Heat resistant polymer electrolyte for enhanced organic electrochromic windows based on poly (3,3-dimethyl-3,4-dihydro-2
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Heat resistant polymer electrolyte for enhanced organic electrochromic windows based on poly (3,3-dimethyl-3,4-dihydro-2H-thieno[3,4b][1,4]dioxepine) Nishita Anandan1, Sooyeun Kim1, Minoru Taya1 1
University of Washington, Seattle
ABSTRACT Electrochromic Windows(ECWs) have the potential to save energy through dynamic control of light and solar energy entering a room (via solar heat gain coefficient control). ECWs have been developed as an optical shutter in airplane, building and automobile applications. An ECW is composed of three components, a working electrode based on electrochromic materials, a counter electrode based on ion storage materials and the electrolyte as an ionic conducting layer. Organic ECWs have been gaining popularity due to easy and cost effective manufacturing, availability of wide range of colors, high optical contrast and flexibility in design. However there are challenges in commercialization and application of organic ECWs. The application of ECWs as a sunroof in automobiles demands operation in harsh environment conditions like elevated temperature. Consequently the University of Washington, Center for Intelligent Materials and Systems has been developing a heat resistant organic ECW that can be operated at elevated temperatures maintaining high optical contrast, fast switching speed, optical color memory and electrochemical stability. The proposed design is an ECW based on poly (3,3-dimethyl-3,4dihydro-2H-thieno[3,4-b][1,4]dioxepine),PPRODOT-Me2 as a working electrode, V2O5-TiO2 composite materials as a counter electrode and poly(ethylene imine) based electrolyte. The ionic conductivity of the electrolyte was calculated through complex impedance method and temperature dependence of the electrolyte was determined using environment test chamber to control a temperature range of 15 to 80o Celsius for 100 hours. A 76 × 76 mm2 ECW was developed and the optical transmittance change was observed by Chronoamperomerty and Time course measurement. The electrochemical stability of the window was monitored using cyclic voltammetry. The developed electrochromic window showed good optical contrast, electrochemical stability and fast response time after testing at elevated temperatures for 100 hours. INTRODUCTION An electrochromic window(ECW) is a device with a potential to change its optical properties in a reversible and persistent way under the action of a voltage pulse. Generally, ECWs are composed of three components, an electrochromic material as the working electrode, ion storage material as the counter electrode to maintain electrochemical stability and the electrolyte with high ionic conductivity sandwiched between the working and counter electrode. The aim of this paper is to develop organic ECWs capable of being used as sunroof in automobiles. One of the major challenges in this application is that the ECW should sustain and operate at elevated
temperatures since the temperature of sun roofs in automobiles parked under the sun can reach up to 80oC. In this paper, (3,3-dimethyl-3,4-dihydro
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