Design of robust fluorinated interpenetrating poly(thieno[3,2-b]thiophene) network for highly stable flexible electrochromic-supercapacitor devices

Owing to the capability of real-time feedback on energy storage status through reversible color changes, electrochromic-supercapacitor (EC-SC) devices have shown great potential for various applications in future intelligent electronics. However, despite recent advances, the development of EC-SC devices with high electrochromic performance, cycling stability, and mechanical flexibility remains a lingering challenge. Here, we propose an efficient interpenetrating conjugated network design strategy to prepare robust high-performance polythiophene EC-SC materials by introducing tough intermolecular hydrogen bonding through fluorination on poly(thieno[3,2-b]thiophene) backbone. The obtained EC-SC material poly(3-(4-fluorophenyl)thieno[3,2-b]thiophene) (PFPTT) simultaneously achieves high electrochromic performance (48 % optical contrast at 480 nm with coloration efficiency of 208 cm2 C−1), favorable specific capacitance (120F g−1, 1 A g−1), and outstanding cyclic stability (<6% reduction after 10,000 doping/dedoping cycles). Enabled by the superior performance of PFPTT, we further fabricate its-based flexible electrochromic-supercapacitor devices (FESD) for real-time feedback of energy storage status. Such FESDs are demonstrated to exhibit reversible tan and blue changes against mechanical bending, as well as excellent stability by retaining 85 % specific capacitance after 3000 charging/discharging cycles. The interpenetrating conjugated network design strategy, together with the resultant stable high-performance PFPTT materials, are promising for the development of reliable FESD and their further applications like wearable electronics.