Thomas G. Rukavina

Tungsten Oxide‐Prussian Blue Electrochromic System Based on a Proton‐Conducting Polymer Electrolyte

A new solid-state electrochromic system is presented. It is transparent and is comprised of a tungsten oxide and Prussian blue (PB) thin film couple in combination with a proton-conducting, solid polymer electrolyte. This electrochromic system exhibits rapid and deep optical switching; characteristics of a complementary configuration, both electrochromic films color and bleach in phase. Complementary electrochromic cells with the tungsten oxide-PB couple have previously been based on Li[sup +] or K[sup +]-conducting electrolytes. A repetitively cycling cell has not previously been reported with a proton-conducting solid polymer electrolyte. The devices were operated at low applied voltages, +1.2 V to darken and [minus]0.6 V to bleach. Repeated reduction and oxidation of the current system over 20,000 cycles has been demonstrated, indicating a large number of switchings without great degradation or irreversible side reactions. The sustained, high overall coloration efficiency of the devices suggests the insertion/extraction of protons into and out of both WO[sub 3] and PB films. The effects of cell size and operating temperature on the switching response are discussed.

Lithium ion conductors and proton conductors: Effects of plasticizers and hydration

Abstract Lithium ion conductors and proton conductors were developed in support of a large-area electrochromic transparency effort with the goal of identifying a polymer electrolyte that provides high ionic conductivity with good electrochemical and thermal stability. The best lithium ion conductor was found to be a transparent, solid uv -curable poly(alkyleneoxy)acrylate-LiCF 3 SO 3 complex that has excellent thermal stability, and room temperature ionic conductivity on the order of 10 −6 S cm −1 . The addition of 50 wt.% propylene carbonate to the polymer-salt complex increases its conductivity by three orders of magnitude, without degradation of its other physical properties. Two sulfonic acid-based polyelectrolytes were explored as potential proton conductors, a cross-linked poly(2-acrylamido-2-methyl-1-propane sulfonic acid), PAAMPS, which has practical use for temperatures up to about 70 °C, and a novel vinyl sulfonic acid/vinylpyrrolidone copolymer that has excellent thermal stability for over 1000 h at 90 °C. The copolymer has the potential for high conductivity based on its relatively low equivalent weight. Two different electrochromic devices containing the polymer electrolytes are described, and the temperature-dependent switching behavior of the devices is related to the conductivity of the polymer electrolytes.