Live spectroscopy to observe electrochromism in viologen based solid state device

Tanwar

et al. 2021

IET Nanodielectrics

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A nanostructured film of NiCo 2 O 4 has been prepared using a hydrothermal technique by simply using separate precursors to obtain nanoneedle-like architecture for electrochromic applications. A homogeneous film consisting of packed nanoneedles with moderate density, appearing translucent white in colour, has been obtained and characterized using XRD and Raman spectroscopy techniques for confirming the composition and structure. Electrochemical analysis of the film reveals that the film shows good electrochromic properties under the anodic scan of potential with strong stability. The mechanism of the electrode under the transformation from natural white to opaque dark brown colour has been understood with the help of an in situ optical absorption spectroscopy technique. The electrode is found electrochromically active with a bias of up to 2 V and shows 50% optical contrast which makes it a good candidate for application in a solid state electrochromic device. This is an open access article under the terms of the Creative Commons Attribution-NonCommercial-NoDerivs License, which permits use and distribution in any medium, provided the original work is properly cited, the use is non-commercial and no modifications or adaptations are made.

Section: Resultsmentioning

confidence: 72%

Low voltage colour modulation in hydrothermally grown Ni‐Co nanoneedles for electrochromic application

Tanwar

et al. 2021

IET Nanodielectrics

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“…This is in consonance with the above‐mentioned hypothesis as the P3HT is maroon in its neutral state whereas EV +2 is transparent, so overall the device is maroon in OFF state. When the device is turned ON (at 1.4 V), Raman peaks at 1029, 1359, 1530and 1658 cm −1 the modes of cationic form of EV radical (EV + • ), is present which is blue in color. In addition to this, there is a peak at 1470 cm −1 corresponding to oxidized P3HT which is pale blue in color, overall giving the blue appearance to the ON device as can be seen in photograph in the inset (Figure b).…”

Section: Resultsmentioning

confidence: 99%

Enhancing Viologen's Electrochromism by Incorporating Thiophene: A Step Toward All‐Organic Flexible Device

Physica Status Solidi (a)

Mishra

et al. 2018

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An all-organic electrochromic device seems to be a possibility with ethyl viologen (EV) and poly-3-hexylthiophene (P3HT), both being organic materials, showing complementary electrochromic pair for color switching. The EV-P3HT layer, sandwiched between ITO-coated glass substrates shows switching between maroon and blue with an applied bias of 1.4 V. Mechanism of the color switching has been examined using UV-Vis and Raman spectroscopies. The fabricated device shows optical modulation of 80%, switching time of 1 s while maintaining cycle life for a period of more than 600 s. The paradigm reported here inches toward realizing a flexible all-organic electrochromic device.

“…On the other hand, the ON device (with 1 V bias) transmission of 450 nm wavelength (corresponding to blue color) appears prominent (red curve, Figure 3) giving the blue appearance to the device in this state. An excellent optical contrast of 56% has been estimated from the device at 400 nm wavelength gives another indication, other than the low operating voltage as compared to other EVbased devices, 42,44,45 of the improved electrochromic performance of the FPP−EV solid state device. It is evident here that the introduction of the custom-designed electron-rich FPP with n-type electrochromic EV seems to be an apparent reason for augmentation in the electrochromic performance of the present device with bias-induced mutual redox change being the most probable mechanism for color switching.…”

Section: ■ Results and Discussionmentioning

confidence: 92%

Electron Donor Ferrocenyl Phenothiazine: Counter Ion for Improving All-Organic Electrochromism

Poddar

ACS Appl. Electron. Mater.

et al. 2020

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Electron-donating properties of 3-ferrocenylethynyl-10-propyl-10H-phenothiazine (FPP) has been studied to be used as an efficient counter ion for application in a viologen-based organic electrochromic device to facilitate an efficient all-organic electrochromic device. The FPP molecule, when used as a counter ion with viologen, improves the switching time to less than half a second and exhibits lower operation voltage of ∼1 V and excellent stability for longer than 1800 s with a negligible amount of absorption loss. Spectroscopic and electrochemical measurement techniques have been used to understand the mechanism of bias-induced enhanced performance of the FPP−viologen-based solidstate electrochromic device. The device does not contain any liquid electrolytic medium to support its switching behavior and can also be fabricated on a plastic substrate for realization of a flexible all-organic electrochromic device. The viologen−FPP electrochromic device showed an optical contrast of more than 55% with a bias of 0 to 1 V when switched between OFF-(transparent) and ON-(blue) states. An excellent value of coloration efficiency of 460 cm 2 /C is obtained with a simple all-solid device geometry arrangement, making it the most efficient solid-state electrochromic device in the viologen family of devices.