined with post-annealing and dealloying.The study found that the prepared WO₃ membrane has obvious porous structure on the surface and inside.The crystal grain size of the crystalline porous WO₃ film is in the range of 6 nm to 13 nm.The porous nanocrystalline WO₃ film has a higher resistance because it has more surface scattering than an amorphous film.In addition,the porous nanocrystalline WO₃ film has a unique temperature coefficient of resistance and excellent optical properties.Compared with the amorphous WO₃ film,the porous nanocrystalline WO₃ film has a higher light transmittance at the wavelength of visible light.At the same time,the band gap（2.75e V）of the porous nanocrystalline WO₃ film is also larger than the band gap（2.10～1.70e V）of the amorphous WO₃ film.