Electrochromic Thin-film Deposition on the ITO Glasses by Colloidal Vanadium Pentaoxide Sol

Abstract

An electrochromic V₂O₅ film has been deposited onto a glass coated with an In₂O₃: Sn layer (ITO glass) and its electrochromic properties have been examined.
An aqueous solution of ammonium metavanadate (1/40 mol⋅dm-3) was passed through a cationexchange column to obtain monomeric decavanadic acid. Then it was concentrated by rotary evaporator and allowed to stand at 40°C for 100h. The monomeric decavanadic acid solution was gradually condensed to become a dark reddish, viscous colloidal solution of V₂O₅. This sol was then coated on the ITO glass and dried at 60°C. The V₂O₅ coated ITO glass was alternatively polarized anodically or cathodically in propylene carbonate-1 mole dm-3 lithium perchlorate mixture. On anodic polarization, orange color appeared, while on cathodic polarization, the color of green to gray appeared, reversibly.
Electron microscopic observation disclosed a th in oxide film with fibril structure of V₂O₅ microcristallites closely entangled with each other. These fibrils had a size of about 10 nm in diameter and about 1 pm in length, and contained an appreciable amount of water (about 15%by weight).