Interfacial redox centers as origin of color switching in organic electrochromic device

Abstract

Fabrication and operation of simple solid state electrochromic devices using ethyl viologen diperchlorate in a polymer matrix is presented here. In-situ Raman and transmission/absorption studies have been done to establish the origin of bias induced color change, between a transparent and navy blue color, in the electrochromic device. The origin of bias induced color change has been attributed to the bias induced redox switching between its viologen dication and free redicle forms. Fundamental reason behind colour changes of viologen molecule has been established. In-situ UV-Vis spectra reveals that the navy blue color of the device under biased condition is not due to increase in the transparency corresponding to blue wavelength but due to suppression of the transparency corresponding to the complementary colors. Absorption modulation has been reported from the device with good ON/OFF contrast of the device.

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

“…Without any bias (at 0 V), device appears maroon in color whereas at 1.4 V it changes its color from maroon to blue when electrode containing P3HT is connected to positive terminal and the other electrode (deposited with EV) to negative terminal of a battery. The most probable reason for this electrochromic change is the color variation shown by P3HT and EV individually as EV is known for its bias induced color switching between transparent and blue state . When unbiased, P3HT remains in its neutral state and looks maroon whereas EV is transparent and thus the device appears maroon.…”

“…Knowing the performance of a given material helps in developing various combinations of electrochromic device where one material is used as a working electrode and other supports its counter‐part. The combination of materials gives an option to get multiple colors and thus needs investigations.…”

Chronopotentiometric Deposition of Nanocobalt Oxide for Electrochromic Auxiliary Active Electrode Application

“…A better EC counter electrode will be one which not only enables the active electrode's optical switching but also change color in the due course as it will be advantageous and will help improving the overall EC performance. [ 28 ] An EC electrode can be synthesized using electropolymerization, [ 29 ] spin coating, [ 12,14 ] drop‐casting, [ 30 ] etc. Recently, electrodes containing nanomaterials are being fabricated and found to be advantageous, [ 31 ] mainly by improving electron transport during the redox process which not only depends on the morphology but also gives an option to tailor it by appropriately designing nanomaterial‐based electrodes.…”

Mesoporous Nickel Oxide (NiO) Nanopetals for Ultrasensitive Glucose Sensing

“…When it comes to reaction-based sensing, nanomaterials could be of interest as they can provide more surface area for reaction and hence better sensing. In recent times, a variety of materials in nanostructured form have shown great potential in sensing, electronics, and optoelectronics [ 25 – 27 ]. Established fact about nanostructures is the capability of tailoring a physical property by changing its size and/or morphology which gives the versatility to the nanomaterials to be used in diverse applications.…”