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

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/cm2 to complete the coloring process, 2.5 mW/cm2 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.