Study On The Preparation And Optical Performance Of Transition Metal Oxide Electrochromic Films

Electrochromic technology is an intelligent color changing technology with low energy consumption.At present,it has been widely used in intelligent Windows of buildings,rearview mirrors of automobiles,Windows of aircraft and other equipment.The working principle of this high-tech technology is that the optical properties of thin film materials are dynamically changed by electric drive.However,the color variation of electrochromic materials is not rich enough,the technology has not been widely used in display technology,visible light camouflage,the color-changing back of the phone and other broader market areas.Vanadium pentoxide（V₂O₅）is an electrochromic material with rich color transformation,which can switch between yellow,green and gray colors.However,V₂O₅ can not be widely used as the working electrode of electrochromic equipment due to its poor cyclic color reversibility,low optical contrast modulation ability and low coloring efficiency.In order to obtain a V₂O₅ film with better electrochemical performance,this paper designed a V₂O₅/Ag composite film to solve the above problems,which significantly improved the electrochromic performance of V₂O₅ material.In order to further extend the chromic cycle life of V₂O₅ films,WO₃/V₂O₅ composite films were prepared on a coral-like nanostructured film of tungsten oxide（WO₃）obtained by hydrothermal method.The films have a long cycle life and good optical contrast modulation ability.Finally,life.The optical contrast modulation capability.Finally,using the V₂O₅/Ag composite film obtained in Chapter 2 as the electrochromic layer,the blank ITO conductive glass and the Prussian blue（PB）film were combined to assemble two multicolor electrochromic devices,the actual discoloration effect of the V₂O₅ based composite material assembled into a multicolor electrochromic device was tested,the influence of the choice of ion storage layer on its practical application is explored.The specific research content is as follows:（1）In order to optimize the electrochemical performance of the V₂O₅ film to improve its electrochromic ability,the nanoporous V₂O₅/Ag composite electrochromic film was successfully prepared by photochemical deposition of Ag nanoparticles on the electrodeposited V₂O₅ film.The V₂O₅/Ag composite film has a color efficiency of 55.4cm² c^-1,a fast color switching speed（coloring/bleaching time is 5 s/6 s）,a wider transmittance modulation range（51%,650 nm）and better cycle stability（no significant degradation after 100 cycles）compared to a single V₂O₅ film.The results show that the main reason for the improvement of electrochromic performance of the composite film is the nanoporous structure.This structure increases the surface area of the film,shortens the diffusion path of metal cation and facilitates the oxidation-reduction reaction.（2）To get the longer cycle life electrochromic film,WO₃ film was prepared on FTO-coated glass by hydrothermal method,WO₃/V₂O₅ was obtained by electrodeposition of V₂O₅ on WO₃ thin films,the composite film contains two kinds of electrochromic materials,this composite film has nano porous structure which is conducive to the efficient transport of metal ions.The WO₃/V₂O₅ composite film have a coloration efficiency of 44.7 cm² c^-1,a coloration/bleaching switching speed of 6 s/8 s,and demonstrate a wider transmittance modulation range（42%,650 nm）and a longer cycle life（no significant degradation after 300 cycles）compared to a single V₂O₅ film.The results show that the WO₃ coral-like nanostructure as the substrate is the main reason for the improvement of electrochromic performance of the composite film,which can improve the structural stability of the film,so that the structure of the film is not destroyed after the metal cations are inserted and extracted multiple times.（3）In order to explore the color change effect of the V₂O₅/Ag electrochromic film assembled into a multicolor electrochromic device and the influence of the choice of ion storage layer on its performance,the V₂O₅/Ag film was used as the electrochromic layer,the blank ITO and the PB film prepared by electrodeposition method is used as the counter electrode（ion storage layer）,and the electrochromic device is assembled using a certain ratio of lithium perchlorate,propylene carbonate,and polymethyl methacrylate as the electrolyte.The（V₂O₅/Ag）/PB electrochromic device using PB film as the ion storage layer achieves a color change similar to that of a single V₂O₅/Ag film（from blue-black to green to yellow）,compared to（V₂O₅/Ag）/ITO devices have longer cycle life（maintain good performance after 50 cycles）and wider transmittance modulation range（40%,650 nm）,This indicates that the PB film as the ion storage layer of the V₂O₅/Ag based electrochromic device is beneficial to its electrochromic performance.,and it also shows that the multicolor electrochromic device based on the V₂O₅/Ag film has practical value.