Solid state electrochromic cells

By combining an electrically conductive polymer (e.g. POT) prepared by spin coating from solution with a solid polymer electrolyte and a metal oxide, a sohd state electrochromic device is constructed [713]. Substrates coated with PT can be used in electrochromic displays, in solar cells (cf Sect. 6.3), and for corrosion protection [714]. Poly(3,4-ethylenedioxythiophene-2,5-diyl), which has good electrochromic properties, (for structure cf Sect. 1.2) can used as an electrode in a solid state electrochromic cell (cf Sect. 3.4.3) [43]. PITN can be reversibly cation- and anion-doped without decomposition. This polymer, with... 

BOHNKE, o., ROUSSELOT, c., GILLET, P.A., TRUCHE, c.. Gel electrolyte for solid-state electrochromic cell,/. Electrochem. Soc., 1992,139,1862-5. 

Figure 14.8 Optical absorption spectra of a PEDOT electrochemical cell for different applied voltages. Reprinted from j. C. Custafsson, B. Liedberg and O. Inganas, In situ spectroscopic investigations of electrochromism and ion transport in a poly(3,4-ethylenedioxythiophene) electrode in a solid state electrochemical cell, Solid State Ionics 69, 145-152 (1994), Copyright 1994, with permission from Elsevier...

A solid state electrochromic device can be constructed by combining a thin layer of an electrically conductive polymer like 3-octylPT produced by spin coating from solution with a solid polymer electrolyte and a metal oxide [175]. Substrates coated with PT have been claimed for use in electrochromic displays, in solar cells and for corrosion protection [185]. 

AVELLANEDA, c., VIEIRA, D., AL-KAHLOUT, A., et aZ., All solid-state electrochromic devices with gelatin-based electrolyte. Solar Energy Mater. Solar Cells, 2008, 92, 228-33. 

There is a large potential for conducting polymers as corrosion-inhibiting coatings. For instance, the corrosion protection ability of polyaniline is pH-dependent. At lower pH polyaniline-coated steel corrodes about 100 times more slowly than noncoated steel. By comparison, at a pH of about 7 the corrosion protection time is only twice for polyaniline-coated steel. Another area of application involves creation of solid state rechargeable batteries and electrochromic cells. Polyheterocycles have been cycled thousands of times with retention of over 50% of the electrochromic activity for some materials after 10,000 cycles. IR polarizers based on polyaniline have been shown to be as good as metal wire polarizers. 

Solid-state electrochemistry is an important and rapidly developing scientific field that integrates many aspects of classical electrochemical science and engineering, materials science, solid-state chemistry and physics, heterogeneous catalysis, and other areas of physical chemistry. This field comprises - but is not limited to - the electrochemistry of solid materials, the thermodynamics and kinetics of electrochemical reactions involving at least one solid phase, and also the transport of ions and electrons in solids and interactions between solid, liquid and/or gaseous phases, whenever these processes are essentially determined by the properties of solids and are relevant to the electrochemical reactions. The range of applications includes many types of batteries and fuel cells, a variety of sensors and analytical appliances, electrochemical pumps and compressors, ceramic membranes with ionic or mixed ionic-electronic conductivity, solid-state electrolyzers and electrocatalytic reactors, the synthesis of new materials with improved properties and corrosion protection, supercapacitors, and electrochromic and memory devices. 

Polymer electrolytes are also sought for a variety of other applications such as sensors, electrochromic devices and photoelectrochemical cells. The ambient temperature operation of many of these requires conductivities of the same magnitude as for batteries. The need for high electrolytic conductivity stems from the fact that the rate at which the solid-state devices can be operated, for example, how fast energy from a Li battery can be drained or the colour of an electrochromic window can be switched, depends to a large extent on the mobility of ionic charge carriers, hence... 

Cinnseleach R., Boschloo G., Rao S.N., Fitzmaurice D. Electrochromic windows based on viologen-modified nanostructured Ti02 films. Sol. Energy Mater. Sol. Cells 1998 55 215-233 Cogan S.F., Plante T.D., Parker M.A., Rauh R.D. Electrochromic solar attenuation in crystaUine and amorphous Li WOs. Sol. Energy Mater. Sol. Cells 1986 14 185-193 Coleman J.P., Lynch A.T., Madhukar P., Wagenknecht J.H. Antimony-doped tin oxide powders Electrochromic materials for printed displays. Sol. Energy Mater. Sol. Cells, 1999 56 375-394 Corr D., Bach U., Fay D., Kinsella M., McAtamney C., O Reilly F., Rao S.N., Stobie N. Coloured electrochromic paper-quality displays based on modified mesoporous electrodes. Solid State Ion. 2003 165 315-321... 

Granqvist C.G. Electrochromics and smart windows. Solid State Ion. 1993 60(1-3) 213-214 Granqvist C.G. Handbook of Inorganic Electrochromic Materials, Elsevier, Amsterdam, 1995 Granqvist C.G., Electrochromic tungsten oxide films Review of progress 1993-1998. Sol. Energy Mater. Sol. Cells 2000 60 201-262... 

Macfarlane D.R., Sun J., Forsyth M., Bell J.M., Evans L.A., Skryabin I.L. Polymer electrolytes for electrochromic window applications. Solid State Ion. 1996 86-88 959-964 Maheswari S.P., Habib M.A. Electrochromic aspects of phosphotungstic acid. Sol. Energy Mater. Sol. Cells 1988 18 75-82... 

The future prospects for polymer electrolytes look promising because it has been appreciated that they form an ideal medium for a wide range of electrochemical processes. Other than primary and secondary batteries, and high and low temperature fuel cells, practical applications for polymer electrolytes that are under consideration include electrochromic devices, modified electrode/sensors, solid-state reference electrode systems, supercapacitors, thermoelectric generators, high-vacuum electrochemistry and electrochemical switching. Device applications that have been the main driving force behind the development of polymer electrolytes are treated hereafter. 

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