ProDOT conjugated polymer-powered electrode materials: From rigid to flexible electrochromic supercapacitors

Electrochromic supercapacitors (ECSs) as one of the most stunning types of supercapacitors, which use the color fashion to monitor the stored energy level of the device still require improvements for widespread commercialization, including high performance electrode materials. This work introduces novel conjugated propylenedioxythiophene (ProDOT)-based polymers as electrode materials that concomitant showcase high coloration efficiency, optical contrast and fast switching times, while efficiently store electrical charges in both rigid and flexible ECSs. Synthesized by direct arylation polymerization, these polymers are modified with a hydrophilic oligoether and benzo-ester framework for an enhanced organosolubility, high ionic conductivity, good adherence to the working electrode support, and improved charge transfer. Notably, some key performance parameters are superior in the three-electrode set-up for the flexible ITO-coated PET electrodes modified with the current polymers, e.g. capacitance of 201 F·g −1 at 0.05 mA, coloration efficiency of 373 cm 2 ·C −1 . The incorporation of the best performing polymer into rigid/flexible ECS prototypes lead to maximum capacitance of 6.27 F·g −1 at 0.06 A·g −1 , power density exceeding 3915 W·kg −1 , and maximum energy density of 5.89 Wh·kg −1 , with better capacitive response provided by the flexible ECS. Although the rigid ECS displays faster and better EC operation, e.g. optical contrast of 55.54%, remarkable coloring efficiency of 621 cm 2 ·C −1 , the flexible counterpart which undergoes coloration transition in 5.98 s/9.82 s for bleaching/coloration with optical contrast of 38.58% and coloring efficiency of 498 cm 2 ·C, can be competitive for practical applications where flexibility and efficient operation are required, as demonstrated by its capability to preserve energy storage and electrochromic performance in bent position. As addition, four series connected ECS prototypes are able to power a red LED, validating our work. • Two functionalized ProDOT polymers are obtained by direct arylation polymerization. • These show distinct morphology & wettability, and high thermal and redox stability. • Dual functionality of polymers as electrochrome & energy-storage material is proven. • Best performing polymer is used in rigid/flexible electrochromic supercapacitors. • Coloration efficiency of 621 cm 2 ·C −1 and capacitance of 6.27 F·g −1 are obtained.