Design Electrochromic Devices Based On Transparent Electrode Of Metal Nanowires

Electrochromism refers to a phenomenon in which when a certain voltage or current is applied to a color-changing material,a reversible color change occurs in the color-changing material.Devices fabricated by electrochromism are called electrochromic devices.With the development of science and technology,the demand for electrochromic devices in society is also increasing.Electrochromic devices are widely used in displays,automotive anti-glare mirrors,and smart windows in buildings.Large area applications of electrochromic devices can reduce energy consumption and make life more convenient.The research of electrochromic devices is mainly reflected in the improvement of device response time and prolongation of cycle life.In this paper,we focus on the improvement of the electrochromic device conductive layer and the structure of the electrochromic device design,to explore the best ratio of silver nanowires prepared by hydrothermal method.In the prior electrochromic device preparation,the conductive layer is mainly indium tin oxide（ITO）,but the indium tin oxide has a strong ceramic property,lacks flexibility,and the preparation conditions are harsh and need to be prepared in a vacuum environment.The resources are scarce and the cost is expensive.On the other hand,silver nanowires have excellent electrical conductivity,excellent flex resistance,and excellent performances of high transmittance and low haze.In the experiment,we fabricated a flexible electrochromic device based on a metallic silver nanowire transparent conductive film.First,a relatively long mature silver hydrothermal method was used to synthesize silver nanowires with high aspect ratio,using roller coating and dipping.A silver nanowire/graphene composite film was prepared by coating to replace indium tin oxide（ITO）as a transparent conductive layer.The specific steps are as follows:First,a plurality of layers of silver nanowires are roll coated on polyethylene（PET）using a roller coating method to obtain a transparent conductive film having conductive properties.In order to improve the bridging degree between the silver nanowires and tightly connect the silver nanowires,a mechanical imprinting method is used to mechanically imprint the conductive film coated with the silver nanowires so that the silver nanowires are more closely attached to the PET liner.At the bottom,the degree of bridging between the silver nanowires was strengthened,and a silver nanowire conductive film having excellent performance was obtained.Subsequently,the graphene and the ethanol are ultrasonically shaken,and a certain concentration of the graphene solution is used,and the silver nanowire transparent conductive film is immersed in the graphene solution by a dip coating method so that the graphene is coated on the surface of the silver nanowire and the graphite is used.The corrosion resistance of the olefin improves the weather resistance of the transparent electrode of the electrochromic device,increases the cycle life of the electrochromic device,and thus improves the stability of the electrochromic device.Subsequently,the silver nanowire/graphene conductive material is coated.The film is placed in an oven for drying to improve the conductivity of the film.The prepared silver nanowire/graphene transparent conductive film is placed in the inner cavity of the vacuum coating machine,and the electrochromic material WO₃ is evaporated onto the silver nanowire/graphene transparent conductive layer by the thermal evaporation principle to form silver nanometer.Wire/graphene/tungsten oxide thin film and PEO--LiClO₄ as a solid electrolyte were used to encapsulate the device to prepare a complete electrochromic device.Through the optical test of the silver nanowire/graphene conductive film,the electrochemical and response time of the electrochromic device were tested.The results show that the electrochromic device using graphene has better optical performance and better color purity than the electrochromic device without graphene,and its light transmittance is between 5%and 30%.With a color difference of up to25%,electrochromic devices using composite electrodes perform better than simple silver nanowire electrochromic devices.