Electroactive polymers electrochromic devices

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. 

Differendy linked carbazole derivatives possessing selenophene and pyrene (the latter not covered in this review) moieties were electropoly-merized (14EA430). The electropolymerized polymers displayed unusual properties upon electrochemical doping suggesting their potential use as electroactive layers in electrochromic devices. A typical synthesis of 2,7-diselenophenylcarbazole is shown below. 

A number of conjugated heterocyclic polymers, viz., poly(pyrrole) [9], poly(p-phenylene) [10], poly(thiophene) [11], and poly(aniline) [12] are also electrically conducting and continue to be developed and studied for electrochromic devices [13-14 see also the companion chapter in this volume] and ion switching devices [15-16], among others. Polymer films with high electrical conductivity have been generated by electrochemical polymerization of benzenoid, nonbenzenoid and heterocyclic aromatics, in particular from the derivatives of pyrrole, thiophene, carbazole, azulene, pyrene, triphenylene and aniline. The electrochemical approach for making these films is very versatile and it provides a facile way to vary the properties of the films. The realization of the applications for each electroactive polymer depends on the control and particularly the enhancement of the... 

Many typical electrochromic devices are composed of seven layers, as shown in Figure 20.4 [37]. One alternative to this classical model is a simplified five-layer electrochromic device, where transparent conducting layers were eliminated by Mecerreyes et al. (Figure 20.5) [37]. This type of configuration was successfully tested by using a solution of poly(ethylene oxide-lithium triflate) (PEO -I- CEsSOsLi) in tetrahydrofuran (THF) as a polymer electrolyte, while PEDOT was used as an electroactive polymer by Carpi and De Rossi [29]. 

An electroactive polymeric laminate suitable for an electrochromic display device comprises a conductive substrate, a first layer of an electroactive polymer, and a second layer of another electroactive polymer prepared from a monomer with a higher oxidation potential than that of the first monomer and adhering to the first layer [174]. 

Mastrogostino, M., Electrochromic devices, in Applications of Electroactive Polymers, Scrosati, B., Ed., Chapman Hall, London, 1993, 223. 

As with the absorptive/transmissive device, a complementary electrochromic polymer layer is also deposited onto the counter electrode. The device is a sandwich-type design with the counter electrode behind the working electrode, and an electrolyte layer between both. The electrochromic polymer on the counter electrode does not contribute any of its optical properties to the device, but only contributes to the balancing of the electroactive sites, allowing high Faradaic reversibility. 

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