High-performance electrochromic supercapacitor based on polyoxotitanates/conjugated polymer hybrid films for visualization for the energy status

Three star-structured monomer molecules of 9-phenylcarbazole derivatives (TTCB) (TBTCB) (TECB) are synthesized and their conjugated polymer films (pTTCB) (pTBTCB) (pTECB) are prepared by electrochemical polymerization, respectively. The electrochromic (EC) properties and energy storage properties are compared of them, and the results indicate that the pTBTCB shows faster colored speed and higher cycling stability than pTTCB, as well as higher optical contrast than pTECB. Besides, the pTBTCB exhibits a high specific capacitance of 2.96 mF·cm−2 and high energy density of 0.26 mWh·cm−2, which is viewed as excellent electrochromic supercapacitor materials. We further prepare a novel hybrid thin film pTi-TBTCB with rough porous surface by electrochemical co-polymerization with TBTCB and polyoxotitanate (POT). Moreover, compared with pTBTCB, pTi-TBTCB film has higher optical contrast (45.72%), faster switching time (1.91 s, 1.26 s) and higher energy storage capacitance (4.35 mF·cm-2). Therefore, using pTi-TBTCB as electrode material, we finally prepare a prototype electrochromic supercapacitors (ECSCs), which appears blue when fully charged (1.6 V) and yellow when drained (0 V). This work further proves that polyoxotitanate can be introduced into EC films to prepare hybrid electrode materials, which can improve electrochromic and energy storage properties as electrode materials for ECSCs.