Electrochromic Devices Based On V₂O₅Films

Electrochromic device (ECD) can change its color reversibly if an external voltage is applied, it mostly consists of several layer, including a working electrode, an electrolyte layer and counter electrode. These layers have different function, so special requirement is different for each layer. Counter electrode players the role of storing and supplying ions, it should have the properties of large charge capacity and excellent electrochemical stability.Vanadium pentoxide (V2O5) has large charge capacity due to its typical layer structure, which makes it a promising material for energy storage system. It exhibits a minor transmittance change during the oxidation and reduction process and can be used as a counter electrode material in ECDs, its application is limited due to the lack of stability. The layer structure of V2O5is distorted by doping, providing more free space for lithium ions (Li+) intercalation and deintercalation, and the cyclic stability is improved.In our experiment, wet chemical methods, such as electrodepositing, spinning coating and spraying, are adopted to prepare films. A new efficient method was investigated to prepare smooth mangnese (Mn) doped V2O5films. This method used cathodic electrodeposition to dope Mn ions into V2O5structure. Compared with traditional wet chemical method, it can avoid the appearance of precipitate. Due to the colored Mn oxides and limitation of electrodepositing method for preparing large area films, titanium (Ti) was used to dope V2O5films, the addition of Ti can enhance adhesion with substrate, increase transmittance and improve stability during cyclic switching. In the process of preparing mixed solution, acetic acid was used as stabilizer to obtain clear solution. Spraying method with simple operation and low cost, which was suitable for producing large area films, was used to obtaine smooth Ti doped V2O5films.Prussian blue (PB) films with high stability and Ti doped cerium oxide (CeO2) films with excellent transmittance were also prepared by electrodepositing and spinning coating and used as counter electrodes in ECDs. Various factors, such as solution concentration, composition and solvent should be considered when chemical methods were used to prepare large area films. Smooth large area films can be obtained by selecting appropriate precursor solution, adjusting experiment parameter and controlling experiment process.Various counter electrodes were used to prepare tungsten trioxide (WO3) based ECD, optical properties, memory effect and stability were considered to analyze the advantage of these ECDs. Factors affecting these properties were also explored. This project will provide data support and important reference value for improving the properties of material and devices in the future.