Electrochromic materials, and devices

It Electrochim. Acta 1999, 44, 2969-3272 (a special issue for electrochromic materials and devices). 

Lampert, C. M. 1984, Electrochromic materials and devices for energy efficient windows, Solar Energy Mat. 11 11 1. 

Somani, P.R. and S. Radhakrishnan. 2002. Electrochromic materials and devices Present and future. Mater Chem Phys 77 117-133. 

Electrochromic materials and devices have been reviewed several times. Two compilations of research papers were published in 1990. An extensive treatise appeared in 1995. 2... 

Electrochromic materials and devices brief survey and new data on optical absorption in tungsten oxide and nickel oxide films. Thin Solid Films, 496, 30 36. 

Figure 33.1a illustrates the idea of the smart window. In this device a layer of electrochromic material and a layer of a transparent ion-conducting electrolyte are sandwiched between two optically transparent electrodes (OTEs). Indium-doped tin oxide on glass is used most commonly as the OTE. This material has very low... 

Bohnke, O., Applications of proton condnctors in electrochromic devices, in Proton Conductors Solids, Membranes and Gels—Materials and Devices, P. Colomban, Ed., Cambridge University Press, New York, 1992. 

Flexible electrochromic devices (ECDs) are becoming increasing important for their promising applications in many areas, such as the portable and wearable electronic devices, including smart windows, functional supercapacitors, and flexible displays. Typically, an ECD consists of four parts of substrate, conductive electrode, electrochromic material, and electrolyte. Enormous efforts have been made to improve the flexibility of ECDs including utilizing flexible polymer substrates and conductive materials. 

In the field of electrochromics, especially electrochromic displays and devices, there are various measurements undertaken to characterize the electrochromic properties of the material or device. Such measurements include in situ colorimetry, composite coloration efficiency, and electrochromic switching speed studies, along with spectroelectrochemistry [15]. 

The electrochromic performance of conducting polymers has been investigated since 1983 [7, 11-23], most of the studies having been carried out in liquid electrolyte. However, the data reported in the early papers are not exhaustive enough to evaluate the parameters necessary for the use of the electrochromic material in device technology. These data are generally of electrical response time only (i.e. the time the polymer takes to store charge) and may not be representative of electrochromic response time. 

Finally, it again should be stressed that an all solid-state configuration represents the future for large-area devices. Thus investigations of electrochromic devices using polymer electrochromic materials and polymer electrolytes offer a very fertile and almost virgin field of research. 

Duck et al. [292] have reported that poly(ethylene oxide-co-epichlorohydrin containing LiC104 has a desirable transparency and ionic conductivity at room temperature to be used as a solid electrolyte in electrochromic devices. These authors have used polyaniline and Prussian blue as an electrochromic material and have characterized the device by doublestep spectrochronoamperometry using monochromatic light at 650 nm. 

As the equilibria above show, WO3 is a cathodic electrochromic material, i.e. the darkening of the electrochromic fihn occurs at the cathode in the ceU. In contrast, I1O2 is an anodic electrochromic material, and the reversible colour change of the electrochromic device depends on proton rather than fithium ion migration ... 

For practical reasons, most electrochromic devices have a two-electrode mode of operation, with a working electrode containing the active electrochromic material, and a counter electrode, sometimes also containing an active electrochromic. A third, reference electrode may be added in devices according to prescribed electrochemical practice [891]. This yields greater applied potential control at the working electrode, but it also allows the counter electrode to experience more extreme potentials than in a two-electrode mode, which may be detrimental in many situations, and is more cumbersome overall. 

T. Timg and K. Ho. 2003. A complementary electrochromic device containing poly(3,4-ethylenedioxy thiophene) and Prussian blue. Proceedings Electrochemical Society 2003-17(Electrochromic Materials and Applications) 254r-265. 

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