Fundamentals of electrochromism in metal oxide bronzes
- Tufts Univ., Medford, MA (United States)
The phenomenon of electrochromism as described here is clearly a property to be associated with a material. The material must be capable of reversible oxidation and reduction, and have an accompanying spectral change. However, since it requires a chemical change of oxidation state to occur, there must be a corresponding second material to serve as the source/sink of electrons and charge compensating ions. In short, electrochromism is observable only in a device, not in an isolated material. In its essence an electrochromic device is simply a reversible electrochemical cell, consisting of electronic conductors (the wires for an external electronic pathway), two electrodes at which the electron transfer, the oxidation and reduction, takes place, and an ion conducting and electron blocking electrolyte separating the electrode materials. There are numerous ways to combine these fundamental components and the phenomenon of electrochromism into practical devices, several of which will be described in this book. The structure of the so-called smart window has the components of the electrochemical cell assembled in the form of thin films on a transparent substrate, and is intended to be viewed in transmission. The electronic conductors in this case must be transparent, thus are labeled TC (transparent conductor). The electrochromic layer, EC, consists of a material which undergoes the color change giving rise to the electrochromic designation. The ionic conductor, IC, serves as the electrolyte to allow ion transfer and block electron transfer, preventing shorting out of the device and permitting the memory feature of retaining the coloration state upon opening the external circuit of the device. The counterelectrode layer may be either optically passive or may behave in a complementary fashion to the EC layer, e.g., be anodically coloring to the EC layer that cathodically colors. The authors study WO{sub 3} as the electrochromatic material in a smart window application.
- DOE Contract Number:
- FG36-85SF15927
- OSTI ID:
- 86743
- Report Number(s):
- CONF-8809123-; ISBN 0-8194-0069-6; TRN: IM9534%%150
- Resource Relation:
- Conference: International congress on optical science and engineering, Hamburg (Germany), 13-23 Sep 1988; Other Information: PBD: 1990; Related Information: Is Part Of Large-area chromogenics: Materials and devices for transmittance control. Volume IS 4; Lampert, C.M. [ed.] [Lawrence Berkeley Lab., CA (United States)]; Granqvist, C.G. [ed.] [Chalmers Univ. of Technology and Univ. of Gothenburg, Gothenburg (Sweden)]; PB: 618 p.
- Country of Publication:
- United States
- Language:
- English
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