A First Truly Hydrocarbon-Based Electrochromic Molecule Exhibiting Transparent-to-Dark Switching and Heavy Atom Effect of Bromine in Color Shifting

Abstract

Electrochromic (EC) materials and devices with potential-driven optical modulation abilities have open possibilities for creating innovative and adaptive technologies. EC materials that reversibly switch from transmissive to dark or vice versa are beneficial in various applications. Though many EC materials are reported, several key issues exist, such as synthetic complexity, low reproducibility, and residual absorption. An elegant design strategy is reported here to develop a heteroatom-free, transmissive to dark electrochrome (TBF), overcoming the abovementioned challenges. Furthermore, the effect of heavy atoms on the EC properties is evaluated by substituting the bromide group with the TBF core. The synthesized molecules are electrochemically stable and reversible for 1000 continuous cycles with a coloration efficiency above 200 cm²C⁻¹ and a ∆T% of 65% for TBF and 73% for TBF-Br. The solid and gel state devices can store the imported energy that can be used to charge electronic gadgets.