am6b11321_si_001.pdf (2.89 MB)
Colorless to Neutral Color Electrochromic Devices Based on Asymmetric Viologens
journal contribution
posted on 2016-10-11, 00:00 authored by Yolanda Alesanco, Ana Viñuales, Germán Cabañero, Javier Rodriguez, Ramón Tena-ZaeraElectrochromic
materials have extensively been investigated because of their potential
fields of application, with a significant growing interest in expanding
the provided colorations. However, among all palette of colors, colorless
electrochromic devices (ECDs) that provide neutral-grayish colorations
with a simple configuration remain a key challenge. The present study
reports on the synthesis of asymmetrically 1-alkyl-1′-aryl-substituted
viologens and their incorporation in PVA-borax gel polyelectrolytes
for ECDs that constitute the simplest device architecture (glass/TCO/EC
gel/TCO/glass). We demonstrate herein that these EC gels based on
single asymmetric viologens provide more neutral-colored state than
their corresponding symmetric viologens (a* and b* ≤ |15|), while maintaining satisfactory colorless
bleached state (%Tb > 70% in the whole
visible range), transmittance changes (i.e., ∼60%) and cyclability
(i.e., ∼15 000 cycles). Additionally, the effect of
the solvent on the observed coloration has also been investigated.
This easy-to-make neutral-grayish color ECDs may significantly extend
the potential of the electrochromic technology, because they adapt
better aesthetically to the surrounding environment, as they are easier
to implement in different applications.