Electrochromism glasses

Redox series of metal-polypyridines still await their practical exploration. The existence of multistep, reversible, sequential reduction processes, each step occurring at a defined potential and being localized at a specific molecular site, is very promising for possible applications in molecular electronics. This would require to organize the active complexes in films, polymers or supermolecules. Up to now, only the electrochromic behavior of some [Ru(N,N)a] + complexes has been explored with potential applications in electrochromic glasses, displays and redox sensors [206, 262, 264]. 

Walls of windows are commonplace in modem office blocks use of electrochromic glass improves energy efficiency and working enviroirment. 

Fast-Ion-Gonducting Glasses. One possible appHcation of fast-ion-conducting glasses is in soHd-state batteries (qv) for automobiles. The glasses might also be used in electrochromic displays or as sensors (qv) (25). 

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... 

Spatial electrochromism has been demonstrated in metallopolymeric films.28 Photolysis of poly-[Run(L10)2(py)2]Cl2 thin films on ITO glass in the presence of chloride ions leads to photochemical loss of the photolabile pyridine ligands, and sequential formation of po/y-[RuII(Llt))2(py)Cl]Cl and po/y-[Run(L10)2Cl2] (Scheme 1). 

The LB technique is amenable to the fabrication of ECDs as demonstrated by the report of a thin-film display based on bis(phthalocyaninato)praseodymium(III).75 The electrochromic electrode in the display was fabricated by deposition of multilayers (10-20 layers, r+00-200 A) of the complex onto ITO-coated glass (7 x4cm2) slides. The display exhibited blue-green-yellow-red polyelectrochromicity over a potential range of —2 to +2V. After 105 cycles no significant... 

In situ UV-visible spectroscopy monitors the energy of electrons within the analyte. While, strictly speaking, all materials change their UV-visible spectrum in accompaniment with electrode reactions (they are said to be electrochromic), the majority of these changes are not discernible by the human eye, and therefore may not be useful to the analyst. Electrodes must be optically transparent for in situ work, with the most commonly used being a thin film of the semiconductor, indium-tin oxide, on glass. 

In order to take advantage of nanometer-sized semiconductor clusters, one must provide an electron pathway for conduction between the particles. This has been achieved by sintering colloidal solutions deposited on conductive glasses. The resulting material is a porous nanostructured film, like that shown in Fig. 1, which retains many of the characteristics of colloidal solutions, but is in a more manageable form and may be produced in a transparent state. Furthermore, the Fermi level within each semiconductor particle can be controlled potentiostati-cally, a feature which is fundamental for the functioning of the electrochromic devices described in Section III. 

Vroon, Z. Spee, C. Sol-Gel Coatings on Large Area Glass Sheets for Electrochromic Devices. J. Non-Cryst. Solids 1997, 218, 189-195. 

As its name implies, electrochromic materials change color as a result of an injection of electrons. The typical ECD has a number of layers, sandwiched between glass (Figure 2.52a). When no voltage is applied to the device, the incoming light... 

Nickel(II) oxide crystallizes in the NaCl structure. Thin amorphous films of it exhibit electrochromic behavior and are antiferromagnetic at Tn = 247 °C. Nickel(II) oxide films with smooth surfaces and columnar structures of preferred (100) orientation on MgO(lll), Si(lll), soda lime glass, fused silica and stainless steel can be obtained by and... 

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