A novel ionic liquid with stable radical as the electrolyte for hybrid type electrochromic devices

An ionic liquid (IL), 1-butyl-3-{2-oxo-2-[(2,2,6,6-tetramethylpiperidin-1-oxyl-4-yl)amino]ethyl}-1H-imidazol-3-ium tetrafluoroborate (TILBF4), containing a stable radical, 2,2,6,6-tetramethyl-1-piperidinyl-oxy (TEMPO), was synthesized successfully. The TILBF4shows two distinctive properties having the characteristics of ion-storage and supporting electrolyte materials. In this study, a hybrid electrochromic device (ECD) with a high coloration efficiency based on this TILBF4and a poly(3,3-diethyl-3,4-dihydro-2H-thieno-[3,4-b][1,4]dioxepine) (PProDOT-Et2) thin film was proposed. The maximum absorbance of the PProDOT-Et2/TILBF4ECD was noticed at 590?nm upon applying the cell potential between ?1.0 and 1.0?V. The device exhibits a transmittance change (£GT) of 62.2% at 590?nm when being switched in the first transition, with short switching times of 4.0?s for bleaching and 3.6?s for coloring. A relatively high coloration efficiency (£b) of 983.0?cm2/C was achieved at 590?nm. Furthermore, the ECD maintained 98.0% of its initial £GT after consecutive operation for 1000 cycles between ?1.0 and 1.0?V. ? 2017 Elsevier B.V.