KI effects on the reversible electrodeposition of silver on poly(ethylene oxide) for application in electrochromic devices

A new approach to electrochromics, based on the reversible coating-dissolution of an oxide from an inorganic electrochromic electrolyte consisting of a silver–amine complex in a polymer electrolyte (PEO), has proven successful. The reversible electrodeposition of silver onto indium–tin oxide coated glass (ITO) was investigated and the influence of HClO4 and KI was evaluated.Several characteristics of the electrolyte Ag-PEO make it suitable for use in electrochromic reversible silver electrodeposition devices, such as visible absorption spectrum with an absorbance variation of 60%, an electrochromic efficiency of 5.2 cm2 C−1 and an ionic conductivity 4.4 × 10−4 S cm−1.The addition of perchloric acid improved the transparency of Ag-PEO, and potassium iodide (KI) was fundamental in setting up the process of reversible silver electrodeposition in the PEO polymeric matrix. A description of the electrochemical processes implied is presented. A number of approaches focusing on the improvement of system performance are tested.