Enhanced Electrochromic Smart Windows Based on Supramolecular Viologen Tweezers

Abstract

Extending the spectral response of viologen-based electrochromic devices to the near-infrared region is essential to enhance their performance for smart window applications. Although synthetic and formulation modifications have been proposed to achieve this goal, these strategies always come at the expense of deteriorating the electrochromic behavior of the system. To overcome this limitation, herein we exploited the supramolecular chemistry of viologen molecular tweezers, which undergo an intramolecular dimerization process upon reduction that leads to broad light absorption through the visible and near-infrared spectra. We observed this behavior to take place at low concentrations in a variety of electrolytic media, including solid-state ionogels that could be applied to the fabrication of electrochromic devices. Better spectral response, lower operation voltage, and higher stability were measured for these devices relative to analogous systems based on viologen monomers. As a result, when used as electrochromic smart windows, the viologen tweezer-based devices exhibited enhanced modulation of solar heat gain with reduced energy consumption, thereby demonstrating the potential of viologen supramolecular chemistry to rationally improve the performance of electrochromic devices.