Solid-State Supercapacitor Constructed with Organic Electrochromic Electrodes Based on Dithienothiophene and 3,4-Ethylenedioxythiophene

Capacitive and electrochromic behaviors of electrodeposited poly{4,4′-[2,6-bis(2,3-dihydrothieno[3,4-b][1,4]dioxin-5-yl) dithieno[3,2-b:2′,3′-d]thiophene-3,5-diyl] dibenzonitrile}, P[E-CNDTT-E], are reported. The morphological, structural, and electrochemical properties of the polymer are determined by atomic force microscopy, Fourier transform infrared, cyclic voltammetry, spectroelectrochemical measurements, electrochemical impedance spectroscopy, and galvanostatic charging/discharging measurements. Theoretical calculations support the planarity of the structure through O···S interactions, which allow the polymer to have a low band gap of 1.43 eV. P[E-CNDTT-E] has a high capacitance of 223 F g^-1 at the current density of 1 A g^-1 and displays a color change from purple to gray with an optical contrast of 30% and a coloration efficiency of 450 cm² C^-1 upon applying cathodic potential. The solid-state supercapacitor is constructed, which has a high specific capacitance of 63 F g^-1 and a significant energy density of 6.5 W h kg^-1. Additionally, the device retains 90% of its capacitance after 8000 cycles.