Preparation And Properties Of WO₃-based Electrochromic Composites

The electrochromic(EC)smart window is a new type of smart window with strong appeal and great environmental benefits.It only needs very little electricity to control the brightness of the glass without obstructing the visibility like blinds.At the same time,it can control the sunlight transmittance,monitor the indoor temperature and lighting,and reduce the operating cost of air conditioners,fans and other electrical appliances.This electrochromic device can be used in conjunction with a smart home system,controlled by sensors,and has very high convenience and safety.The most important part of this device is the EC layer.Although tungsten trioxide(WO₃)has become the most widely studied inorganic EC layer material due to its high color rendering efficiency and fast coloring,it has a small light modulation range and recirculation.Disadvantages such as poor stability.Therefore,this paper selects a simple sol-gel method as the film forming method,and modifies WO₃ through structural design and doping methods to increase its light modulation range,shorten the response time,and improve its electrochromic performance to meet the actual requirements.demand.The specific research content is as follows:(1)First,the WO₃ film was synthesized by the sol-gel method,and structure-directing agents of different molecular weights were added to modify its structure.The structure and performance of WO₃ film were tested by X-ray diffraction analysis(XRD),scanning electron microscope(SEM),electrochemical workstation and ultraviolet-visible spectroscopy.The results show that compared with pure WO₃ film,WO₃ film with structure directing agent has significantly improved electrochromic performance.Among them,the WO₃ film with polyethylene glycol 600(PEG600)has the best performance,and the light modulation range is increased to 82.7%;the coloring time and fading time are 3.6 s and 4.0 s,respectively.(2)Secondly,a series of WO₃/SiO₂ composite films were prepared by using WO₃film added with PEG600 and silica in different proportions.The structure and performance of the composite film are tested by scanning electron microscopy,X-ray diffraction analysis,electrochemical testing,ultraviolet spectroscopy and other testing methods.The results show that the WO₃/SiO₂ composite film has better transparency and film-forming properties,and when the SiO₂ doping amount is 20%,the electrochromic performance of the composite film is the best,and its light modulation range reaches 88.7%.The coloring time is 2.4 s,and the fading time is 4.1 s.(3)Finally,the WO₃/TiO₂ composite film was prepared using Pluronic-F127 as a porogen and tetrabutyl titanate as a titanium source.The structure and performance of the composite film were tested by SEM,XRD,electrochemical testing,and ultraviolet spectroscopy.test.The results show that with the increase of TiO₂content,the light modulation range of the composite film increases,and the response time is shortened.When the TiO₂ doping amount is 15%,the composite film light modulation range is the largest,reaching 68.9%,and the response time is shortened.The time is 1.62 s,and the fade time is 0.80 s.However,the transparency of the composite film also decreases.