Flexible energy storage device fabricated by electrochromic smart copolymer based on thienothiophene-triphenyamine and EDOT

Sustainable energy storage materials are of increasing importance for new energy technologies to produce more intelligent, lighter, thinner and multifunctional power systems. In this study, copolymers of N-(4-(4-thieno[3,2-b]thiophene-3-ylphenyl)phenyl)-N-phenylbenzenamine (TTpTPA) and 3,4-ethylenedioxythiophene (EDOT) were synthesized electrochemically starting from different molar ratios of TTpTPA(T) and EDOT(E) (n_T:n_E). The copolymers obtained on the ITO surface, i.e. P(T10-1E), P(T5-1E), P(T5-2E), P(T1-1E), were directly used to design electrochromic energy storage devices (ECESDs). Electrochemical characterizations suggested that the copolymerization improved the capacitances of PTTpTPA and PEDOT up to the highest value of 21 mF cm⁻² with the copolymer P(T1-1E). It exhibited a color change from purple to blue during charging and discharging processes. Additionally, P(T5-2E) displayed a remarkable multicolor change as a color cartel, i.e. red, yellow, green, gray and blue, during the oxidation with a high color efficiency of 161 cm²C⁻¹. Finally, the flexible symmetric device prototype of P(T1-1E) possessed a good practical application for next generation energy storage devices with its high energy and high-power densities.