Sydam, Rambabu and Deepa, Melepurath and Srivastava, A. K. (2012) Electrochromic device response controlled by an in situ polymerized ionic liquid based gel electrolyte. RSC Advances , 2 (24). pp. 9011-9021. ISSN 2046-2069

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Polymer electrolytes were synthesized by two different approaches and applied to electrochromic devices based on electrodeposited tungsten oxide (WO3) or poly(3,4-ethylenedioxythiophene) (PEDOT) films as the cathode, and a Prussian blue (PB) film as the anode. The first method involved the entrapping of an ionic liquid in a polymer host (poly(methylmethacrylate) or PMMA) and the second approach relied on the in situ thermal polymerization of methylmethacrylate (MMA) in the hydrophobic ionic liquid, yielding a solidified transparent gel. The effect of in situ solid polymer electrolyte formation on device performance characteristics was realized in terms of a larger coloration efficiency of 119 cm(2) C-1 (lambda = 550 nm) achieved for the WO3-PB (MMA) device, as compared to a value of 54 cm(2) C-1 obtained for the WO3-PB (PMMA) device. Similar enhancements in electrochromic coloring efficiency, reflectance contrast, and faster switching kinetics were obtained for the PEDOT-PB (MMA) device. The strategy of introducing an electrolyte to the electrochromic device in a liquid state and then subjecting the same to gradual polymerization allows greater accessibility of the electrolyte ions to the active sites on the electrochromic electrodes and superior interfacial contact. As a consequence, larger optical contrast and faster kinetics are achieved in the MMA based devices. While PEDOT films were amorphous, PB films were semi-crystalline but only in the case of WO3; the hexagonal structure of WO3, equipped with three/four/six-coordinated voids was found to affect bleaching kinetics favorably. The performance of PMMA based electrolyte is limited by high resistance at the electrode-electrolyte interface, and a smaller number of ions available for oxidation and reduction. Large area (similar to 10 cm x 4 cm) devices were also fabricated using this simple wet chemistry method and their ability to color uniformly without any pinholes was demonstrated.

Item Type: Article
Additional Information: Copyright for this article belongs to M/s Royal Society of Chemistry.
Subjects: Chemistry
Depositing User: Users 27 not found.
Date Deposited: 02 Mar 2020 11:40
Last Modified: 02 Mar 2020 11:40

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