Air-stable, high contrast solution-phase electrochromic device based on an A-D-A viologen derivative

Electrochromic (EC) devices with reversible transmittance switching have promising prospects in the applications of photoelectric displays. Herein, a novel air-stable and high contrast solution-phase electrochromic device based on new viologen derivative (DPB) with A-D-A structure (A: acceptor; D: donor) was demonstrated. Devices possessed simple configuration of ITO/EC solution/ITO. Ferrocene and polycarbonate (PC) were selected as the complementary material and solvent, respectively. All of the fabrications and performance testing work were conducted in normal air condition. The DPB-based device showed deep magenta color in colored state and exhibited high optical contrast of ΔT of 72.2% (517 nm) and good coloration efficiency of 102.2 cm2/C at 1.8 V. The device appeared only slight degradation of ΔT (ΔT = 69.6% or retained 96.7% of its initial ΔT after 5000 s constant switching) under the normal air atmosphere, which was even better than some reported well-packaged viologen-based solution ECDs. Additionally, the UV–vis reflective spectra were also conducted to assess the reflectance property of the devices. The reflectance peak (ΔR = 2.6%) and absorption peak matched accurately, which indicated that the new viologen derivative possesses the potential application in reflective electrochromic devices.