Organic electrochromic materials

An important area where technology and heterocyclic chemistry combine is that of electroactive organic materials. The applications of these materials, which extend beyond simple replacements for metals, include use as conductors, superconductors, semiconductors, batteries, transistors, sensors, light emitting diodes (LEDs), and related electrochromic applications. This area is of great commercial importance. 

With regard to the importance for reversible lithium batteries and looking at the possible applications of reversible cathode materials in electrochromic (Sect. XI) and photo-electrochemical (Sect. XII) cells some significant results of this rapidly growing field should be presented. Both inorganic and organic materials are inv -gated. 

Unfortunately, organic materials are much more permeable to moisture and oxygen than metals and ceramics, for example. This is why there is a thin aluminum layer in the paper-based containers for many dairy and juice products. As mentioned previously, this is particularly important in LEDs and n-doped transistors, which are more sensitive to oxygen and water than electrochromic displays, for example. There are commercial solutions for manufacturing such a seal based on ceramics, for example, but many require vacuum processing. While compatible with roll-to-roll manufacturing, such encapsulation techniques can quickly dominate the cost of producing printed electronics. 

K-Conjugated polymers and oligomers are organic materials with many interesting and useful properties [1, 2], Examples of this class of materials include polyacetylene, polythiophene, polypyrrole, poly(phenylenevinylene) and their derivatives. Electronic conductivity, luminescence and nonlinear optical behavior are all observed in these materials and these properties have been exploited in applications such as electroluminescent devices (polymer light-emitting devices or PLEDs), electrostatic coatings, electrochromic windows, chemical sensors and memory devices [3-9]. 

The large family of thiophene-based polymers is widely used in electrochromics. Table 20.2 reports the molecular stfuctures and colors (in doped and neutral states) of several thiophene-based organic materials [29],... 

Reprinted from F. Carpi, D. De Rossi, Colors from electroactive polymers electrochromic, electroluminescent and laser devices based on organic materials. Opt. Laser Technol. 38, 292 (2006), Copyright 2006, with permission from Elsevier. 

Mortimer RJ, Dyer AL, Reynolds JR. Electrochromic organic and polymeric materials for display applications. Displays 2006 27(1) 2—18. 

Electrochromic materials undergo reversible and persistent changes of their optical properties under the action of voltage pulses. The phenomenon is known both in inorganic (oxidic) and organic materials only the former ones have been discussed in this article. Electrochromic... 

Organic thin films have been extensively investigated in connection with the attempts to apply organic materials to electronic and electrochemical devices. Phthalocyanine and its metallo-derivatives are particularly of interest in this field a wide variety of physical and physicochemical properties applicable to such devices, i.e., photo-conductivity, photovoltaic effect a, electrochromism, electrocatalysis , have been reported for their films. 

At present, intercalation compounds are used widely in various electrochemical devices (batteries, fuel cells, electrochromic devices, etc.). At the same time, many fundamental problems in this field do not yet have an explanation (e.g., the influence of ion solvation, the influence of defects in the host structure and/or in the host stoichiometry on the kinetic and thermodynamic properties of intercalation compounds). Optimization of the host stoichiometry of high-voltage intercalation compounds into oxide host materials is of prime importance for their practical application. Intercalation processes into organic polymer host materials are discussed in Chapter 26. 

Organic electrochemical processing, 9 652-685. See also Inorganic electrochemical processing cell design, 9 653-666 commercially available cells, 9 666-670 commercial processes, 9 674-681 economic aspects, 9 671-674 product recovery, 9 670-671 Organic electrochromic materials, 6 573-577... 

Stabilization of the redox cycle is relatively important in construction of potentially useful electrochromic materials, because the molecules needed for application require high redox-stability. Recently, S. Hiinig et al. proposed the concept of violene-cyanine hybrid to produce stabilized organic electrochromic materials (3). The hybrid is constructed by a violene-type redox system containing delocalized closed-shell polymethine dyes as end groups. The hybrid is expected to exhibit the color of a cyanine dye, by an overall two-electron... 

Mortimer, R.)., Organic electrochromic materials. Electrochim Acta 1999, 44, 2971-2981. 

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