A Highly Stable and Tunable Visible-Near-IR Electrochromic All-in-One Gel Device

Graphical Solid as a rock : A simple acceptor-donor-acceptor structured viologen analogue 4, 4′-(thiophene-2, 5-diyl)bis(1-methylpyridin-1-ium) diiodide was synthesized and the corresponding all-in-one gel electrochromic device (ECD) was fabricated. High electrochromic performances including large contrasts (up to 81.7 % at 570 nm), excellent color efficiency (up to 228.8 cm 2 /C at 570 nm), and extremely high stability (up to 25000 cycles) were obtained. Finally, the absorption of visible-NIR light could be adjusted selectively by varying the coloring time. Energy saving is a global topic of critical importance. Electrochromic devices (ECDs) could be used to control energy flow by modulating the light absorption reversibly upon application of a small potential bias. Herein, a visible-NIR dual-band ECD based on the viologen analogue 4, 4′-(thiophene-2, 5-diyl) bis(1-methylpyridin-1-ium) diiodide (TMP) was assembled with a simple all-in-one configuration. The TMP-based gel ECD possesses high dynamic contrast (81.7 % at 570 nm, 68.6 % at 835 nm, 62.8 % at 910 nm and 55.3 % at 1046 nm), excellent cyclic stability (70.6 % of ▵T at 570 nm maintained after 25000 cycles at 1.4 V), and low power consumption (15.2 mJ/cm 2 to complete the coloring process, 2.5 mW/cm 2 to keep color and low transmittance). Remarkably, the absorption of visible and NIR light could be selectively adjusted by varying the coloring time. For comparison, a dimethyl viologen (DMV)-based gel ECD was fabricated, and the SAR (structure-activity relationship) was established by cyclic voltammetry, density functional theory (DFT) calculations, and other electrochromic performance parameters.