Electrocatalytic PProDOT–Me2 counter electrode for a Br-/Br3- redox couple in a WO3-based electrochromic device

Abstract A new electrochromic device (ECD) was fabricated, consisting of poly(3,4-(2,2-dimethyl-propylenedioxy)thiophene) (PProDOT–Me2) and tungsten trioxide (WO3) films. The conventional cathodic EC material PProDOT–Me2 acts as an electrocatalytic counter electrode here, working with an electrolyte which contains the Br-/Br3- redox couple to accelerate the electrochromic process and lower the driving voltage of the ECD. The device can be fully colored at under -1.0 V and self-bleached at 0 V (in a short-circuited state) with high optical modulation of 72.4% at 680 nm. Compared with other self-bleaching devices, the response time of 5.6 s for coloring and 15.3 s for bleaching suggests an exceptional switching speed. Additionally, the coloration efficiency (CE) of the device reaches 88.9 cm2/C. When the long-term stability of the device was evaluated, no apparent deterioration was observed after 5000 cycles.