Studies Of Photoelectric And Electrochemical Properties For Modified-vanadium Pentoxide Films

The optical properties of electrochromic materials with semiconducting nature change under the action of an applied electric field or an electric current. It has drawn great attention for the applications in smart windows and light shutters. Vanadium pentoxide, with high coloration efficiency and wide color variation, has been considered as the most potential material for preparation of the electrochromic device. However, their promotion and application has been limited by the slow reaction of color variation. Therefore great efforts have been made in order to improve or modify their electrochromic property. And the study to optimize the process structure and modify the host material is regarded as the most effective method to improve the color change reaction rate. The main contents are listed as follows:（1） The process of preparation of vanadium pentoxide films: The preparation of vanadium pentoxide films has been investigated and it is found that the thickness and the transmittance of the film varies with the electrodeposition time and the concentration of sol.It is suitable for the preparation of electrochromic devices when the concentration is 0.05mol/L and the electrodeposition time is one hundred seconds, because in this conditions the thickness of Vanadium pentoxide films with the widest range of optical modulator is 400 nm.（2） The electrochromic devices of graphene intercalated vanadium pentoxide films: The graphene, prepared by redox method, was mixed with V₂O₅ sol to prepare graphene/V₂O₅ composite films by electrodeposition. Composite films were characterized by X-ray diffraction（XRD） testing, the results showed that graphene entered into V₂O₅ interlayer and the interlayer spacing was propped open. Cyclic voltammetry and chronoamperometry curve were used to characterize the electrochemical properties of the films. The results showed that adding graphene improved the cycling stability and the response rate of the films. Compared to V₂O₅ films, electrochromic properties of the composite films had significantly improved.The composite film is used to assemble the electrochromic device,which shows a variety of color changes at different voltages, and has good cycle stability.（3） Composite Photoelectrochromic film was prepared by direct intercalation of dye and PEO inside the layered structure of vanadium pentoxide. In this method electrochromic device was constructed and its electrochromic properties has been studied. We found that the device become darker in the light conditions, which bring convenience to the preparaton of the electrochromic device.