One-step electropolymerized thieno[3,2-b]thiophene-based bifunctional electrode with controlled color conversion for electrochromic energy storage application

The development of novel visual energy storage devices that can in real time estimate or determine the storage of electrical energy is central to the emerging next-generation wearable electronics. However, such integrated visual energy system requires the electrode materials to possess both electrochromic and supercapacitive properties. In this work, we provide bifunctional electrodes based on copolymer poly(thieno[3,2-b]thiophene-co-3,4-ethylenedioxythiophene) (P(TT-co-EDOT)) via straightforward one-step electrochemical copolymerization process, which are endowed with favorable supercapacitive and electrochromic properties. Benefited from the synergistic effect of PTT and PEDOT, the prepared copolymer films exhibit good flexibility and conductivity, and mechanical stability under long-term deformation. Moreover, the morphology and electrical performance of the P(TT-co-EDOT) can be facile modulated by simultaneously depositing thieno[3,2-b]thiophene (TT) and 3,4-ethylenedioxythiophene (EDOT) with different ratio. The resulting P(TT-co-EDOT) electrodes achieve high specific capacitance (193 F g−1 at 4 A g−1), a large optical contrast (50.2%), recognizable color conversion and color tunability. This work paves a simple way for the development of thiophene-based conducting polymers in the field of flexible and emerging electrochromic energy storage devices.