In Situ Colorimetric Analysis of Electrochromic Polymers and Devices

Abstract

We report a colorimetric method for the in situ study of electrochromic polymers based on the CIE system of colorimetry. This method is useful for the comparison of the electrochemical and optical properties of conjugated polymers, and for gaining control of the color of dual polymer electrochromic devices. Twelve electrochromic polymers were investigated using in situ colorimetric analysis in order to define their CIE coordinates and electrochemical potential windows. By controlling the electron density and steric interactions along conjugated polymer backbones, we have developed a set of electrochromic polymers that provides colors throughout the full range of color space. The applicability of the method is illustrated with a model dual polymer device based on poly(2-(3,4-ethylenedioxy)thienyl(biphenyl)) (PBEDOT-BP) and poly(3,6-bis(3,4-ethylenedioxy)thienyl)-N-methylcarbazole) (PBEDOT-NMeCz). This device yields green/brown colors (L* = 48, a* = 0, b* = 20 and L* = 44, a* = 6, b* = 26) interesting for earthtone and natural vegetation chameleon materials when the charge states of the two polymers are reversed. This technique is a convenient method for reproducibly fine-tuning the color of electrochromic materials, while reducing trial and error in the process of electrochromic device development.

In situ spectroelectrochemistry and colour measurement of a complementary electrochromic device based on surface-confined Prussian blue and aqueous solution-phase methyl viologen

“…For application in the field of electrochromism, in 2000 Reynolds and co-workers introduced an in situ colour measurement ('colorimetry') method for the precise measurement and control of colour in electrochromic materials and ECDs [16]. This methodology, with use of a simple portable colorimeter, has since been extensively applied to colour measurement of numerous electrochromic conjugated polymer films and devices , thin films of PB [9], a viologen-based electrochromic plastic device [40], and the n-heptyl viologen system [41].…”

Improving the color switch contrast in PEDOT:PSS-based electrochromic displays

“…In order to simulate and evaluate the color contrast of reflective displays, coloration efficiency or transmittance measurements are often employed [22,23], but here a colorimetric method based on the CIE L*a*b* color system is used [24,25]. In contrast to e.g.…”

Switchable window based on electrochromic polymers

“…5 Electrochromic materials can be divided into many different classes. Some of the more heavily researched classes include both the inorganic and organic systems, such as transition metal oxides and polynuclear transition metal hexacyanometallates, and the organic systems, viologens and conducting polymers.…”