The Research Of Electrochromic Materials Based On V₂O₅ And Flexible Devices

Electrochromism is the reversible and visible change in transmittance and/or reflectance associate with an electrochemically induced oxidation-reduction reaction. The electrochromic devices(ECDs) have promising applications in many fields, includes: ―smart windows‖ in cars and buildings, reusable price labels, controllable light-reflective or light transmissive display devices(for optical information and storage), controllable aircraft canopies and spacecraft thermal control, etc. All of these applications contribute to a reduction of energy consumption, increase the comfort and safety of daily life and promote the exploring of universe. Generally, a high performance ECDs should present high optical contrast, good optical memory and cyclic stability.V2O5 has attracted a broad interest over the past two decades because of its layered structure with good Li+ ions intercalation ability, the multicolor display and low voltage applied. Different from other inorganic electrochromic materials, V2O5 exhibits exceptional electrochromic behavior because it has both anodic and cathodic electrochromism properties. However, the drawbacks of V2O5 film for ECDs are poor cycle reversibility, low electrical conductivity and diffusion coefficient of Li+ ions, poor color contrast and low coloration efficiency. All of these disadvantages prevent the commercialization of V2O5-based ECDs. One effect way to improve the electrochemical and electrochromic properties of V2O5 is mixing it with other materials or combining it with other electrochromic films. And we explored a simple way for preparing the double-layer structure NiO/V2O5 as well as TiO2/V2O5 hybrid film and study the effect of the underlying NiO film with porous structure on the electrochromic properties of V2O5.1.The nanoporous NiO/V2O5 hybrid film has been successfully prepared by combining chemical bath deposition(CBD) and electrochemical deposition method. The electrochemical and optical properties of the hybrid film were investigated by cyclic voltammetry(CV), amperometric i-t, UV-vis spectroscopy and colorimetry analysis. Compared with single V2O5 electrochromic film, the NiO/V2O5 hybrid electrochromic film reveals reasonably good cyclic stability, better transmittance modulation(35% at 776 nm) and higher coloration efficiency(30.6 cm2/C at 776 nm). The noticeable improved electrochromic properties are mainly attributed to the introduction of NiO polycrystal substratewith nanoflake-like structure, which helps to strengthen the structural stability of V2O5 film and improve the performance of Li+ ions intercalation/deintercalation.2.The nanoporous TiO2/V2O5 hybrid film has been successfully prepared by combining hydrothermal and electrochemical deposition method. The electrochemical and optical properties of the hybrid film were investigated by cyclic voltammetry(CV), amperometric i-t, UV-vis spectroscopy and colorimetry analysis. Compared with single V2O5 electrochromic film, the TiO2/V2O5 hybrid electrochromic film reveals reasonably good cyclic stability, better transmittance modulation(50% at 780 nm) and higher coloration efficiency(28 cm2/C at 780 nm). The noticeable improved electrochromic properties are mainly attributed to the introduction of TiO2 nanoarry substrate with nanorod arrays structure, which helps to strengthen the structural stability of V2O5 film and improve the performance of Li+ ions intercalation/deintercalation.3. A large and flexible electrochromic device was prepared. The layer of gold film was depositedon the surface of organic membrane as a conductive substrateby the electron beam evaporation. The electrochromic film of PANI was depositedby electrochemical deposition on the surface of conductive layer. The electrochromic devices with the PANI films as working electrode and the electrode LiCl O4 gel as the electrolyte was assembled according to the sandwich structure and packaged by the hot-pressing process. Finally the electrochemical and optical properties of the electrochromic devices were tested driving by the control circuit system.