Abstract: | Two donor‐acceptor systems, 4,7‐di‐2‐thienyl‐2,1,3‐benzoselenadiazole (TSeT) and 4,7‐di‐2,3‐dihydrothieno[3,4‐b][1,4]dioxin‐5‐yl‐2,1,3‐benzoselenadiazole (ESeE) are synthesized and electropolymerized to give polymers PTSeT and PESeE, respectively. One of the polymers, PTSeT, is blue‐green in the neutral state and soluble, exhibiting a deep‐red emission color. The other, PESeE, is the first 2,1,3‐benzoselenadiazole‐based neutral state green polymer with a narrow bandgap (1.04 eV). Furthermore, PESeE has superior and durable n‐ and p‐doping processes. Beyond the stability and the robustness, both of the polymer films exhibit multi‐electrochromic behavior. |